1
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Pazhayam NM, Frazier LK, Sekelsky J. Centromere-proximal suppression of meiotic crossovers in Drosophila is robust to changes in centromere number, repetitive DNA content, and centromere-clustering. Genetics 2024; 226:iyad216. [PMID: 38150397 PMCID: PMC10917511 DOI: 10.1093/genetics/iyad216] [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: 10/16/2023] [Revised: 12/05/2023] [Accepted: 12/10/2023] [Indexed: 12/29/2023] Open
Abstract
Accurate segregation of homologous chromosomes during meiosis depends on both the presence and the regulated placement of crossovers (COs). The centromere effect, or CO exclusion in pericentromeric regions of the chromosome, is a meiotic CO patterning phenomenon that helps prevent nondisjunction, thereby protecting against chromosomal disorders and other meiotic defects. Despite being identified nearly a century ago, the mechanisms behind this fundamental cellular process remain unknown, with most studies of the Drosophila centromere effect focusing on local influences of the centromere and pericentric heterochromatin. In this study, we sought to investigate whether dosage changes in centromere number and repetitive DNA content affect the strength of the centromere effect, using phenotypic recombination mapping. Additionally, we studied the effects of repetitive DNA function on centromere effect strength using satellite DNA-binding protein mutants displaying defective centromere-clustering in meiotic nuclei. Despite what previous studies suggest, our results show that the Drosophila centromere effect is robust to changes in centromere number, repetitive DNA content, as well as repetitive DNA function. Our study suggests that the centromere effect is unlikely to be spatially controlled, providing novel insight into the mechanisms behind the Drosophila centromere effect.
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Affiliation(s)
- Nila M Pazhayam
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Leah K Frazier
- SURE-REU Program in Biological Mechanisms, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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2
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Ariad D, Madjunkova S, Madjunkov M, Chen S, Abramov R, Librach C, McCoy RC. Aberrant landscapes of maternal meiotic crossovers contribute to aneuploidies in human embryos. Genome Res 2024; 34:70-84. [PMID: 38071472 PMCID: PMC10903951 DOI: 10.1101/gr.278168.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Accepted: 11/21/2023] [Indexed: 12/19/2023]
Abstract
Meiotic recombination is crucial for human genetic diversity and chromosome segregation accuracy. Understanding its variation across individuals and the processes by which it goes awry are long-standing goals in human genetics. Current approaches for inferring recombination landscapes rely either on population genetic patterns of linkage disequilibrium (LD)-capturing a time-averaged view-or on direct detection of crossovers in gametes or multigeneration pedigrees, which limits data set scale and availability. Here, we introduce an approach for inferring sex-specific recombination landscapes using data from preimplantation genetic testing for aneuploidy (PGT-A). This method relies on low-coverage (<0.05×) whole-genome sequencing of in vitro fertilized (IVF) embryo biopsies. To overcome the data sparsity, our method exploits its inherent relatedness structure, knowledge of haplotypes from external population reference panels, and the frequent occurrence of monosomies in embryos, whereby the remaining chromosome is phased by default. Extensive simulations show our method's high accuracy, even at coverages as low as 0.02×. Applying this method to PGT-A data from 18,967 embryos, we mapped 70,660 recombination events with ∼150 kbp resolution, replicating established sex-specific recombination patterns. We observed a reduced total length of the female genetic map in trisomies compared with disomies, as well as chromosome-specific alterations in crossover distributions. Based on haplotype configurations in pericentromeric regions, our data indicate chromosome-specific propensities for different mechanisms of meiotic error. Our results provide a comprehensive view of the role of aberrant meiotic recombination in the origins of human aneuploidies and offer a versatile tool for mapping crossovers in low-coverage sequencing data from multiple siblings.
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Affiliation(s)
- Daniel Ariad
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA;
| | - Svetlana Madjunkova
- CReATe Fertility Centre, Toronto, Ontario M5G 1N8, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | | | - Siwei Chen
- CReATe Fertility Centre, Toronto, Ontario M5G 1N8, Canada
| | - Rina Abramov
- CReATe Fertility Centre, Toronto, Ontario M5G 1N8, Canada
| | - Clifford Librach
- CReATe Fertility Centre, Toronto, Ontario M5G 1N8, Canada
- Department of Obstetrics and Gynecology, University of Toronto, Toronto, Ontario M5G 1E2, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Ontario M5S 1A8, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Rajiv C McCoy
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA;
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3
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Fernandes JB, Naish M, Lian Q, Burns R, Tock AJ, Rabanal FA, Wlodzimierz P, Habring A, Nicholas RE, Weigel D, Mercier R, Henderson IR. Structural variation and DNA methylation shape the centromere-proximal meiotic crossover landscape in Arabidopsis. Genome Biol 2024; 25:30. [PMID: 38254210 PMCID: PMC10804481 DOI: 10.1186/s13059-024-03163-4] [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: 05/31/2023] [Accepted: 01/01/2024] [Indexed: 01/24/2024] Open
Abstract
BACKGROUND Centromeres load kinetochore complexes onto chromosomes, which mediate spindle attachment and allow segregation during cell division. Although centromeres perform a conserved cellular function, their underlying DNA sequences are highly divergent within and between species. Despite variability in DNA sequence, centromeres are also universally suppressed for meiotic crossover recombination, across eukaryotes. However, the genetic and epigenetic factors responsible for suppression of centromeric crossovers remain to be completely defined. RESULTS To explore the centromere-proximal meiotic recombination landscape, we map 14,397 crossovers against fully assembled Arabidopsis thaliana (A. thaliana) genomes. A. thaliana centromeres comprise megabase satellite repeat arrays that load nucleosomes containing the CENH3 histone variant. Each chromosome contains a structurally polymorphic region of ~3-4 megabases, which lack crossovers and include the satellite arrays. This polymorphic region is flanked by ~1-2 megabase low-recombination zones. These recombination-suppressed regions are enriched for Gypsy/Ty3 retrotransposons, and additionally contain expressed genes with high genetic diversity that initiate meiotic recombination, yet do not crossover. We map crossovers at high-resolution in proximity to CEN3, which resolves punctate centromere-proximal hotspots that overlap gene islands embedded in heterochromatin. Centromeres are densely DNA methylated and the recombination landscape is remodelled in DNA methylation mutants. We observe that the centromeric low-recombining zones decrease and increase crossovers in CG (met1) and non-CG (cmt3) mutants, respectively, whereas the core non-recombining zones remain suppressed. CONCLUSION Our work relates the genetic and epigenetic organization of A. thaliana centromeres and flanking pericentromeric heterochromatin to the zones of crossover suppression that surround the CENH3-occupied satellite repeat arrays.
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Affiliation(s)
- Joiselle B Fernandes
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, D-50829, Cologne, Germany
| | - Matthew Naish
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Qichao Lian
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, D-50829, Cologne, Germany
| | - Robin Burns
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Andrew J Tock
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Fernando A Rabanal
- Department of Molecular Biology, Max Planck Institute for Biology, Tübingen, D-72076, Tübingen, Germany
| | - Piotr Wlodzimierz
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Anette Habring
- Department of Molecular Biology, Max Planck Institute for Biology, Tübingen, D-72076, Tübingen, Germany
| | - Robert E Nicholas
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Detlef Weigel
- Department of Molecular Biology, Max Planck Institute for Biology, Tübingen, D-72076, Tübingen, Germany
- University of Tübingen, Institute for Bioinformatics and Medical Informatics, D-72076, Tübingen, Germany
| | - Raphael Mercier
- Department of Chromosome Biology, Max Planck Institute for Plant Breeding Research, D-50829, Cologne, Germany
| | - Ian R Henderson
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK.
