Variation in the serotonin transporter genotype is associated with maternal restraint and rejection of infants: A nonhuman primate (Macaca mulatta) model

Elizabeth K. Wood; Zachary Baron; Ryno Kruger; Colt Halter; Natalia Gabrielle; Leslie Neville; Ellie Smith; Leah Marett; Miranda Johnson; Laura Del Rosso; John P. Capitanio; J. Dee Higley

doi:10.1371/journal.pone.0281935

Peer Review History

Original SubmissionOctober 3, 2022
1 Dec 2022 Decision Letter - Tamas Kozicz, Editor PONE-D-22-27260Variation in the serotonin transporter genotype is associated with maternal restraint and rejection of infants: A nonhuman primate (Macaca mulatta)modelPLOS ONE Dear Dr. Wood, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. When revising your manuscript, please consider all issues mentioned in the reviewers' comments carefully: please outline every change made in response to their comments and provide suitable rebuttals for any comments not addressed. Please note that your revised submission may need to be re-reviewed.  PLOS ONE values your contribution, and we look forward to receiving your revised manuscript. 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PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For more information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. In your revised cover letter, please address the following prompts: a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially sensitive information, data are owned by a third-party organization, etc.) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent. b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories. We will update your Data Availability statement on your behalf to reflect the information you provide. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Partly ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: The authors here study the influence of 5-HTT genotype variation on maternal sensitivity in parenting in a nonhuman primate model (Rhesus monkey) during the first three months of their infant’s lives. The authors hypothesized that, at an age when infants are still dependent on their mother to act as a secure base and to protect them, mothers possessing the s allele of the 5-HTT genotype will exhibit inappropriate parenting behaviours, such as premature maternal rejections of their immature, dependent infants. As a corollary, it is hypothesized that rhesus mothers with the s allele will be less likely to keep their infant in proximity, as measured by restraint and retrieving their infants’ attempts at exploration. Results showed that mothers homozygous for the s allele rejected their infants the most and restrained their infants the least, an indication that mothers with the s allele are more likely to neglect their infants’ psychological and physical needs. One of the strengths of the study is the number of individuals (N = 125 dyad mother – infant); n = 50 mothers were homozygous for the L allele, n = 58 mothers were heterozygotes, and n =14 mothers were homozygous for the s allele. Three subjects possessed rare 5-HTT variants (i.e., XL, XXL), and they were excluded from the analyses. This is a well writing and design research. The findings of this research add to the comprehension of the role of the genetic underpinnings individual differences in maternal sensitivity and suggest that maternal 5-HTT genotype plays a role in the quality of infant care. I only have minor comments. • It would be more informative to present the figures (graph) by showing both individual points and bars (to see the difference between individual). • By curiosity, in this primate model does the father also play a role in infant care? Reviewer #2: This study aims to understand the impact of 5-HTT genotype on maternal behaviors. The authors report that mothers homozygous for the s allele rejected their infants the most and restrained their infants the least, indications that mothers with the s allele are more likely to neglect their infants’ psychological and physical needs. The results are significant and advance our understanding of the etiology of variability in maternal warmth and care. In addition, the results suggests that maternal 5-HTT genotype should be examined in studies assessing genetic influences on variation in maternal sensitivity, and ultimately, mother-infant attachment quality Major: As the authors state in the discussion, results from human studies investigating the effect of the 5-HTT genotype on mother-infant interactions and attachment are mixed, with studies showing that mothers with the s allele are more likely to engage in insensitive parenting, while other studies show that mothers with an s allele exhibit more maternal sensitivity. In rodents it has also been shown that 5-HTT s-allele carriers have an increased risk to develop depression when exposed to ELS suggesting that carrying the s-allele does not inevitably have negative consequences. Rather, the increased sensitivity of s-allele carriers to a respective match or mismatch between the early and adult life environment may govern their adaptive or maladaptive responses to stress (PMID: 23319004). Overall, these discrepancies have led some to posit that 5-HTT as a plasticity gene, conveys risk for or protection from negative outcomes, depending on the environmental contexts. Therefore, the authors need to report on or control for maternal environmental stress and early life adversity in their analysis. Controlling for these factors may nuance their findings and further help us to resolve the issue whether 5-HTT as a plasticity gene governs adaptive or maladaptive maternal behaviors. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: Yes: Tamas Kozicz ******** [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0281935.r001
