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Du T, Xie Q, Ye J, Wang X, Qiu J, Yan Z, Zhang S, Zhao D, Lin J, Li B. Factors affecting male-to-female ratio at birth in frozen-thawed embryo transfer cycles: a large retrospective cohort study. Front Endocrinol (Lausanne) 2023; 14:1188433. [PMID: 37800141 PMCID: PMC10548202 DOI: 10.3389/fendo.2023.1188433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Accepted: 07/31/2023] [Indexed: 10/07/2023] Open
Abstract
Background ICSI (intracytoplasmic sperm injection) leads to a reduced male-to-female ratio at birth, whereas blastocyst transfer results in an increased male-to-female ratio. However, limited knowledge exists regarding the impact of these factors on the live birth rate for each gender. This study aimed to investigate the influence of patient characteristics and treatment parameters on the live birth rate for each gender, as well as the ultimate male-to-female ratio at birth in frozen-thawed embryo transfer (FET) cycles. Method This retrospective cohort study involved a total of 28,376 FET cycles and 9,217 subsequent deliveries, spanning from January 2003 to December 2015. The study consisted of two parts. First, logistic regression models were constructed to determine the factors influencing the male-to-female ratio among babies born after FET. Second, we aimed to investigate the mechanisms underlying this sex ratio imbalance by analyzing data from all transfer cycles. Generalized estimated equations were employed to assess the impact of risk factors on rates of male and female live births separately. Results ICSI resulted in a lower proportion of male offspring compared to in vitro fertilization (IVF) (50.1% vs. 53.7%, aOR: 0.87, 95% CI: 0.80-0.96). Conversely, blastocyst transfer yielded a higher proportion of male offspring than cleavage-stage embryo transfer (58.7% vs. 51.6%, aOR: 1.32, 95% CI: 1.17-1.48). Analysis of all cycles indicated that ICSI resulted in a reduced likelihood of male live birth in comparison to IVF (19.8% vs. 21.6%, aOR: 0.90, 95% CI: 0.83-0.97). However, the transfer of blastocysts rather than cleavage-stage embryos not only increased the chance of male live birth (26.9% vs. 20.2%, aOR: 1.70, 95% CI:1.56-1.85) but also facilitated female live birth (20.3% vs. 19.3%, aOR: 1.26, 95% CI: 1.15-1.39). Conclusion ICSI was associated with a reduction in the male-to-female sex ratio and a lower rate of male live births, while blastocyst transfer was associated with an increased male-to-female sex ratio at birth and a higher rate of male live births.
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Affiliation(s)
- Tong Du
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qin Xie
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jing Ye
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xindi Wang
- Department of Integrative Physiology and Biochemistry, University of Colorado at Boulder, Boulder, NV, United States
| | - Jiaxin Qiu
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zheng Yan
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Suqun Zhang
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Dong Zhao
- Department of Obstetrics and Gynaecology, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jiaying Lin
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Bin Li
- Department of Assisted Reproduction, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Pozdyshev DV, Kombarova NA, Muronetz VI. Biochemical Features of X or Y Chromosome-Bearing Spermatozoa for Sperm Sexing. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:655-666. [PMID: 37331711 DOI: 10.1134/s0006297923050085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/10/2023] [Accepted: 02/20/2023] [Indexed: 06/20/2023]
Abstract
This review presents information on biochemical features of spermatozoa bearing X or Y chromosome, enabling production of a sperm fraction with pre-defined sex chromosome. The almost only technology currently used for such separation (called sexing) is based on the fluorescence-activated cell sorting of sperm depending on DNA content. In addition to the applied aspects, this technology made it possible to analyze properties of the isolated populations of spermatozoa bearing X or Y chromosome. In recent years, existence of the differences between these populations at the transcriptome and proteome level have been reported in a number of studies. It is noteworthy that these differences are primarily related to the energy metabolism and flagellar structural proteins. New methods of sperm enrichment with X or Y chromosome cells are based on the differences in motility between the spermatozoa with different sex chromosomes. Sperm sexing is a part of the widespread protocol of artificial insemination of cows with cryopreserved semen, it allows to increase proportion of the offspring with the required sex. In addition, advances in the separation of X and Y spermatozoa may allow this approach to be applied in clinical practice to avoid sex-linked diseases.
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Affiliation(s)
- Denis V Pozdyshev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | - Nina A Kombarova
- Head Center for Reproduction of Agricultural Animals, 142143 Bykovo, Moscow Region, Russia
| | - Vladimir I Muronetz
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119991, Russia
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3
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Tarín JJ, García-Pérez MA, Cano A. It Is Premature to Use Postmortem Sperm for Reproductive Purposes: a Data-Driven Opinion. Reprod Sci 2022; 29:3387-3393. [PMID: 35146695 PMCID: PMC9734227 DOI: 10.1007/s43032-022-00874-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 01/31/2022] [Indexed: 12/14/2022]
Abstract
Postmortem sperm retrieval for reproductive purposes is an assisted reproduction procedure that offers women an opportunity to have a child using sperm retrieved from their deceased partners. The ethical issues of this procedure have been discussed in previous works. However, an assessment of the procedure using a scientific perspective is still lacking. Here, we aim to ascertain, using a biological standpoint, whether postmortem sperm should be rescued for reproductive purposes. Data suggest that it is premature to use postmortem sperm for reproductive purposes. This procedure should not be clinically applied until appropriate and comprehensive analyses have been completed. Such analyses should be focused not only on fertilization, embryo development, and pregnancy outcomes, but also on potential postmortem alterations of sperm DNA, RNAs, and proteins. In addition, genetic and epigenetic analyses of sperm, pre-implantation embryos, and newborns, as well as mental and physical health follow-up of the resulting offspring during a whole life cycle, using appropriate non-human mammalian models, are warranted.