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4
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Ariad D, Madjunkova S, Madjunkov M, Chen S, Abramov R, Librach C, McCoy RC. Aberrant landscapes of maternal meiotic crossovers contribute to aneuploidies in human embryos. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.07.543910. [PMID: 37333422 PMCID: PMC10274764 DOI: 10.1101/2023.06.07.543910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Meiotic recombination is crucial for human genetic diversity and chromosome segregation accuracy. Understanding its variation across individuals and the processes by which it goes awry are long-standing goals in human genetics. Current approaches for inferring recombination landscapes either rely on population genetic patterns of linkage disequilibrium (LD)-capturing a time-averaged view-or direct detection of crossovers in gametes or multi-generation pedigrees, which limits dataset scale and availability. Here, we introduce an approach for inferring sex-specific recombination landscapes using data from preimplantation genetic testing for aneuploidy (PGT-A). This method relies on low-coverage (<0.05×) whole-genome sequencing of in vitro fertilized (IVF) embryo biopsies. To overcome the data sparsity, our method exploits its inherent relatedness structure, knowledge of haplotypes from external population reference panels, as well as the frequent occurrence of monosomies in embryos, whereby the remaining chromosome is phased by default. Extensive simulations demonstrate our method's high accuracy, even at coverages as low as 0.02×. Applying this method to PGT-A data from 18,967 embryos, we mapped 70,660 recombination events with ~150 kbp resolution, replicating established sex-specific recombination patterns. We observed a reduced total length of the female genetic map in trisomies compared to disomies, as well as chromosome-specific alterations in crossover distributions. Based on haplotype configurations in pericentromeric regions, our data indicate chromosome-specific propensities for different mechanisms of meiotic error. Our results provide a comprehensive view of the role of aberrant meiotic recombination in the origins of human aneuploidies and offer a versatile tool for mapping crossovers in low-coverage sequencing data from multiple siblings.
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Affiliation(s)
- Daniel Ariad
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Svetlana Madjunkova
- CReATe Fertility Centre, Toronto, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
| | | | - Siwei Chen
- CReATe Fertility Centre, Toronto, Canada
| | | | - Clifford Librach
- CReATe Fertility Centre, Toronto, Canada
- Department of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
- Institute of Medical Sciences, University of Toronto, Toronto, Canada
- Department of Physiology, University of Toronto, Toronto, Canada
| | - Rajiv C. McCoy
- Department of Biology, Johns Hopkins University, Baltimore, MD, USA
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5
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Pazhayam NM, Frazier LK, Sekelsky J. Centromere-Proximal Suppression of Meiotic Crossovers in Drosophila is Robust to Changes in Centromere Number and Repetitive DNA Content. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.17.562696. [PMID: 37905008 PMCID: PMC10614898 DOI: 10.1101/2023.10.17.562696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Accurate segregation of homologous chromosomes during meiosis depends on both the presence and regulated placement of crossovers (COs). The centromere effect (CE), or CO exclusion in pericentromeric regions of the chromosome, is a meiotic CO patterning phenomenon that helps prevent nondisjunction (NDJ), thereby protecting against chromosomal disorders and other meiotic defects. Despite being identified nearly a century ago, the mechanisms behind this fundamental cellular process remain unknown, with most studies of the Drosophila CE focusing on local influences of the centromere and pericentric heterochromatin. In this study, we sought to investigate whether dosage changes in centromere number and repetitive DNA content affect the strength of the CE, using phenotypic recombination mapping. Additionally, we also studied the effects of repetitive DNA function on CE strength using satellite-DNA binding protein mutants shown to have defective centromere clustering. Despite what previous studies suggest, our results show that the Drosophila CE is robust to dosage changes in centromere number and repetitive DNA content, and potentially also to repetitive DNA function. Our study suggests that the CE is unlikely to be spatially controlled, providing novel insight into the mechanisms behind the Drosophila centromere effect.
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Affiliation(s)
- Nila M. Pazhayam
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Leah K. Frazier
- SURE-REU Program in Biological Mechanisms, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Integrative Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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6
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Sperling K, Scherb H, Neitzel H. Population monitoring of trisomy 21: problems and approaches. Mol Cytogenet 2023; 16:6. [PMID: 37183244 PMCID: PMC10183086 DOI: 10.1186/s13039-023-00637-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 05/02/2023] [Indexed: 05/16/2023] Open
Abstract
Trisomy 21 (Down syndrome) is the most common autosomal aneuploidy among newborns. About 90% result from meiotic nondisjunction during oogenesis, which occurs around conception, when also the most profound epigenetic modifications take place. Thus, maternal meiosis is an error prone process with an extreme sensitivity to endogenous factors, as exemplified by maternal age. This contrasts with the missing acceptance of causal exogenous factors. The proof of an environmental agent is a great challenge, both with respect to ascertainment bias, determination of time and dosage of exposure, as well as registration of the relevant individual health data affecting the birth prevalence. Based on a few exemplary epidemiological studies the feasibility of trisomy 21 monitoring is illustrated. In the nearer future the methodical premises will be clearly improved, both due to the establishment of electronic health registers and to the introduction of non-invasive prenatal tests. Down syndrome is a sentinel phenotype, presumably also with regard to other congenital anomalies. Thus, monitoring of trisomy 21 offers new chances for risk avoidance and preventive measures, but also for basic research concerning identification of relevant genomic variants involved in chromosomal nondisjunction.
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Affiliation(s)
- Karl Sperling
- Institute of Medical and Human Genetics, Charité-Universitaetsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.
| | - Hagen Scherb
- Institute of Computational Biology, Helmholtz Zentrum München - German Research Center for Environmental Health, Neuherberg, Germany
| | - Heidemarie Neitzel
- Institute of Medical and Human Genetics, Charité-Universitaetsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
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7
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Yang J, Wang Y, Li C, Han W, Liu W, Xiong S, Zhang Q, Tong K, Huang G, Zhang X. Variation of Female Pronucleus Reveals Oocyte or Embryo Chromosomal Copy Number Variations. ADVANCED GENETICS (HOBOKEN, N.J.) 2023; 4:2200001. [PMID: 36910589 PMCID: PMC10000260 DOI: 10.1002/ggn2.202200001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 09/20/2022] [Indexed: 11/11/2022]
Abstract
The characteristics of the human pronuclei (PNs), which exist 16-22 h after fertilization, appear to serve as good indicators to evaluate the quality of human oocyte and embryo, and may reflect the status of female and male chromosome composition. Here, a quantitative PN measurement method that is generated by applying expert experience combined with deep learning from large annotated datasets is reported. After mathematic reconstruction of PNs, significant differences are obtained in chromosome-normal rate and chromosomal small errors such as copy number variants by comparing the size of the reconstructive female PN. After integrating the whole procedure of PN dynamics and adjusting for errors that occur during PN identification, the results are robust. Notably, all positive prediction results are obtained from the female propositus population. Thus, the size of female PNs may mirror the internal quality of the chromosomal integrity of the oocyte. Embryos that develop from zygotes with larger female PNs may have a reduced risk of copy number variations.
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Affiliation(s)
- Jingwei Yang
- Center for Reproductive Medicine Women and Children's Hospital of Chongqing Medical University Chongqing Health Center for Women and Children Chongqing 400010 China.,Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China
| | - Yikang Wang
- Department of Mechatronics Graduate School of Medicine, Engineering, and Agricultural Sciences University of Yamanashi Yamanashi-ken 400-8510 Japan
| | - Chong Li
- Center for Reproductive Medicine Women and Children's Hospital of Chongqing Medical University Chongqing Health Center for Women and Children Chongqing 400010 China.,Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China
| | - Wei Han
- Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China.,Chongqing Clinical Research Center for Reprodutive Medicine Chongqing 400010 China
| | - Weiwei Liu
- Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China.,Chongqing Clinical Research Center for Reprodutive Medicine Chongqing 400010 China
| | - Shun Xiong
- Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China.,Chongqing Clinical Research Center for Reprodutive Medicine Chongqing 400010 China
| | - Qi Zhang
- Center for Reproductive Medicine Women and Children's Hospital of Chongqing Medical University Chongqing Health Center for Women and Children Chongqing 400010 China.,Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China
| | - Keya Tong
- Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China.,Chongqing Clinical Research Center for Reprodutive Medicine Chongqing 400010 China
| | - Guoning Huang
- Center for Reproductive Medicine Women and Children's Hospital of Chongqing Medical University Chongqing Health Center for Women and Children Chongqing 400010 China.,Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China.,Chongqing Clinical Research Center for Reprodutive Medicine Chongqing 400010 China
| | - Xiaodong Zhang
- Center for Reproductive Medicine Women and Children's Hospital of Chongqing Medical University Chongqing Health Center for Women and Children Chongqing 400010 China.,Chongqing Key Laboratory of Human embryo Engineering Chongqing 400010 China.,Chongqing Clinical Research Center for Reprodutive Medicine Chongqing 400010 China
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8
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Soriano J, Belmonte-Tebar A, de la Casa-Esperon E. Synaptonemal & CO analyzer: A tool for synaptonemal complex and crossover analysis in immunofluorescence images. Front Cell Dev Biol 2023; 11:1005145. [PMID: 36743415 PMCID: PMC9894712 DOI: 10.3389/fcell.2023.1005145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 01/09/2023] [Indexed: 01/20/2023] Open
Abstract
During the formation of ova and sperm, homologous chromosomes get physically attached through the synaptonemal complex and exchange DNA at crossover sites by a process known as meiotic recombination. Chromosomes that do not recombine or have anomalous crossover distributions often separate poorly during the subsequent cell division and end up in abnormal numbers in ova or sperm, which can lead to miscarriage or developmental defects. Crossover numbers and distribution along the synaptonemal complex can be visualized by immunofluorescent microscopy. However, manual analysis of large numbers of cells is very time-consuming and a major bottleneck for recombination studies. Some image analysis tools have been created to overcome this situation, but they are not readily available, do not provide synaptonemal complex data, or do not tackle common experimental difficulties, such as overlapping chromosomes. To overcome these limitations, we have created and validated an open-source ImageJ macro routine that facilitates and speeds up the crossover and synaptonemal complex analyses in mouse chromosome spreads, as well as in other vertebrate species. It is free, easy to use and fulfills the recommendations for enhancing rigor and reproducibility in biomedical studies.