Revision 1
12 Jan 2023 Author Response Manuscript PONE-D-22-27260 Response to Reviewers January 10, 2023 Dear Dr. Kozicz, Thank you for giving us an opportunity to submit a revised draft of the manuscript, “Variation in the serotonin transporter genotype is associated with maternal restraint and rejection of infants: A nonhuman primate (Macaca mulatta) model” to PLOS ONE. We appreciate the time and effort that you and the reviewers dedicated to providing feedback on our manuscript. We have reviewed and incorporated reviewers’ suggestions. Those changes are highlighted within the manuscript. Please see below, in blue, a point-by-point response to the journal requirements and the reviewers’ comments and concerns. All page numbers refer to the revised manuscript file with the highlighted changes. Thank you, Dr. Elizabeth Wood Journal Requirements When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. Thank you for pointing this out. We have reviewed PLOS ONE’s style requirements and adjusted the manuscript accordingly. The modifications are highlighted in the revised version of the manuscript. 2. Thank you for stating the following in the Acknowledgments Section of your manuscript: “This work was supported by: R24OD010962 (JPC) and P51OD011157 (CNPRC base grant), as well as small mentoring grants from Brigham Young University.” We note that you have provided additional information within the Acknowledgements Section that is not currently declared in your Funding Statement. Please note that funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: “This work was supported by: R24OD010962 (JPC) and P51OD011157 (CNPRC base grant), as well as small mentoring grants from Brigham Young University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.” Please include your amended statements within your cover letter; we will change the online submission form on your behalf. We apologize for this error. We have removed the statement from the acknowledgements section of the manuscript. The funding statement should continue to read, “This work was supported by: R24OD010962 (JPC) and P51OD011157 (CNPRC base grant), as well as small mentoring grants from Brigham Young University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.” 3. We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For more information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. In your revised cover letter, please address the following prompts: a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially sensitive information, data are owned by a third-party organization, etc.) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent. b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories. We will update your Data Availability statement on your behalf to reflect the information you provide. To address this comment, we now provide a minimal anonymized dataset as a supporting information file (S1 File). Reviewers' comments: 1. Reviewer #1: The authors here study the influence of 5-HTT genotype variation on maternal sensitivity in parenting in a nonhuman primate model (Rhesus monkey) during the first three months of their infant’s lives. The authors hypothesized that, at an age when infants are still dependent on their mother to act as a secure base and to protect them, mothers possessing the s allele of the 5-HTT genotype will exhibit inappropriate parenting behaviours, such as premature maternal rejections of their immature, dependent infants. As a corollary, it is hypothesized that rhesus mothers with the s allele will be less likely to keep their infant in proximity, as measured by restraint and retrieving their infants’ attempts at exploration. Results showed that mothers homozygous for the s allele rejected their infants the most and restrained their infants the least, an indication that mothers with the s allele are more likely to neglect their infants’ psychological and physical needs. One of the strengths of the study is the number of individuals (N = 125 dyad mother – infant); n = 50 mothers were homozygous for the L allele, n = 58 mothers were heterozygotes, and n =14 mothers were homozygous for the s allele. Three subjects possessed rare 5-HTT variants (i.e., XL, XXL), and they were excluded from the analyses. This is a well writing and design research. The findings of this research add to the comprehension of the role of the genetic underpinnings individual differences in maternal sensitivity and suggest that maternal 5-HTT genotype plays a role in the quality of infant care. I only have minor comments. It would be more informative to present the figures (graph) by showing both individual points and bars (to see the difference between individual). We now provide individual data points in