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Affiliation(s)
- Juan J Tarín
- Department of Cellular Biology, Functional Biology and Physical Anthropology, Faculty of Biological Sciences, University of Valencia, Dr. Moliner 50, 46100, Burjassot, Valencia, Spain.
- Institute of Health Research INCLIVA, Valencia, Spain.
| | - Miguel A García-Pérez
- Institute of Health Research INCLIVA, Valencia, Spain
- Department of Genetics, Faculty of Biological Sciences, University of Valencia, Dr. Moliner 50, 46100, Burjassot, Valencia, Spain
| | - Antonio Cano
- Institute of Health Research INCLIVA, Valencia, Spain
- Service of Obstetrics and Gynecology, University Clinic Hospital, Valencia, Spain
- Department of Pediatrics, Obstetrics and Gynecology, Faculty of Medicine, University of Valencia, Av. Blasco Ibañez 17, 46010, Valencia, Spain
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4
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Teves ME, Roldan ERS. Sperm bauplan and function and underlying processes of sperm formation and selection. Physiol Rev 2022; 102:7-60. [PMID: 33880962 PMCID: PMC8812575 DOI: 10.1152/physrev.00009.2020] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 04/14/2021] [Accepted: 04/19/2021] [Indexed: 01/03/2023] Open
Abstract
The spermatozoon is a highly differentiated and polarized cell, with two main structures: the head, containing a haploid nucleus and the acrosomal exocytotic granule, and the flagellum, which generates energy and propels the cell; both structures are connected by the neck. The sperm's main aim is to participate in fertilization, thus activating development. Despite this common bauplan and function, there is an enormous diversity in structure and performance of sperm cells. For example, mammalian spermatozoa may exhibit several head patterns and overall sperm lengths ranging from ∼30 to 350 µm. Mechanisms of transport in the female tract, preparation for fertilization, and recognition of and interaction with the oocyte also show considerable variation. There has been much interest in understanding the origin of this diversity, both in evolutionary terms and in relation to mechanisms underlying sperm differentiation in the testis. Here, relationships between sperm bauplan and function are examined at two levels: first, by analyzing the selective forces that drive changes in sperm structure and physiology to understand the adaptive values of this variation and impact on male reproductive success and second, by examining cellular and molecular mechanisms of sperm formation in the testis that may explain how differentiation can give rise to such a wide array of sperm forms and functions.
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Affiliation(s)
- Maria Eugenia Teves
- Department of Obstetrics and Gynecology, Virginia Commonwealth University, Richmond, Virginia
| | - Eduardo R S Roldan
- Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain
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5
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Moradi M, Hajarian H, Karamishabankareh H, Soltani L, Soleymani B. Pre-treatment of ram semen extender with magnetic nanoparticles on freeze-thawed spermatozoa. Vet Med Sci 2021; 8:792-798. [PMID: 34914199 PMCID: PMC8959327 DOI: 10.1002/vms3.689] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Background Extensive use of different nanoparticles caused significant concerns about their biological safety. Objective This study aimed to evaluate the effects of cryopreservation on ram semen after adding magnetic nanoparticles (MNPs) to separate X and Y chromosome‐bearing spermatozoa. Methods The experimental ram sperms in this research included treated spermatozoa (50 μg/ml MNPs) and non‐treated spermatozoa. DNA damage of spermatozoa was examined using an acridine orange (AO) assay. Sperm viability, membrane functionality, abnormality and malondialdehyde (MDA) level were also measured. Results Results indicated that the pre‐treatment of ram semen extender with MNPs did not significantly affect the semen parameters such as viability, membrane functionality, abnormality, as well as lipid peroxidation (LPO) levels and DNA integrity in comparison with the control group (p < 0.05). Conclusions These observations suggest that pre‐treatment of ram semen extender with MNPs after semen sexing did not have adverse effects on different semen parameters after cryopreservation. In the current study, we evaluated the effects of cryopreservation on ram semen after adding magnetic nanoparticles (MNPs), then after thawing some semen parameters were evaluated.
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Affiliation(s)
- Maryam Moradi
- Faculty of Agricultural and Engineering Science, Department of Animal Science, Razi University, Kermanshah, Iran
| | - Hadi Hajarian
- Faculty of Agricultural and Engineering Science, Department of Animal Science, Razi University, Kermanshah, Iran
| | - Hamed Karamishabankareh
- Faculty of Agricultural and Engineering Science, Department of Animal Science, Razi University, Kermanshah, Iran
| | - Leila Soltani
- Faculty of Agricultural and Engineering Science, Department of Animal Science, Razi University, Kermanshah, Iran
| | - Bijan Soleymani
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Science, Kermanshah, Iran
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6
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Hu C, Shi J, Chi Y, Yang J, Cui Q. Y/X-Chromosome-Bearing Sperm Shows Elevated Ratio in the Left but Not the Right Testes in Healthy Mice. Life (Basel) 2021; 11:life11111219. [PMID: 34833095 PMCID: PMC8621333 DOI: 10.3390/life11111219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 10/30/2021] [Accepted: 10/31/2021] [Indexed: 11/16/2022] Open
Abstract
The sex chromosomes play central roles in determining the sex of almost all of the multicellular organisms. It is well known that meiosis in mammalian spermatogenesis produces ~50% Y- and ~50% X-chromosome-bearing sperm, a 1:1 ratio. Here we first reveal that the X-chromosome-encoded miRNAs show lower expression levels in the left testis than in the right testis in healthy mice using bioinformatics modeling of miRNA-sequencing data, suggesting that the Y:X ratio could be unbalanced between the left testis and the right testis. We further reveal that the Y:X ratio is significantly elevated in the left testis but balanced in the right testis using flow cytometry. This study represents the first time the biased Y:X ratio in the left testis but not in the right testis is revealed.