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Affiliation(s)
- Joaquim Soriano
- Centro Regional de Investigaciones Biomédicas (CRIB), Universidad de Castilla-La Mancha, Albacete, Spain
| | - Angela Belmonte-Tebar
- Centro Regional de Investigaciones Biomédicas (CRIB), Universidad de Castilla-La Mancha, Albacete, Spain
| | - Elena de la Casa-Esperon
- Centro Regional de Investigaciones Biomédicas (CRIB), Universidad de Castilla-La Mancha, Albacete, Spain,Biology of Cell Growth, Differentiation and Activation Group, Department of Inorganic and Organic Chemistry and Biochemistry, School of Pharmacy, Universidad de Castilla-La Mancha, Albacete, Spain,*Correspondence: Elena de la Casa-Esperon,
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9
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Sen S, Dodamani A, Nambiar M. Emerging mechanisms and roles of meiotic crossover repression at centromeres. Curr Top Dev Biol 2022; 151:155-190. [PMID: 36681469 DOI: 10.1016/bs.ctdb.2022.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Crossover events during recombination in meiosis are essential for generating genetic diversity as well as crucial to allow accurate chromosomal segregation between homologous chromosomes. Spatial control for the distribution of crossover events along the chromosomes is largely a tightly regulated process and involves many facets such as interference, repression as well as assurance, to make sure that not too many or too few crossovers are generated. Repression of crossover events at the centromeres is a highly conserved process across all species tested. Failure to inhibit such recombination events can result in chromosomal mis-segregation during meiosis resulting in aneuploid gametes that are responsible for infertility or developmental disorders such as Down's syndrome and other trisomies in humans. In the past few decades, studies to understand the molecular mechanisms behind this repression have shown the involvement of a multitude of factors ranging from the centromere-specific proteins such as the kinetochore to the flanking pericentric heterochromatin as well as DNA double-strand break repair pathways. In this chapter, we review the different mechanisms of pericentric repression mechanisms known till date as well as highlight the importance of understanding this regulation in the context of chromosomal segregation defects. We also discuss the clinical implications of dysregulation of this process, especially in human reproductive health and genetic diseases.
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Affiliation(s)
- Sucharita Sen
- Department of Biology, Indian Institute of Science Education and Research, Pune, India
| | - Ananya Dodamani
- Department of Biology, Indian Institute of Science Education and Research, Pune, India
| | - Mridula Nambiar
- Department of Biology, Indian Institute of Science Education and Research, Pune, India.
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10
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Liu G, Sun Y, Jia L, Li R, Zuo Y. Chromatin accessibility shapes meiotic recombination in mouse primordial germ cells through assisting double-strand breaks and loop formation. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2022; 1865:194844. [PMID: 35870788 DOI: 10.1016/j.bbagrm.2022.194844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/27/2022] [Accepted: 07/09/2022] [Indexed: 06/15/2023]
Abstract
Meiotic recombination is a driver of evolution, and aberrant recombination is a major contributor to aneuploidy in mammals. Mechanism of recombination remains elusive yet. Here, we present a computational analysis to explore recombination-related dynamics of chromatin accessibility in mouse primordial germ cells (PGCs). Our data reveals that: (1) recombination hotspots which get accessible at meiosis-specific DNase I-hypersensitive sites (DHSs) only when PGCs enter meiosis are located preferentially in intronic and distal intergenic regions; (2) stable DHSs maintained stably across PGC differentiation are enriched by CTCF motifs and CTCF binding and mediate chromatin loop formation; (3) compared with the specific DHSs aroused at meiotic stage, stable DHSs are largely encoded in DNA sequence and also enriched by epigenetic marks; (4) PRDM9 is likely to target nucleosome-occupied hotspot regions and remodels local chromatin structure to make them accessible for recombination machinery; and (5) cells undergoing meiotic recombination are deficient in TAD structure and chromatin loop arrays are organized regularly along the axis formed between homologous chromosomes. Taken together, by analyzing DHS-related DNA features, epigenetic marks and 3D genome structure, we revealed some specific roles of chromatin accessibility in recombination, which would expand our understanding of recombination mechanism.
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Affiliation(s)
- Guoqing Liu
- School of Life Science and Technology, Inner Mongolia University of Science and Technology, Baotou, China; Inner Mongolia Key Laboratory of Functional Genomics and Bioinformatics, Inner Mongolia University of Science and Technology, Baotou, China; School of Life Sciences, Peking University, Beijing, China.
| | - Yu Sun
- School of Life Sciences, Inner Mongolia University, Hohhot, China
| | - Lumeng Jia
- School of Life Sciences, Peking University, Beijing, China
| | - Ruifeng Li
- School of Life Sciences, Peking University, Beijing, China
| | - Yongchun Zuo
- School of Life Sciences, Inner Mongolia University, Hohhot, China.
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11
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Haplotype-aware inference of human chromosome abnormalities. Proc Natl Acad Sci U S A 2021; 118:2109307118. [PMID: 34772814 DOI: 10.1073/pnas.2109307118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/16/2021] [Indexed: 12/25/2022] Open
Abstract
Extra or missing chromosomes-a phenomenon termed aneuploidy-frequently arise during human meiosis and embryonic mitosis and are the leading cause of pregnancy loss, including in the context of in vitro fertilization (IVF). While meiotic aneuploidies affect all cells and are deleterious, mitotic errors generate mosaicism, which may be compatible with healthy live birth. Large-scale abnormalities such as triploidy and haploidy also contribute to adverse pregnancy outcomes, but remain hidden from standard sequencing-based approaches to preimplantation genetic testing for aneuploidy (PGT-A). The ability to reliably distinguish meiotic and mitotic aneuploidies, as well as abnormalities in genome-wide ploidy, may thus prove valuable for enhancing IVF outcomes. Here, we describe a statistical method for distinguishing these forms of aneuploidy based on analysis of low-coverage whole-genome sequencing data, which is the current standard in the field. Our approach overcomes the sparse nature of the data by leveraging allele frequencies and linkage disequilibrium (LD) measured in a population reference panel. The method, which we term LD-informed PGT-A (LD-PGTA), retains high accuracy down to coverage as low as 0.05 × and at higher coverage can also distinguish between meiosis I and meiosis II errors based on signatures spanning the centromeres. LD-PGTA provides fundamental insight into the origins of human chromosome abnormalities, as well as a practical tool with the potential to improve genetic testing during IVF.