bar graphs in order to improve data visualization and increase transparency. These modifications are depicted in the supporting information of the manuscript as follows: By curiosity, in this primate model does the father also play a role in infant care? In this species, mothers are the primary caregivers, while fathers have a peripheral role. We have updated the discussion section of the manuscript to reflect this curiosity by including the following statement, “While fathers do not demonstrate direct infant care in this species (Lindburg, 1971), future studies focused on paternal contributions to infant development could assess the effect of fathers’ presence in the social group and 5-HTT genotype as mediators of offspring behavior early in life.” 2. Reviewer #2: This study aims to understand the impact of 5-HTT genotype on maternal behaviors. The authors report that mothers homozygous for the s allele rejected their infants the most and restrained their infants the least, indications that mothers with the s allele are more likely to neglect their infants’ psychological and physical needs. The results are significant and advance our understanding of the etiology of variability in maternal warmth and care. In addition, the results suggests that maternal 5-HTT genotype should be examined in studies assessing genetic influences on variation in maternal sensitivity, and ultimately, mother-infant attachment quality As the authors state in the discussion, results from human studies investigating the effect of the 5-HTT genotype on mother-infant interactions and attachment are mixed, with studies showing that mothers with the s allele are more likely to engage in insensitive parenting, while other studies show that mothers with an s allele exhibit more maternal sensitivity. In rodents it has also been shown that 5-HTT s-allele carriers have an increased risk to develop depression when exposed to ELS suggesting that carrying the s-allele does not inevitably have negative consequences. Rather, the increased sensitivity of s-allele carriers to a respective match or mismatch between the early and adult life environment may govern their adaptive or maladaptive responses to stress (PMID: 23319004). Overall, these discrepancies have led some to posit that 5-HTT as a plasticity gene, conveys risk for or protection from negative outcomes, depending on the environmental contexts. Therefore, the authors need to report on or control for maternal environmental stress and early life adversity in their analysis. Controlling for these factors may nuance their findings and further help us to resolve the issue whether 5-HTT as a plasticity gene governs adaptive or maladaptive maternal behaviors. We appreciate this comment and agree that early life conditions and 5-HTT genotypic effects are important to consider in tandem. To address this, in the Methods section we note the following, “With the exception of one subject that was reared in the nursery before introduction into the larger, outdoor social group into which her infant was born, the early life history of all of the subjects was identical, including being born into and reared in the large, outdoor corrals”. As well as, “As noted above, while the majority of mothers were born and reared as infants in the larger corrals, one mother (heterozygous for the 5-HTT genotype) was reared in the nursery. Preliminary analyses assessing the impact of including this subject showed no difference in the direction or significance of effects, so they were included in final models”. In the discussion, we also added, ”Our group has a long history of assessing the interaction between aberrant and normative early environments and the 5-HTT genotype (Bennett et al, 2002; Hunter et al, 2022; Wood et al 2021); however, in the present study all but one of the mothers came from a homogeneous population of females that experienced normative early life rearing conditions. These homogenous early experiences increased our ability to detect small effects, a strength of the study.” Attachments Attachment Submitted filename: 5HTT&InappropriateParenting_Response.docx https://doi.org/10.1371/journal.pone.0281935.r002
5 Feb 2023 Decision Letter - Tamas Kozicz, Editor Variation in the serotonin transporter genotype is associated with maternal restraint and rejection of infants: A nonhuman primate (Macaca mulatta) model PONE-D-22-27260R1 Dear Dr. Wood, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Tamas Kozicz Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: In this revised version of the MS all the concerns and point raised were addressed which have improved the manuscript. Reviewer #2: (No Response) ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: Yes: Tamas Kozicz M.D., Ph.D. ******** https://doi.org/10.1371/journal.pone.0281935.r003
Formally Accepted
14 Apr 2023 Acceptance Letter - Tamas Kozicz, Editor PONE-D-22-27260R1 Variation in the serotonin transporter genotype is associated with maternal restraint and rejection of infants: A nonhuman primate (Macaca mulatta) model Dear Dr. Wood: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Tamas Kozicz Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0281935.r004

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