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Affiliation(s)
- Chengqing Hu
- Center for Noncoding RNA Medicine, Department of Physiology and Pathophysiology, Department of Biomedical Informatics, MOE Key Laboratory of Cardiovascular Sciences, School of Basic Medical Sciences, Peking University, 38 Xueyuan Rd, Beijing 100191, China; (C.H.); (J.S.)
| | - Jiangcheng Shi
- Center for Noncoding RNA Medicine, Department of Physiology and Pathophysiology, Department of Biomedical Informatics, MOE Key Laboratory of Cardiovascular Sciences, School of Basic Medical Sciences, Peking University, 38 Xueyuan Rd, Beijing 100191, China; (C.H.); (J.S.)
| | - Yujing Chi
- Department of Central Laboratory & Institute of Clinical Molecular Biology, Peking University People’s Hospital, Beijing 100044, China;
| | - Jichun Yang
- Center for Noncoding RNA Medicine, Department of Physiology and Pathophysiology, Department of Biomedical Informatics, MOE Key Laboratory of Cardiovascular Sciences, School of Basic Medical Sciences, Peking University, 38 Xueyuan Rd, Beijing 100191, China; (C.H.); (J.S.)
- Correspondence: (J.Y.); (Q.C.); Tel.: +86-010-82801403 (J.Y.); +86-010-82801001 (Q.C.)
| | - Qinghua Cui
- Center for Noncoding RNA Medicine, Department of Physiology and Pathophysiology, Department of Biomedical Informatics, MOE Key Laboratory of Cardiovascular Sciences, School of Basic Medical Sciences, Peking University, 38 Xueyuan Rd, Beijing 100191, China; (C.H.); (J.S.)
- Correspondence: (J.Y.); (Q.C.); Tel.: +86-010-82801403 (J.Y.); +86-010-82801001 (Q.C.)
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7
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Quelhas J, Santiago J, Matos B, Rocha A, Lopes G, Fardilha M. Bovine semen sexing: Sperm membrane proteomics as candidates for immunological selection of X- and Y-chromosome-bearing sperm. Vet Med Sci 2021; 7:1633-1641. [PMID: 34037311 PMCID: PMC8464243 DOI: 10.1002/vms3.540] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 04/14/2021] [Accepted: 05/03/2021] [Indexed: 01/25/2023] Open
Abstract
The use of sexed semen in dairy and beef farms ensures the production of animals of the desired sex, resulting in a reduction of costs and an improvement of environmental sustainability. Several methods have been developed over the years, but most of them were abandoned due to their limited efficacy. Currently, the only commercially available method for the separation of X- and Y-chromosome-bearing sperm is fluorescence-activated cell sorting. However, this technique is expensive and has limited usefulness for the industry, considering that it cannot produce doses of sexed semen with the desired number of sperm for artificial insemination. Immunological methods have emerged as an attractive alternative to flow cytometry and proteomic knowledge of X- and Y-sperm could be useful to the development of a new method. In this review, we identify the main applications of sexed semen, describe the existing methods and highlight future research opportunities in the field. We consider that immunological methods, based on sperm cell's surface proteins differentially expressed between X- and Y-sperm, could be an interesting and promising approach to semen sexing.