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12
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Pazhayam NM, Turcotte CA, Sekelsky J. Meiotic Crossover Patterning. Front Cell Dev Biol 2021; 9:681123. [PMID: 34368131 PMCID: PMC8344875 DOI: 10.3389/fcell.2021.681123] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 06/28/2021] [Indexed: 12/02/2022] Open
Abstract
Proper number and placement of meiotic crossovers is vital to chromosome segregation, with failures in normal crossover distribution often resulting in aneuploidy and infertility. Meiotic crossovers are formed via homologous repair of programmed double-strand breaks (DSBs). Although DSBs occur throughout the genome, crossover placement is intricately patterned, as observed first in early genetic studies by Muller and Sturtevant. Three types of patterning events have been identified. Interference, first described by Sturtevant in 1915, is a phenomenon in which crossovers on the same chromosome do not occur near one another. Assurance, initially identified by Owen in 1949, describes the phenomenon in which a minimum of one crossover is formed per chromosome pair. Suppression, first observed by Beadle in 1932, dictates that crossovers do not occur in regions surrounding the centromere and telomeres. The mechanisms behind crossover patterning remain largely unknown, and key players appear to act at all scales, from the DNA level to inter-chromosome interactions. There is also considerable overlap between the known players that drive each patterning phenomenon. In this review we discuss the history of studies of crossover patterning, developments in methods used in the field, and our current understanding of the interplay between patterning phenomena.
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Affiliation(s)
- Nila M. Pazhayam
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Carolyn A. Turcotte
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
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13
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Chatzidaki EE, Powell S, Dequeker BJH, Gassler J, Silva MCC, Tachibana K. Ovulation suppression protects against chromosomal abnormalities in mouse eggs at advanced maternal age. Curr Biol 2021; 31:4038-4051.e7. [PMID: 34314679 DOI: 10.1016/j.cub.2021.06.076] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 04/01/2021] [Accepted: 06/25/2021] [Indexed: 01/09/2023]
Abstract
The frequency of egg aneuploidy and trisomic pregnancies increases with maternal age. To what extent individual approaches can delay the "maternal age effect" is unclear because multiple causes contribute to chromosomal abnormalities in mammalian eggs. We propose that ovulation frequency determines the physiological aging of oocytes, a key aspect of which is the ability to accurately segregate chromosomes and produce euploid eggs. To test this hypothesis, ovulations were reduced using successive pregnancies, hormonal contraception, and a pre-pubertal knockout mouse model, and the effects on chromosome segregation and egg ploidy were examined. We show that each intervention reduces chromosomal abnormalities in eggs of aged mice, suggesting that ovulation reduction delays oocyte aging. The protective effect can be partly explained by retention of chromosomal Rec8-cohesin that maintains sister chromatid cohesion in meiosis. In addition, single-nucleus Hi-C (snHi-C) revealed deterioration in the 3D chromatin structure including an increase in extruded loop sizes in long-lived oocytes. Artificial cleavage of Rec8 is sufficient to increase extruded loop sizes, suggesting that cohesin complexes maintaining cohesion restrict loop extrusion. These findings suggest that ovulation suppression protects against Rec8 loss, thereby maintaining both sister chromatid cohesion and 3D chromatin structure and promoting production of euploid eggs. We conclude that the maternal age effect can be delayed in mice. An implication of this work is that long-term ovulation-suppressing conditions can potentially reduce the risk of aneuploid pregnancies at advanced maternal age.
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Affiliation(s)
- Emmanouella E Chatzidaki
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Sean Powell
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Bart J H Dequeker
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Johanna Gassler
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Mariana C C Silva
- Research Institute of Molecular Pathology, Campus Vienna BioCenter 1, 1030 Vienna, Austria
| | - Kikuë Tachibana
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Dr. Bohr-Gasse 3, 1030 Vienna, Austria; Department of Totipotency, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Munich, Germany.
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14
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Blastomere movement correlates with ploidy and mosaicism in early-stage human embryos after in vitro fertilization. ZYGOTE 2021; 30:25-39. [PMID: 34275512 DOI: 10.1017/s0967199420000817] [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] [Indexed: 11/07/2022]
Abstract
Embryos undergo chaotic division and decrease in quality on day 3 with a reduction in the rates of subsequent blastocyst formation. Disordered cleavage causes a deterioration in embryonic quality, here we assessed the relationship between an cleavage model in first mitosis and the chromosomal status of human embryos, and discuss the potential biological and clinical implications for the cleavage model as a single parameter that can be used to assess embryonic quality. Thirty-two infertile couples, with normal karyotypes and who underwent their first IVF cycle were recruited to donate one normal two-cell-stage embryo each for this study between 2019 and 2020. Twenty-eight two-cell embryos underwent preimplantation genetic testing of each blastomere, and four chaotic-division embryos were stained with Hoechst and cultured in a confocal laser-scanning microscopy incubator system. This system showed high specificity and PPV but low sensitivity and NPV using the CM in the prediction of euploidy, indicating that CM could be considered a screening method for embryo selection; additional observational studies using the CM to select transferable embryos are needed before it can be used in clinical practice.
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15
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Chen CP, Huang WC, Chern SR, Chen SW, Wu FT, Lee MS, Wang W. Detection of paternal origin of fetal trisomy 21 in a pregnancy with isolated ventriculomegaly but without advanced parental age. Taiwan J Obstet Gynecol 2021; 59:610-612. [PMID: 32653140 DOI: 10.1016/j.tjog.2020.05.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/11/2020] [Indexed: 10/23/2022] Open
Abstract
OBJECTIVE We present detection of paternal origin of fetal trisomy 21 in a pregnancy with isolated ventriculomegaly but without advanced parental age. CASE REPORT A 29-year-old pregnant woman was admitted to the hospital at 18 weeks of gestation for tocolytic treatment because of irregular uterine contractions. Her husband was 30 years old. The couple had a healthy daughter. Prenatal ultrasound incidentally found isolated ventriculomegaly, and subsequent amniocentesis revealed a karyotype of 47,XX,+21 in 20/20 colonies of cultured amniocytes. The pregnancy was terminated, and the fetus manifested characteristic craniofacial appearance of Down syndrome and hyposplastic middle phalanx of the fifth finger. Postnatal polymorphic DNA marker analysis on the DNAs extracted from the cord blood and parental bloods using quantitative fluorescent polymerase chain reaction (QF-PCR) showed a paternal origin of fetal trisomy 21. The father had a karyotype of 46, XY in 40/40 blood lymphocytes. CONCLUSION QF-PCR is useful for rapid confirmation of prenatally detected fetal trisomy 21 and determination of paternal origin of fetal trisomy 21 especially in pregnancies with fetal structural abnormalities but without advanced parental age.