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Affiliation(s)
- Joana Quelhas
- Bovine Semen Collection and Storage Centre of Lusogenes, Aveiro, Portugal.,Laboratory of Signal Transduction, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal.,Department of Veterinary Clinics, Institute of Biomedical Sciences Abel Salazar-University of Porto, Porto, Portugal
| | - Joana Santiago
- Laboratory of Signal Transduction, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - Bárbara Matos
- Laboratory of Signal Transduction, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
| | - António Rocha
- Department of Imuno-Physiology and Pharmacology, Institute of Biomedical Sciences Abel Salazar- University of Porto, Porto, Portugal
| | - Graça Lopes
- Department of Veterinary Clinics, Institute of Biomedical Sciences Abel Salazar-University of Porto, Porto, Portugal
| | - Margarida Fardilha
- Laboratory of Signal Transduction, Department of Medical Sciences, Institute of Biomedicine - iBiMED, University of Aveiro, Aveiro, Portugal
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8
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Vaamonde D, Hackney AC, Garcia Manso JM, Arriaza Ardiles E, Vaquero M. Birth sex ratio in the offspring of professional male soccer players: influence of exercise training load. Hum Reprod 2021; 35:2613-2618. [PMID: 33006607 DOI: 10.1093/humrep/deaa225] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 07/26/2020] [Indexed: 11/14/2022] Open
Abstract
STUDY QUESTION Can the exercise training load of elite male athletes influence the sex ratio of their offspring? SUMMARY ANSWER This is the first study assessing the influence of exercise training load on the offspring sex ratio of children from male professional athletes, observing a bias toward more females being born as a result of both high-intensity and high-volume loads, with intensity having the greatest effect. WHAT IS KNOWN ALREADY There is a relatively constant population sex ratio of males to females among various species; however, certain events and circumstances may alter this population sex ratio favoring one sex over the other. STUDY DESIGN, SIZE, DURATION Observational, descriptive cross-sectional study with a duration of 3 months. PARTICIPANTS/MATERIALS, SETTING, METHODS Seventy-five male professional soccer players from First Division soccer teams. Offspring variables were sex of the offspring, number of children and order of birth. Exercise training variables were volume and intensity. MAIN RESULTS AND THE ROLE OF CHANCE Total offspring was 122 children (52 males (42.6%), 70 females (57.4%)). Analysis revealed that increase in either the volume (P < 0.001) or intensity (P < 0.001) of training by the players shifted the birth offspring ratio more toward females. Within the sample of females born, more births (i.e. number) were observed as a consequence of training at the highest intensity (45 out of 70; P < 0.001), no such pattern occurred within males (P > 0.05). When female versus male births were compared within each intensity, only the high-intensity comparison was significant (45 (75%) females vs 15 (25%) males, P < 0.001). LIMITATIONS, REASONS FOR CAUTION While this is the first study assessing differences in the sex ratio of the offspring of male athletes (i.e. soccer players), we acknowledge there are limitations and confounders within our approach; e.g. small sample size, ethnic background and variations in the timing of intercourse relative to ovulation as well as in sex hormone levels. As such, we propose that future research is needed to confirm or refute our findings. It is recommended that such work expand on the measurements obtained and conduct direct assessment of sperm characteristics. WIDER IMPLICATIONS OF THE FINDINGS The findings of the study support the fact that different stressors on the body may alter the sex of the offspring. While in the present study the stressor is the excessive training load of soccer players, other events may lead to similar results. The bias in offspring sex ratio may have important implications for demography and population dynamics, as well as genetic trait inheritance. STUDY FUNDING/COMPETING INTEREST(S) There is no funding nor competing interests. TRIAL REGISTRATION NUMBER N/A.
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Affiliation(s)
- D Vaamonde
- Department of Morphological Sciences, School of Medicine and Nursing, Universidad de Cordoba, Cordoba, Spain.,International Network on Physical Exercise and Fertility (INPEF), Córdoba, Spain
| | - A C Hackney
- International Network on Physical Exercise and Fertility (INPEF), Córdoba, Spain.,Department of Exercise & Sport Science, University of North Carolina, Chapel Hill, NC, USA
| | - J M Garcia Manso
- International Network on Physical Exercise and Fertility (INPEF), Córdoba, Spain.,Department of Physical Education, School of Physical Activity and Sports, Universidad de Las Palmas de Gran Canaria, Las Palmas, Canary Islands, Spain
| | - E Arriaza Ardiles
- Center of Advanced Studies, Universidad de Playa Ancha, Valparaiso, Chile
| | - M Vaquero
- Department of Public Health, School of Medicine and Nursing, Universidad de Córdoba, Córdoba, Spain.,IMIBIC Clinical and Epidemiological Research in Primary Care, Córdoba, Spain
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9
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Laxmivandana R, Patole C, Sharma TR, Sharma KK, Naskar S. Differential proteins associated with plasma membrane in X- and/or Y-chromosome bearing spermatozoa in indicus cattle. Reprod Domest Anim 2021; 56:928-935. [PMID: 33829570 DOI: 10.1111/rda.13936] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 04/05/2021] [Indexed: 11/29/2022]
Abstract
The differential proteins associated with plasma membrane of spermatozoa are less known, identification of which shall help overcome limitations of currently used methods of sperm sexing, considered as a high priority for livestock sector of many countries. This study has reported plasma membrane proteomics of unsorted spermatozoa and differential expression of plasma membrane-associated proteins between X- and Y-chromosome bearing spermatozoa of indicus cattle (Bos indicus). Isolation of plasma membrane fraction using percoll gradient, relatively a rapid method, from bovine spermatozoa has been reported to enrich isolation of plasma membrane proteins. Significant enrichment for plasma membrane-associated proteins was observed in plasma membrane fraction (p < .05) as compared to the total cell lysate using LC-MS/MS. Furthermore, these experiments were conducted in flow cytometry sorted, sexed-semen samples. Thirteen proteins were identified as differentially abundant between X- and Y-sorted spermatozoa. Among these, two proteins were downregulated in Y-sorted spermatozoa compared to the X-sorted spermatozoa (p < .05), while four and seven proteins could be noted in X- and Y-sorted spermatozoa, respectively. Proteins that are presumed to support sperm capacitation and sperm migration velocity were found to be abundant in Y-sorted spermatozoa while those associated with structural molecule activity were identified as abundant in X-sorted spermatozoa in the present study. Our study provides better insight into the plasma membrane proteomics of spermatozoa of indicus cattle and furnishes data that might aid in design and development of alternate and open technology for sex-sorting of semen.
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Affiliation(s)
| | | | - Tilak Raj Sharma
- ICAR-Indian Institute of Agricultural Biotechnology, Ranchi, India
| | | | - Soumen Naskar
- ICAR-Indian Institute of Agricultural Biotechnology, Ranchi, India
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10
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Soleymani B, Mansouri K, Rastegari-Pouyani M, Parvaneh S, Khademi F, Sharifi Tabar M, Mostafaie A. Production of monoclonal antibody against recombinant bovine sex-determining region Y (SRY) and their preferential binding to Y chromosome-bearing sperm. Reprod Domest Anim 2021; 56:270-277. [PMID: 32920908 DOI: 10.1111/rda.13821] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 09/05/2020] [Indexed: 11/28/2022]
Abstract
Separation of X and Y chromosome-bearing sperm is an appropriate method for the selection of desired sex of offspring to increase the profit in livestock industries. The purpose of this study was the production of a monoclonal antibody against recombinant bovine sex-determining region Y protein for separation Y sperm. The hybridoma cells from splenocytes of immunized female's balb/C mice and Sp2/0 cells were made. The binding affinity of our monoclonal antibody (mAbSRY2) was compared with mouse monoclonal SRY-15. The Western blot method indicated that mAbSRY2 successfully detected the rbSRY protein. The specificity and sensitivity of mAbSRY2 is comparable to SRY-15 commercially ones. The SRY gene in 100% of bull semen contains the Y chromosome that had the strongest binding affinity to mAbSRY2 was synthesized. In other words, the binding affinity of semen contains the X sperms near the negative control. In general, this immunological method can help to separate X from Y sperms. However, the mAbSRY2 is bind to Y-bearing sexed sperm, but in the future; the sexed sperms need to apply in farms.
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Affiliation(s)
- Bijan Soleymani
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Kamran Mansouri
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Mohsen Rastegari-Pouyani
- Student Research Committee, Department of Immunology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Shahram Parvaneh
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Fatemeh Khademi
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Mehdi Sharifi Tabar
- School of Life and Environmental Science, University of Sydney, Sydney, NSW, Australia
| | - Ali Mostafaie
- Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran
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11
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Navarro-Costa PA, Molaro A, Misra CS, Meiklejohn CD, Ellis PJ. Sex and suicide: The curious case of Toll-like receptors. PLoS Biol 2020; 18:e3000663. [PMID: 32203540 PMCID: PMC7117759 DOI: 10.1371/journal.pbio.3000663] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 04/02/2020] [Indexed: 12/21/2022] Open
Abstract
During in vitro fertilisation (IVF), pharmacological activation of the murine X chromosome-encoded receptor proteins Toll-like receptor (TLR) 7 and TLR8 reportedly results in male-biased litters by selectively disrupting the motility of X-bearing sperm cells. Thus-in the context of agonist treatment during IVF-these receptors act as 'suicidal' segregation distorters that impair their own transmission to the next generation. Such behaviour would, from an evolutionary perspective, be strongly selected against if present during natural fertilisation. Consequently, TLR7/8 biology in vivo must differ significantly from this in vitro situation to allow these genes to persist in the genome. Here, we use our current understanding of male germ cell biology and TLR function as a starting point to explore the mechanistic and evolutionary aspects of this apparent paradox.
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Affiliation(s)
- Paulo A. Navarro-Costa
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- Instituto de Saúde Ambiental, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Antoine Molaro
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Chandra S. Misra
- Instituto Gulbenkian de Ciência, Oeiras, Portugal
- Instituto de Tecnologia Química e Biológica, Oeiras, Portugal
| | - Colin D. Meiklejohn
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Peter J. Ellis
- School of Biosciences, University of Kent, Canterbury, United Kingdom
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Rathje CC, Johnson EEP, Drage D, Patinioti C, Silvestri G, Affara NA, Ialy-Radio C, Cocquet J, Skinner BM, Ellis PJI. Differential Sperm Motility Mediates the Sex Ratio Drive Shaping Mouse Sex Chromosome Evolution. Curr Biol 2019; 29:3692-3698.e4. [PMID: 31630954 PMCID: PMC6839398 DOI: 10.1016/j.cub.2019.09.031] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 08/02/2019] [Accepted: 09/12/2019] [Indexed: 01/20/2023]
Abstract
The mouse sex chromosomes exhibit an extraordinary level of copy number amplification of postmeiotically expressed genes [1, 2], driven by an “arms race” (genomic conflict) between the X and Y chromosomes over the control of offspring sex ratio. The sex-linked ampliconic transcriptional regulators Slx and Sly [3, 4, 5, 6, 7] have opposing effects on global transcription levels of the sex chromosomes in haploid spermatids via regulation of postmeiotic sex chromatin (PMSC) [8, 9, 10, 11] and opposing effects on offspring sex ratio. Partial deletions of the Y chromosome (Yq) that reduce Sly copy number lead to global overexpression of sex-linked genes in spermatids and either a distorted sex ratio in favor of females (smaller deletions) or sterility (larger deletions) [12, 13, 14, 15, 16]. Despite a large body of work studying the role of the sex chromosomes in regulating spermatogenesis (recent reviews [17, 18, 19, 20]), most studies do not address differential fertility effects on X- and Y-bearing cells. Hence, in this study, we concentrate on identifying physiological differences between X- and Y-bearing sperm from Yq-deleted males that affect their relative fertilizing ability and consequently lead to sex ratio skewing. We show that X- and Y-bearing sperm in these males have differential motility and morphology but are equally able to penetrate the cumulus and fertilize the egg once at the site of fertilization. The altered motility is thus deduced to be the proximate cause of the skew. This represents the first demonstration of a specific difference in sperm function associated with sex ratio skewing. The sex ratio skew in the offspring of Yq-deleted male mice is abolished by IVF In Yqdel males, Y sperm are more severely morphologically distorted than X sperm Similarly, Y sperm in these males have relatively impaired motility This motility difference explains the sex ratio skew in offspring of these males