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Affiliation(s)
- Chih-Ping Chen
- Department of Obstetrics and Gynecology, MacKay Memorial Hospital, Taipei, Taiwan; Department of Medical Research, MacKay Memorial Hospital, Taipei, Taiwan; Department of Biotechnology, Asia University, Taichung, Taiwan; School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan; Institute of Clinical and Community Health Nursing, National Yang-Ming University, Taipei, Taiwan; Department of Obstetrics and Gynecology, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
| | - Wan-Chun Huang
- Department of Obstetrics and Gynecology, MacKay Memorial Hospital, Taipei, Taiwan
| | - Schu-Rern Chern
- Department of Medical Research, MacKay Memorial Hospital, Taipei, Taiwan
| | - Shin-Wen Chen
- Department of Obstetrics and Gynecology, MacKay Memorial Hospital, Taipei, Taiwan
| | - Fang-Tzu Wu
- Department of Obstetrics and Gynecology, MacKay Memorial Hospital, Taipei, Taiwan
| | - Meng-Shan Lee
- Department of Obstetrics and Gynecology, MacKay Memorial Hospital, Taipei, Taiwan
| | - Wayseen Wang
- Department of Medical Research, MacKay Memorial Hospital, Taipei, Taiwan; Department of Bioengineering, Tatung University, Taipei, Taiwan
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16
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The effect of Telomere Lengthening on Genetic Diseases. JOURNAL OF CONTEMPORARY MEDICINE 2021. [DOI: 10.16899/jcm.756562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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17
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Pal U, Halder P, Ray A, Sarkar S, Datta S, Ghosh P, Ghosh S. The etiology of Down syndrome: Maternal MCM9 polymorphisms increase risk of reduced recombination and nondisjunction of chromosome 21 during meiosis I within oocyte. PLoS Genet 2021; 17:e1009462. [PMID: 33750944 PMCID: PMC8021012 DOI: 10.1371/journal.pgen.1009462] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 04/01/2021] [Accepted: 03/03/2021] [Indexed: 11/21/2022] Open
Abstract
Altered patterns of recombination on 21q have long been associated with the nondisjunction chromosome 21 within oocytes and the increased risk of having a child with Down syndrome. Unfortunately the genetic etiology of these altered patterns of recombination have yet to be elucidated. We for the first time genotyped the gene MCM9, a candidate gene for recombination regulation and DNA repair in mothers with or without children with Down syndrome. In our approach, we identified the location of recombination on the maternal chromosome 21 using short tandem repeat markers, then stratified our population by the origin of meiotic error and age at conception. We observed that twenty-five out of forty-one single nucleotide polymorphic sites within MCM9 exhibited an association with meiosis I error (N = 700), but not with meiosis II error (N = 125). This association was maternal age-independent. Several variants exhibited aprotective association with MI error, some were neutral. Maternal age stratified characterization of cases revealed that MCM9 risk variants were associated with an increased chance of reduced recombination on 21q within oocytes. The spatial distribution of single observed recombination events revealed no significant change in the location of recombination among women harbouring MCM9 risk, protective, or neutral variant. Additionally, we identified a total of six novel polymorphic variants and two novel alleles that were either risk imparting or protective against meiosis I nondisjunction. In silico analyses using five different programs suggest the risk variants either cause a change in protein function or may alter the splicing pattern of transcripts and disrupt the proportion of different isoforms of MCM9 products within oocytes. These observations bring us a significant step closer to understanding the molecular basis of recombination errors in chromosome 21 nondisjunction within oocytes that leads to birth of child with Down syndrome. We studied MCM9 variations in the genome of women with a Down syndrome child by stratifying the women based on MCM9 genotypes, meiotic error group, and their age of conception. We identified polymorphisms are associated with reduced recombination and nondisjunction of chromosome 21 at the meiosis I stage of oogenesis in a maternal age-independent manner. But these variants do not affect the position of chiasma formation. In Silico analyses revealed the presence of MCM9 variants that may cause alteration in protein function due to amino acid substitution. We also identified splice variants in MCM9. We hypothesize that the polymorphisms in MCM9 predispose women to experience reduced recombination on chromosome 21 in oocytes at meiosis I, which ultimately leads to the birth of a child with Down syndrome.
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Affiliation(s)
- Upamanyu Pal
- Cytogenetics and Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath Palit Siksha Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
| | - Pinku Halder
- Cytogenetics and Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath Palit Siksha Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
| | - Anirban Ray
- Department of Zoology, Bangabasi Morning College (affiliated to University of Calcutta), Kolkata, West Bengal, India
| | - Sumantra Sarkar
- Department of Paediatric Medicine, Institute of Post Graduate Medical Education and Research (IPGMER), Bhowanipore, Kolkata, West Bengal, India
- Department of Paediatric Medicine, Diamond Harbour Government Medical College & Hospital, Diamond Harbour, West Bengal, India
| | - Supratim Datta
- Department of Paediatric Medicine, Institute of Post Graduate Medical Education and Research (IPGMER), Bhowanipore, Kolkata, West Bengal, India
| | - Papiya Ghosh
- Department of Zoology, Bijoykrishna Girls’ College (Affiliated to University of Calcutta), Howrah, West Bengal, India
| | - Sujay Ghosh
- Cytogenetics and Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath Palit Siksha Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
- * E-mail:
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18
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Chernus JM, Sherman SL, Feingold E. Analyses stratified by maternal age and recombination further characterize genes associated with maternal nondisjunction of chromosome 21. Prenat Diagn 2021; 41:591-609. [PMID: 33596328 DOI: 10.1002/pd.5919] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 01/17/2021] [Accepted: 02/02/2021] [Indexed: 12/22/2022]
Abstract
OBJECTIVE In our previous work, we performed the first genome-wide association study to find genetic risk factors for maternal nondisjunction of chromosome 21. The objective of the current work was to perform stratified analyses of the same dataset to further elucidate potential mechanisms of genetic risk factors. METHODS We focused on loci that were statistically significantly associated with maternal nondisjunction based on this same dataset in our previous study and performed stratified association analyses in seven subgroups defined by age and meiotic recombination profile. In each analysis, we contrasted a different subgroup of mothers with the same set of fathers, the mothers serving as cases (phenotype: meiotic nondisjunction of chromosome 21) and the fathers as controls. RESULTS Our stratified analyses identified several genes whose patterns of association are consistent with generalized effects across groups, as well as other genes that are consistent with specific effects in certain groups. CONCLUSIONS While our results are epidemiological in nature and cannot conclusively prove mechanisms, we identified a number of patterns that are consistent with specific mechanisms. In many cases those mechanisms are strongly supported by available literature on the associated genes.
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Affiliation(s)
- Jonathan M Chernus
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Stephanie L Sherman
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Eleanor Feingold
- Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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19
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Innan H, Vaiman D, Veitia RA. Predictable increase in female reproductive window: A simple model connecting age of reproduction, menopause, and longevity. Bioessays 2021; 43:e2000233. [PMID: 33569823 DOI: 10.1002/bies.202000233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 01/22/2021] [Accepted: 01/27/2021] [Indexed: 01/08/2023]
Abstract
With the ever-increasing lifespan along with societal changes, women can marry and procreate later than in previous centuries. However, pathogenic genetic variants segregating in the population can lead to female subfertility or infertility well before the average age of normal menopause, leading to counter-selection of such deleterious alleles. In reviewing this field, we speculate that a logical consequence would be the later occurrence of menopause and the extension of women's reproductive lifespan. We illustrate this point with a simple model that applies to other variants that contribute to female infertility, including epigenetic variation. We also consider the effect of medical interventions and lifestyle.
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Affiliation(s)
- Hideki Innan
- Graduate University for Advanced Studies, Hayama, Kanagawa, Japan
| | - Daniel Vaiman
- Université de Paris, Paris, France.,Institut Cochin, Paris, France
| | - Reiner A Veitia
- Université de Paris, Paris, France.,CNRS, Institut Jacques Monod, Paris, France.,Institut de Biologie François Jacob, Commissariat à l'Energie Atomique et aux Energies Alternatives, Université Paris-Saclay, Paris, France
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20
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Hassold T, Maylor-Hagen H, Wood A, Gruhn J, Hoffmann E, Broman KW, Hunt P. Failure to recombine is a common feature of human oogenesis. Am J Hum Genet 2021; 108:16-24. [PMID: 33306948 PMCID: PMC7820622 DOI: 10.1016/j.ajhg.2020.11.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Accepted: 11/09/2020] [Indexed: 12/16/2022] Open
Abstract
Failure of homologous chromosomes to recombine is arguably the most important cause of human meiotic nondisjunction, having been linked to numerous autosomal and sex chromosome trisomies of maternal origin. However, almost all information on these "exchangeless" homologs has come from genetic mapping studies of trisomic conceptuses, so the incidence of this defect and its impact on gametogenesis are not clear. If oocytes containing exchangeless homologs are selected against during meiosis, the incidence may be much higher in developing germ cells than in zygotes. To address this, we initiated studies of exchangeless chromosomes in fetal ovarian samples from elective terminations of pregnancy. In total, we examined more than 7,000 oocytes from 160 tissue samples, scoring for the number of foci per cell of the crossover-associated protein MLH1. We identified a surprisingly high level of recombination failure, with more than 7% of oocytes containing at least one chromosome pair that lacked an MLH1 focus. Detailed analyses indicate striking chromosome-specific differences, with a preponderance of MLH1-less homologs involving chromosomes 21 or 22. Further, the effect was linked to the overall level of recombination in the cell, with the presence of one or two exchangeless chromosomes in a cell associated with a 10%-20% reduction in the total number of crossovers. This suggests individuals with lower rates of meiotic recombination are at an increased risk of producing aneuploid offspring.