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Affiliation(s)
| | | | - Deborah Drage
- University Biomedical Services, University of Cambridge, Cambridge CB2 2SP, UK
| | | | | | - Nabeel Ahmed Affara
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Côme Ialy-Radio
- Department of Development, Reproduction and Cancer, INSERM, U1016, Institut Cochin, Paris, France; CNRS, UMR8104, Paris, France; Sorbonne Paris Cité, Faculté de Médecine, Université Paris Descartes, Paris, France
| | - Julie Cocquet
- Department of Development, Reproduction and Cancer, INSERM, U1016, Institut Cochin, Paris, France; CNRS, UMR8104, Paris, France; Sorbonne Paris Cité, Faculté de Médecine, Université Paris Descartes, Paris, France
| | - Benjamin Matthew Skinner
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK; School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK
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Casser E, Israel S, Schlatt S, Nordhoff V, Boiani M. Retrospective analysis: reproducibility of interblastomere differences of mRNA expression in 2-cell stage mouse embryos is remarkably poor due to combinatorial mechanisms of blastomere diversification. Mol Hum Reprod 2019; 24:388-400. [PMID: 29746690 DOI: 10.1093/molehr/gay021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 05/05/2018] [Indexed: 01/13/2023] Open
Abstract
STUDY QUESTION What is the prevalence, reproducibility and biological significance of transcriptomic differences between sister blastomeres of the mouse 2-cell embryo? SUMMARY ANSWER Sister 2-cell stage blastomeres are distinguishable from each other by mRNA analysis, attesting to the fact that differentiation starts mostly early in the mouse embryo; however, the interblastomere differences are poorly reproducible and invoke the combinatorial effects of known and new mechanisms of blastomere diversification. WHAT IS KNOWN ALREADY Transcriptomic datasets for single blastomeres in mice have been available for years but have never been systematically analysed together, although such an analysis may shed light onto some unclarified topics of early mammalian development. Two unknowns that remain are at which stage embryonic blastomeres start to diversify from each other and what is the molecular origin of that difference. At the earliest postzygotic stage, the 2-cell stage, opinions differ regarding the answer to these questions; one group claims that the first zygotic division yields two equal blastomeres capable of forming a full organism (totipotency) and another group claims evidence for interblastomere differences reminiscent of the prepatterning found in embryos of lower taxa. Regarding the molecular origin of interblastomere differences, there are four prevalent models which invoke (1) oocyte anisotropy, (2) sperm entry point, (3) partition errors of the transcript pool and (4) asynchronous embryonic genome activation in the two blastomeres. STUDY DESIGN, SIZE, DURATION Seven transcriptomic studies published between 2011 and 2017 were eligible for retrospective analysis, since both blastomeres of the mouse 2-cell embryo had been analysed individually regarding the original pair associations and since the datasets were made available in public repositories. Five of these studies, encompassing a total of 43 pairs of sister blastomeres, were selected for further analyses based on high interblastomere correlations of mRNA levels. A double cut-off was used to select mRNAs that had robust interblastomere differences both within and between embryos (hits). The hits of each study were compared and contrasted with the hits of the other studies using Venn diagrams. The hits shared by at least four of five studies were analysed further by bioinformatics. PARTICIPANTS/MATERIALS, SETTING, METHODS PubMed was systematically examined for mRNA expression profiles of single 2-cell stage blastomeres in addition to publicly available microarray datasets (GEO, ArrayExpress). Based on the original normalizations, data from seven studies were screened for pairwise sample correlation at the gene level (Spearman), and the top five datasets with the highest correlation were subjected to hierarchical cluster analysis. Interblastomere differences of gene expression were expressed as a ratio of the higher to the lower mRNA level for each pair of blastomeres. A double cut-off was used to make the call of interblastomere difference, accepting genes with mRNA ratios above 2 when observed in at least 50% of the pairs, and discarding the other genes. The proportion of interblastomere differences common to at least four of the five datasets was calculated. Finally, the corresponding gene, pathway and enrichment analyses were performed utilizing PANTHER and GORILLA platforms. MAIN RESULTS AND THE ROLE OF CHANCE An average of 17% of genes within the datasets are differently expressed between sister blastomeres, a proportion which falls to 1% when considering the differences that are common to at least four of the five studies. Housekeeping mRNAs were not included in the 17% and 1% gene lists, suggesting that the interblastomere differences do not occur simply by chance. The 1% of shared interblastomere differences comprise 100 genes, of which 35 are consistent with at least one of the four prevalent models of sister blastomere diversification. Bioinformatics analysis of the remaining 65 genes that are not consistent with the four models suggests that at least one more mechanism is at play, potentially related to the endomembrane system. Although there are many dimensions to the issue of reproducibility (biological, experimental, analytical), we consider that the sister blastomeres are poised to escape high interblastomere correlations of mRNA levels, because at least five sources of diversity superimpose on each other, accounting for at least 25 = 32 different states. As a result, interblastomere mRNA differences of a given 2-cell embryo are necessarily difficult to reproduce in another 2-cell embryo. LARGE SCALE DATA Data were as provided by the original studies (GSE21688, GSE22182, GSE27396, GSE45719, GSE57249, E-MTAB-3321, GSE94050). LIMITATIONS, REASONS FOR CAUTION The original studies present similarities (e.g. fertilization in vivo after ovarian stimulation) as well as differences (e.g. mouse strains, method and timing of blastomere separation). We identified robust mRNA differences between the sister blastomeres, but these differences are underestimated because our double cut-off method works with thresholds and affords more protection against false positives than false negatives. Regarding the false negatives, transcriptome analysis may have captured only part of the interblastomere differences due to: (1) the 2-fold cut-off not being sensitive enough to detect the remaining part of the interblastomere differences, (2) the detection limit of the transcriptomic methods not being sufficient, or (3) interblastomere differences being oblivious to transcriptomic identification because transcriptional changes are oscillatory or because differences are mediated non-transcriptionally or post-transcriptionally. Regarding the false positives, it seems unlikely that a difference was found just by chance for the same group of transcripts due to the same technical error, given that different laboratories produced the data. WIDER IMPLICATIONS OF THE FINDINGS It is clear that the sister blastomeres are distinguishable from each other by mRNA analysis even at the 2-cell stage; however, efforts to identify large stable patterns may be in vain. This elicits thoughts about the wisdom of adding new transcriptomic datasets to the ones that already exist; if all transcriptomic datasets produced so far show a reproducibility of 1%, then any future study would probably face the same issue again. Possibly, a solid identification of the 'large stable pattern that should be there but was not found' requires an even larger dataset than the sum of the seven datasets considered here. Conversely, small stable patterns may be easier to identify, but their biological relevance is less obvious. Alternatively, interblastomere differences may not be mediated by nucleic acids but by other cellular components. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by the Deutsche Forschungsgemeinschaft (grant DFG BO 2540-4-3 to M.B. and grant NO 413/3-3 to V.N.). The authors declare that they have no competing financial interests.
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Affiliation(s)
- E Casser
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, Muenster, Germany
| | - S Israel
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, Muenster, Germany
| | - S Schlatt
- University Hospital Muenster, Centre of Reproductive Medicine and Andrology (CeRA), Albert Schweitzer-Campus 1, Building D11, Muenster, Germany
| | - V Nordhoff
- University Hospital Muenster, Centre of Reproductive Medicine and Andrology (CeRA), Albert Schweitzer-Campus 1, Building D11, Muenster, Germany
| | - M Boiani
- Max Planck Institute for Molecular Biomedicine, Roentgenstrasse 20, Muenster, Germany
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Holt W, Fazeli A. Sperm selection in the female mammalian reproductive tract. Focus on the oviduct: Hypotheses, mechanisms, and new opportunities. Theriogenology 2016; 85:105-12. [DOI: 10.1016/j.theriogenology.2015.07.019] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 07/13/2015] [Accepted: 07/16/2015] [Indexed: 12/19/2022]
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Holt WV, Fazeli A. Do sperm possess a molecular passport? Mechanistic insights into sperm selection in the female reproductive tract. ACTA ACUST UNITED AC 2015; 21:491-501. [DOI: 10.1093/molehr/gav012] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 03/04/2015] [Indexed: 12/26/2022]
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Tarín JJ, García-Pérez MA, Cano A. Assisted reproductive technology results: Why are live-birth percentages so low? Mol Reprod Dev 2014; 81:568-83. [DOI: 10.1002/mrd.22340] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 05/03/2014] [Indexed: 01/30/2023]
Affiliation(s)
- Juan J. Tarín
- Department of Functional Biology and Physical Anthropology; Faculty of Biological Sciences; University of Valencia; Burjassot Valencia Spain
| | - Miguel A. García-Pérez
- Research Unit-INCLIVA; Hospital Clínico de Valencia; Burjassot Valencia Spain
- Department of Genetics; Faculty of Biological Sciences; University of Valencia; Burjassot Valencia Spain
| | - Antonio Cano
- Department of Pediatrics; Obstetrics and Gynecology; Faculty of Medicine; University of Valencia; Valencia Spain
- Service of Obstetrics and Gynecology; University Hospital Dr. Peset; Valencia Spain
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Tarín JJ, García-Pérez MA, Hermenegildo C, Cano A. Changes in sex ratio from fertilization to birth in assisted-reproductive-treatment cycles. Reprod Biol Endocrinol 2014; 12:56. [PMID: 24957129 PMCID: PMC4079184 DOI: 10.1186/1477-7827-12-56] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 06/10/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In Western gender-neutral countries, the sex ratio at birth is estimated to be approximately 1.06. This ratio is lower than the estimated sex ratio at fertilization which ranges from 1.07 to 1.70 depending on the figures of sex ratio at birth and differential embryo/fetal mortality rates taken into account to perform these estimations. Likewise, little is known about the sex ratio at implantation in natural and assisted-reproduction-treatment (ART) cycles. In this bioessay, we aim to estimate the sex ratio at fertilization and implantation using data from embryos generated by standard in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) in preimplantation genetic diagnosis cycles. Thereafter, we compare sex ratios at implantation and birth in cleavage- and blastocyst-stage-transfer cycles to propose molecular mechanisms accounting for differences in post-implantation male and female mortality and thereby variations in sex ratios at birth in ART cycles. METHODS A literature review based on publications up to December 2013 identified by PubMed database searches. RESULTS Sex ratio at both fertilization and implantation is estimated to be between 1.29 and 1.50 in IVF cycles and 1.07 in ICSI cycles. Compared with the estimated sex ratio at implantation, sex ratio at birth is lower in IVF cycles (1.03 after cleavage-stage transfer and 1.25 after blastocyst-stage transfer) but similar and close to unity in ICSI cycles (0.95 after cleavage-stage transfer and 1.04 after blastocyst-stage transfer). CONCLUSIONS In-vitro-culture-induced precocious X-chromosome inactivation together with ICSI-induced decrease in number of trophectoderm cells in female blastocysts may account for preferential female mortality at early post-implantation stages and thereby variations in sex ratios at birth in ART cycles.