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Affiliation(s)
- Terry Hassold
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA.
| | - Heather Maylor-Hagen
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Anna Wood
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
| | - Jennifer Gruhn
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA; DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, NK 2200, Denmark
| | - Eva Hoffmann
- DNRF Center for Chromosome Stability, Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, NK 2200, Denmark
| | - Karl W Broman
- Department of Biostatistics and Medical Informatics, University of Wisconsin, Madison, WI 53706, USA
| | - Patricia Hunt
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA
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21
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Mogessie B. Advances and surprises in a decade of oocyte meiosis research. Essays Biochem 2020; 64:263-275. [PMID: 32538429 DOI: 10.1042/ebc20190068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 05/22/2020] [Accepted: 05/26/2020] [Indexed: 12/30/2022]
Abstract
Eggs are produced from progenitor oocytes through meiotic cell division. Fidelity of meiosis is critical for healthy embryogenesis - fertilisation of aneuploid eggs that contain the wrong number of chromosomes is a leading cause of genetic disorders including Down's syndrome, human embryo deaths and infertility. Incidence of meiosis-related oocyte and egg aneuploidies increases dramatically with advancing maternal age, which further complicates the 'meiosis problem'. We have just emerged from a decade of meiosis research that was packed with exciting and transformative research. This minireview will focus primarily on studies of mechanisms that directly influence chromosome segregation.
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Affiliation(s)
- Binyam Mogessie
- School of Biochemistry, University of Bristol, Bristol BS8 1TD, U.K
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22
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Smith GR, Nambiar M. New Solutions to Old Problems: Molecular Mechanisms of Meiotic Crossover Control. Trends Genet 2020; 36:337-346. [PMID: 32294414 PMCID: PMC7162993 DOI: 10.1016/j.tig.2020.02.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 02/10/2020] [Accepted: 02/12/2020] [Indexed: 01/25/2023]
Abstract
During scientific investigations, the explanation of remarkably interesting phenomena must often await development of new methods or accrual of new observations that in retrospect can lead to lucid answers to the initial problem. A case in point is the control of genetic recombination during meiosis, which leads to crossovers between chromosomes critical for production of healthy offspring. Crossovers must be properly placed along meiotic chromosomes for their accurate segregation. Here, we review observations on two aspects of meiotic crossover control - crossover interference and repression of crossovers near centromeres, both observed more than 85 years ago. Only recently have relatively simple molecular mechanisms for these phenomena become clear through advances in both methods and understanding the molecular basis of meiotic recombination.
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Affiliation(s)
- Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
| | - Mridula Nambiar
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA; Department of Biology, Indian Institute of Science Education and Research, Pune, India
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23
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Hughes SE, Hawley RS. Meiosis: Location, Location, Location, How Crossovers Ensure Segregation. Curr Biol 2020; 30:R311-R313. [PMID: 32259504 DOI: 10.1016/j.cub.2020.02.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The proper behavior of homologous chromosomes at the first meiotic division is usually ensured by crossing over. A new study shows that crossover position influences the successful completion of the chromatin remodeling processes that facilitate homologous segregation.
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Affiliation(s)
- Stacie E Hughes
- Stowers Institute for Medical Research, 1000 E. 50(th) St., Kansas City, MO 64110, USA
| | - R Scott Hawley
- Stowers Institute for Medical Research, 1000 E. 50(th) St., Kansas City, MO 64110, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160, USA.
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24
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Babakhanzadeh E, Nazari M, Ghasemifar S, Khodadadian A. Some of the Factors Involved in Male Infertility: A Prospective Review. Int J Gen Med 2020; 13:29-41. [PMID: 32104049 PMCID: PMC7008178 DOI: 10.2147/ijgm.s241099] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 01/23/2020] [Indexed: 01/04/2023] Open
Abstract
Infertility is defined as the inability of couples to have a baby after one year of regular unprotected intercourse, affecting 10 to 15% of couples. According to the latest WHO statistics, approximately 50-80 million people worldwide sufer from infertility, and male factors are responsible for approximately 20-30% of all infertility cases. The diagnosis of infertility in men is mainly based on semen analysis. The main parameters of semen include: concentration, appearance and motility of sperm. Causes of infertility in men include a variety of things including hormonal disorders, physical problems, lifestyle problems, psychological issues, sex problems, chromosomal abnormalities and single-gene defects. Despite numerous efforts by researchers to identify the underlying causes of male infertility, about 70% of cases remain unknown. These statistics show a lack of understanding of the mechanisms involved in male infertility. This article focuses on the histology of testicular tissue samples, the male reproductive structure, factors affecting male infertility, strategies available to find genes involved in infertility, existing therapeutic methods for male infertility, and sperm recovery in infertile men.
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Affiliation(s)
- Emad Babakhanzadeh
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.,Research and Clinical Center for Infertility, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Majid Nazari
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Sina Ghasemifar
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Ali Khodadadian
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
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25
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A candidate gene analysis and GWAS for genes associated with maternal nondisjunction of chromosome 21. PLoS Genet 2019; 15:e1008414. [PMID: 31830031 PMCID: PMC6932832 DOI: 10.1371/journal.pgen.1008414] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 12/26/2019] [Accepted: 09/11/2019] [Indexed: 01/21/2023] Open
Abstract
Human nondisjunction errors in oocytes are the leading cause of pregnancy loss, and for pregnancies that continue to term, the leading cause of intellectual disabilities and birth defects. For the first time, we have conducted a candidate gene and genome-wide association study to identify genes associated with maternal nondisjunction of chromosome 21 as a first step to understand predisposing factors. A total of 2,186 study participants were genotyped on the HumanOmniExpressExome-8v1-2 array. These participants included 749 live birth offspring with standard trisomy 21 and 1,437 parents. Genotypes from the parents and child were then used to identify mothers with nondisjunction errors derived in the oocyte and to establish the type of error (meiosis I or meiosis II). We performed a unique set of subgroup comparisons designed to leverage our previous work suggesting that the etiologies of meiosis I and meiosis II nondisjunction differ for trisomy 21. For the candidate gene analysis, we selected genes associated with chromosome dynamics early in meiosis and genes associated with human global recombination counts. Several candidate genes showed strong associations with maternal nondisjunction of chromosome 21, demonstrating that genetic variants associated with normal variation in meiotic processes can be risk factors for nondisjunction. The genome-wide analysis also suggested several new potentially associated loci, although follow-up studies using independent samples are required. Approximately one of every 700 babies is born with trisomy 21—an extra copy of chromosome 21. Trisomy 21 is caused by the failure of chromosomes to segregate properly during meiosis, generally in the mother. Past studies have defined altered patterns of recombination along nondisjoined chromosomes as risk factors for human nondisjunction and model systems have clearly shown that specific genes involved recombination and other early meiotic processes play a role in the fidelity of chromosome segregation. However, no genome-wide genetic study (GWAS) has ever been conducted using maternal human nondisjunction as the disease phenotype. This study takes the first step to understand predisposing factors. We used chromosome 21 genotypes from the parents and child to identify mothers with nondisjunction errors derived in the oocyte and to establish the type of error (meiosis I or meiosis II). We then conducted a unique set of subgroup comparisons designed to leverage our previous work that shows that the etiologies of meiosis I and meiosis II nondisjunction differ for trisomy 21. Both the candidate gene study and the GWAS provide evidence that meiotic-specific structures and processes are vulnerable to genetic variants that lead to increased risk of human chromosome nondisjunction.
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26
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Abstract
Chromosome segregation errors in human oocytes lead to aneuploid embryos that cause infertility and birth defects. Here we provide an overview of the chromosome-segregation process in the mammalian oocyte, highlighting mechanistic differences between oocytes and somatic cells that render oocytes so prone to segregation error. These differences include the extremely large size of the oocyte cytoplasm, the unique geometry of meiosis-I chromosomes, idiosyncratic function of the spindle assembly checkpoint, and dramatically altered oocyte cell-cycle control and spindle assembly, as compared to typical somatic cells. We summarise recent work suggesting that aging leads to a further deterioration in fidelity of chromosome segregation by impacting multiple components of the chromosome-segregation machinery. In addition, we compare and contrast recent results from mouse and human oocytes, which exhibit overlapping defects to differing extents. We conclude that the striking propensity of the oocyte to mis-segregate chromosomes reflects the unique challenges faced by the spindle in a highly unusual cellular environment.
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Affiliation(s)
- Aleksandar I Mihajlović
- Centre Recherche CHUM and Department OBGYN, Université de Montreal, Montreal, Quebec, Canada
| | - Greg FitzHarris
- Centre Recherche CHUM and Department OBGYN, Université de Montreal, Montreal, Quebec, Canada.