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Affiliation(s)
- Juan J Tarín
- Department of Functional Biology and Physical Anthropology, Faculty of Biological Sciences, University of Valencia, Burjassot, Valencia 46100, Spain
| | - Miguel A García-Pérez
- Department of Genetics, Faculty of Biological Sciences, University of Valencia, Burjassot, Valencia 46100; and Research Unit-INCLIVA, Hospital Clínico de Valencia, Valencia 46010, Spain
| | - Carlos Hermenegildo
- Department of Physiology, Faculty of Medicine, University of Valencia, Valencia 46010; and Research Unit-INCLIVA, Hospital Clínico de Valencia, Valencia 46010, Spain
| | - Antonio Cano
- Department of Pediatrics, Obstetrics and Gynecology, Faculty of Medicine, University of Valencia, Valencia 46010; and Service of Obstetrics and Gynecology, University Hospital Dr. Peset, Valencia 46017, Spain
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Tentative identification of sex-specific antibodies and their application for screening bovine sperm proteins for sex-specificity. Mol Biol Rep 2013; 41:217-23. [DOI: 10.1007/s11033-013-2854-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 10/30/2013] [Indexed: 10/26/2022]
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Cocquet J, Ellis PJI, Mahadevaiah SK, Affara NA, Vaiman D, Burgoyne PS. A genetic basis for a postmeiotic X versus Y chromosome intragenomic conflict in the mouse. PLoS Genet 2012; 8:e1002900. [PMID: 23028340 PMCID: PMC3441658 DOI: 10.1371/journal.pgen.1002900] [Citation(s) in RCA: 136] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 07/01/2012] [Indexed: 11/27/2022] Open
Abstract
Intragenomic conflicts arise when a genetic element favours its own transmission to the detriment of others. Conflicts over sex chromosome transmission are expected to have influenced genome structure, gene regulation, and speciation. In the mouse, the existence of an intragenomic conflict between X- and Y-linked multicopy genes has long been suggested but never demonstrated. The Y-encoded multicopy gene Sly has been shown to have a predominant role in the epigenetic repression of post meiotic sex chromatin (PMSC) and, as such, represses X and Y genes, among which are its X-linked homologs Slx and Slxl1. Here, we produced mice that are deficient for both Sly and Slx/Slxl1 and observed that Slx/Slxl1 has an opposite role to that of Sly, in that it stimulates XY gene expression in spermatids. Slx/Slxl1 deficiency rescues the sperm differentiation defects and near sterility caused by Sly deficiency and vice versa. Slx/Slxl1 deficiency also causes a sex ratio distortion towards the production of male offspring that is corrected by Sly deficiency. All in all, our data show that Slx/Slxl1 and Sly have antagonistic effects during sperm differentiation and are involved in a postmeiotic intragenomic conflict that causes segregation distortion and male sterility. This is undoubtedly what drove the massive gene amplification on the mouse X and Y chromosomes. It may also be at the basis of cases of F1 male hybrid sterility where the balance between Slx/Slxl1 and Sly copy number, and therefore expression, is disrupted. To the best of our knowledge, our work is the first demonstration of a competition occurring between X and Y related genes in mammals. It also provides a biological basis for the concept that intragenomic conflict is an important evolutionary force which impacts on gene expression, genome structure, and speciation. Both copies of a gene have normally an equal chance of being inherited; however, some genes can act “selfishly” to be transmitted to >50% of offspring: a phenomenon known as transmission distortion. Distorting genes on the X or Y chromosome leads to an excess of female/male offspring respectively. This then sets up a “genomic conflict” (arms race) between the sex chromosomes that can radically affect their gene content. Male mice that have lost part of their Y produce >50% female offspring and show over-activation of multiple genes on the X, providing strong circumstantial evidence for distortion. Here, we demonstrate the existence of a genomic conflict regulated by the genes Slx/Slxl1 and Sly, present in ∼50 to 100 copies on the X and Y chromosomes respectively. SLX/SLXL1 and SLY proteins have antagonistic effects on sex chromosome expression in developing sperm and skew the offspring sex-ratio in favor of females/males. Interestingly, while deficiency of either gene alone leads to severe fertility problems, fertility is improved when both genes are deficient. We believe that the conflict in which Slx/Slxl1 and Sly are involved led to the amplification of X and Y genes and may have played an important role in mouse speciation.
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