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Hartmann M, Umbanhowar J, Sekelsky J. Centromere-Proximal Meiotic Crossovers in Drosophila melanogaster Are Suppressed by Both Highly Repetitive Heterochromatin and Proximity to the Centromere. Genetics 2019; 213:113-125. [PMID: 31345993 PMCID: PMC6727794 DOI: 10.1534/genetics.119.302509] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 07/19/2019] [Indexed: 11/18/2022] Open
Abstract
Crossovers are essential in meiosis of most organisms to ensure the proper segregation of chromosomes, but improper placement of crossovers can result in nondisjunction and aneuploidy in progeny. In particular, crossovers near the centromere can cause nondisjunction. Centromere-proximal crossovers are suppressed by what is termed the centromere effect, but the mechanism is unknown. Here, we investigate contributions to centromere-proximal crossover suppression in Drosophila melanogaster We mapped a large number of centromere-proximal crossovers, and find that crossovers are essentially absent from the highly repetitive (HR)-heterochromatin surrounding the centromere but occur at a low frequency within the less-repetitive (LR)-heterochromatic region and adjacent euchromatin. Previous research suggested that flies that lack the Bloom syndrome helicase (Blm) lose meiotic crossover patterning, including the centromere effect. Mapping of centromere-proximal crossovers in Blm mutants reveals that the suppression within the HR-heterochromatin is intact, but the distance-dependent centromere effect is lost. We conclude that centromere-proximal crossovers are suppressed by two separable mechanisms: an HR-heterochromatin effect that completely suppresses crossovers in the HR-heterochromatin, and the centromere effect, which suppresses crossovers with a dissipating effect with distance from the centromere.
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Affiliation(s)
- Michaelyn Hartmann
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - James Umbanhowar
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, North Carolina 27599
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, North Carolina 27599
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599
- Integrative Program in Biological and Genome Sciences, University of North Carolina, Chapel Hill, North Carolina 27599
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28
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DNA damage in aging, the stem cell perspective. Hum Genet 2019; 139:309-331. [PMID: 31324975 DOI: 10.1007/s00439-019-02047-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 07/05/2019] [Indexed: 02/07/2023]
Abstract
DNA damage is one of the most consistent cellular process proposed to contribute to aging. The maintenance of genomic and epigenomic integrity is critical for proper function of cells and tissues throughout life, and this homeostasis is under constant strain from both extrinsic and intrinsic insults. Considering the relationship between lifespan and genotoxic burden, it is plausible that the longest-lived cellular populations would face an accumulation of DNA damage over time. Tissue-specific stem cells are multipotent populations residing in localized niches and are responsible for maintaining all lineages of their resident tissue/system throughout life. However, many of these stem cells are impacted by genotoxic stress. Several factors may dictate the specific stem cell population response to DNA damage, including the niche location, life history, and fate decisions after damage accrual. This leads to differential handling of DNA damage in different stem cell compartments. Given the importance of adult stem cells in preserving normal tissue function during an individual's lifetime, DNA damage sensitivity and accumulation in these compartments could have crucial implications for aging. Despite this, more support for direct functional effects driven by accumulated DNA damage in adult stem cell compartments is needed. This review will present current evidence for the accumulation and potential influence of DNA damage in adult tissue-specific stem cells and propose inquiry directions that could benefit individual healthspan.
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Turner K, Lynch C, Rouse H, Vasu V, Griffin DK. Direct Single-Cell Analysis of Human Polar Bodies and Cleavage-Stage Embryos Reveals No Evidence of the Telomere Theory of Reproductive Ageing in Relation to Aneuploidy Generation. Cells 2019; 8:E163. [PMID: 30781491 PMCID: PMC6406255 DOI: 10.3390/cells8020163] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 01/28/2019] [Accepted: 02/13/2019] [Indexed: 01/18/2023] Open
Abstract
Reproductive ageing in women, particularly after the age of 35, is associated with an exponential increase in the proportion of chromosomally abnormal oocytes produced. Several hypotheses have attempted to explain this observation, including the 'limited oocyte pool' hypothesis and the 'two-hit' hypothesis, the latter explaining that a depletion in oocyte quality with age results from the multiple opportune stages for errors to occur in meiosis. Recently however, the telomere theory of reproductive ageing in women has been proposed. This suggests that shortened telomeres in oocytes of women of advanced maternal age render oocytes unable to support fertilization and embryogenesis. Despite a credible rationale for the telomere theory of reproductive ageing in women, very few studies have assessed telomere length directly in human oocytes or preimplantation embryos. Therefore, we directly assessed relative telomere length in first polar bodies and blastomeres from cleavage stage (day 3) embryos. In both cell types we tested the hypothesis that (1) older women have shorter telomeres and (2) chromosomally abnormal (aneuploid) gametes/embryos have shorter telomeres. In all cases, we found no evidence of altered telomere length associated with age-related aneuploidy.
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Affiliation(s)
- Kara Turner
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
| | - Colleen Lynch
- Cooper Genomics Nottingham, Medicity, D6 Building, Thane Road, Nottingham NG90 6BH, UK.
| | - Hannah Rouse
- Cooper Genomics Nottingham, Medicity, D6 Building, Thane Road, Nottingham NG90 6BH, UK.
| | - Vimal Vasu
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
- Department of Child Health, East Kent Hospitals University Foundation NHS Trust, William Harvey Hospital, Ashford TN24 0LZ, UK.
| | - Darren K Griffin
- School of Biosciences, University of Kent, Giles Lane, Canterbury CT2 7NJ, UK.
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Ray A, Oliver TR, Halder P, Pal U, Sarkar S, Dutta S, Ghosh S. Risk of Down syndrome birth: Consanguineous marriage is associated with maternal meiosis-II nondisjunction at younger age and without any detectable recombination error. Am J Med Genet A 2018; 176:2342-2349. [PMID: 30240118 DOI: 10.1002/ajmg.a.40511] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 05/17/2018] [Accepted: 07/26/2018] [Indexed: 01/10/2023]
Abstract
Consanguineous marriage was examined as a risk factor for Down syndrome birth. We genotyped Down syndrome family trios using short tandem repeat markers on 21q-to interpret the parental and meiotic stage of origin of errors as well as to record recombination profile along long arm of chromosome 21. We then compared nonconsanguineous (N = 811) group with-the consanguineous (N =157) marriages. We report for the first time that consanguineous marriage is associated with an increased risk for nondisjunction of chromosome 21 in oocytes-during the second meiotic division. We observed the absence of recombination more frequently in younger mothers in nonconsanguineous meiosis I cases. This was in contrast to an equal distribution of nonrecombinant cases across the age categories in the meiosis I consanguineous group. Moreover, the non-consanguineous group exhibited preferential telomeric recombination in meiosis I error among younger women and centromeric recombination in meiosis II errors in older women. In contrast, the consanguineous group exhibited medially placed recombination events in both meiosis I and meiosis II nondisjunction errors. Additionally, we recorded reduced maternal age at conception in the-consanguineous group. These findings suggest novel risk factors associated that increase the risk of chromosome 21 nondisjunction in the families with consanguinity.
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Affiliation(s)
- Anirban Ray
- Cytogenetics & Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
| | | | - Pinku Halder
- Cytogenetics & Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
| | - Upamanyu Pal
- Cytogenetics & Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
| | - Sumantra Sarkar
- Department of Pediatric Medicine, Institute of Post Graduate Medical Education and Research, Kolkata, West Bengal, India
| | - Supratim Dutta
- Department of Pediatric Medicine, Institute of Post Graduate Medical Education and Research, Kolkata, West Bengal, India
| | - Sujay Ghosh
- Cytogenetics & Genomics Research Unit, Department of Zoology, University of Calcutta, Taraknath-Palit-Siksha-Prangan (Ballygunge Science College Campus), Kolkata, West Bengal, India
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31
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Female Meiosis: Synapsis, Recombination, and Segregation in Drosophila melanogaster. Genetics 2018; 208:875-908. [PMID: 29487146 PMCID: PMC5844340 DOI: 10.1534/genetics.117.300081] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 10/18/2017] [Indexed: 12/11/2022] Open
Abstract
A century of genetic studies of the meiotic process in Drosophila melanogaster females has been greatly augmented by both modern molecular biology and major advances in cytology. These approaches, and the findings they have allowed, are the subject of this review. Specifically, these efforts have revealed that meiotic pairing in Drosophila females is not an extension of somatic pairing, but rather occurs by a poorly understood process during premeiotic mitoses. This process of meiotic pairing requires the function of several components of the synaptonemal complex (SC). When fully assembled, the SC also plays a critical role in maintaining homolog synapsis and in facilitating the maturation of double-strand breaks (DSBs) into mature crossover (CO) events. Considerable progress has been made in elucidating not only the structure, function, and assembly of the SC, but also the proteins that facilitate the formation and repair of DSBs into both COs and noncrossovers (NCOs). The events that control the decision to mature a DSB as either a CO or an NCO, as well as determining which of the two CO pathways (class I or class II) might be employed, are also being characterized by genetic and genomic approaches. These advances allow a reconsideration of meiotic phenomena such as interference and the centromere effect, which were previously described only by genetic studies. In delineating the mechanisms by which the oocyte controls the number and position of COs, it becomes possible to understand the role of CO position in ensuring the proper orientation of homologs on the first meiotic spindle. Studies of bivalent orientation have occurred in the context of numerous investigations into the assembly, structure, and function of the first meiotic spindle. Additionally, studies have examined the mechanisms ensuring the segregation of chromosomes that have failed to undergo crossing over.
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Nandi B, Talluri S, Kumar S, Yenumula C, Gold JS, Prabhala R, Munshi NC, Shammas MA. The roles of homologous recombination and the immune system in the genomic evolution of cancer. ACTA ACUST UNITED AC 2018; 5. [PMID: 30873294 PMCID: PMC6411307 DOI: 10.15761/jts.1000282] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A variety of factors, whether extracellular (mutagens/carcinogens and viruses in the environment, chronic inflammation and radiation associated with the environment and/or electronic devices/machines) and/or intracellular (oxidative metabolites of food, oxidative stress due to inflammation, acid production, replication stress, DNA replication/repair errors, and certain hormones, cytokines, growth factors), pose a constant threat to the genomic integrity of a living cell. However, in the normal cellular environment multiple biological pathways including DNA repair, cell cycle, apoptosis and the immune system work in a precise, regulated (tightly controlled), timely and concerted manner to ensure genomic integrity, stability and proper functioning of a cell. If damage to DNA takes place, it is efficiently and accurately repaired by the DNA repair systems. Homologous recombination (HR) which utilizes either a homologous chromosome (in G1 phase) or a sister chromatid (in G2) as a template to repair the damage, is known to be the most precise repair system. HR in G2 which utilizes a sister chromatid as a template is also called an error free repair system. If DNA damage in a cell is so extensive that it overwhelms the repair system/s, the cell is eliminated by apoptosis. Thus, multiple pathways ensure that genome of a cell is intact and stable. However, constant exposure to DNA damage and/or dysregulation of DNA repair mechanism/s poses a risk of mutation and cancer. Oncogenesis, which seems to be a multistep process, is associated with acquisition of a number of genomic changes that enable a normal cell to progress from benign to malignant transformation. Transformed/cancer cells are recognized and killed by the immune system. However, the ongoing acquisition of new genomic changes enables cancer cells to survive/escape immune attack, evolve into a more aggressive phenotype, and eventually develop resistance to therapy. Although DNA repair (especially the HR) and the immune system play unique roles in preserving genomic integrity of a cell, they can also contribute to DNA damage, genomic instability and oncogenesis. The purpose of this article is to highlight the roles of DNA repair (especially HR) and the immune system in genomic evolution, with special focus on gastrointestinal cancer.
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Affiliation(s)
- B Nandi
- Harvard Medical School and Brigham and Women's Hospital, USA.,Researh Services, VA Healthcare System, West Roxbury, MA, USA
| | - S Talluri
- Harvard (Dana Farber) Cancer Institute, Boston, MA, USA.,Researh Services, VA Healthcare System, West Roxbury, MA, USA
| | - S Kumar
- Harvard (Dana Farber) Cancer Institute, Boston, MA, USA.,Harvard Medical School and Brigham and Women's Hospital, USA
| | - C Yenumula
- Harvard Medical School and Brigham and Women's Hospital, USA.,Researh Services, VA Healthcare System, West Roxbury, MA, USA
| | - J S Gold
- Harvard Medical School and Brigham and Women's Hospital, USA.,Surgery Services, VA Healthcare System, West Roxbury, MA, USA
| | - R Prabhala
- Harvard (Dana Farber) Cancer Institute, Boston, MA, USA.,Researh Services, VA Healthcare System, West Roxbury, MA, USA
| | - N C Munshi
- Harvard (Dana Farber) Cancer Institute, Boston, MA, USA.,Harvard Medical School and Brigham and Women's Hospital, USA.,Researh Services, VA Healthcare System, West Roxbury, MA, USA
| | - M A Shammas
- Harvard (Dana Farber) Cancer Institute, Boston, MA, USA.,Researh Services, VA Healthcare System, West Roxbury, MA, USA
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Saiyed N, Bakshi S, Muthuswamy S, Agarwal S. Young mothers and higher incidence of maternal meiosis-I non- disjunction: Interplay of environmental exposure and genetic alterations during halt phase in trisomy 21. Reprod Toxicol 2018; 79:1-7. [PMID: 29702247 DOI: 10.1016/j.reprotox.2018.04.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 04/16/2018] [Accepted: 04/20/2018] [Indexed: 11/16/2022]
Abstract
Trisomy 21 is a genetic condition caused when chromosomes fail to separate during meiosis. We have studied conventional karyotype and QF-PCR using STR markers with high polymorphism and heterogeneity and the results were analyzed, to determine the paternal and meiotic origin of trisomy 21. This study was conducted using a detailed questionnaire to include: paternal, maternal, clinical and family history for various confounding factors such as age and regional environmental exposures where the parents resided. Out of 120 samples 95% (N = 114) were of maternal origin, including 92% (N = 105) of meiosis 1 errors and 8% (N = 9) meiosis 2 errors. Paternal origin accounted for 5% (N = 6) and were all due to meiosis-I errors. The higher incidence of maternal meiosis-I observed in the present study suggests that human trisomy 21 non-disjunction is a result of multiple factors contributing to the origin of the genetic condition.
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Affiliation(s)
- Nazia Saiyed
- Institute of Science, Nirma University, S.G Highway, Ahmedabad, Gujarat, 382481, India
| | - Sonal Bakshi
- Institute of Science, Nirma University, S.G Highway, Ahmedabad, Gujarat, 382481, India.
| | - Srinivasan Muthuswamy
- Sanjay Gandhi Post Graduate Institute of Medical Sciences, Rae Bareli Road, Lucknow, Uttar Pradesh, 226014, India
| | - Sarita Agarwal
- Sanjay Gandhi Post Graduate Institute of Medical Sciences, Rae Bareli Road, Lucknow, Uttar Pradesh, 226014, India
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34
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Underwood CJ, Choi K, Lambing C, Zhao X, Serra H, Borges F, Simorowski J, Ernst E, Jacob Y, Henderson IR, Martienssen RA. Epigenetic activation of meiotic recombination near Arabidopsis thaliana centromeres via loss of H3K9me2 and non-CG DNA methylation. Genome Res 2018; 28:519-531. [PMID: 29530927 PMCID: PMC5880242 DOI: 10.1101/gr.227116.117] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 01/15/2018] [Indexed: 02/02/2023]
Abstract
Eukaryotic centromeres contain the kinetochore, which connects chromosomes to the spindle allowing segregation. During meiosis, centromeres are suppressed for inter-homolog crossover, as recombination in these regions can cause chromosome missegregation and aneuploidy. Plant centromeres are surrounded by transposon-dense pericentromeric heterochromatin that is epigenetically silenced by histone 3 lysine 9 dimethylation (H3K9me2), and DNA methylation in CG and non-CG sequence contexts. However, the role of these chromatin modifications in control of meiotic recombination in the pericentromeres is not fully understood. Here, we show that disruption of Arabidopsis thaliana H3K9me2 and non-CG DNA methylation pathways, for example, via mutation of the H3K9 methyltransferase genes KYP/SUVH4 SUVH5 SUVH6, or the CHG DNA methyltransferase gene CMT3, increases meiotic recombination in proximity to the centromeres. Using immunocytological detection of MLH1 foci and genotyping by sequencing of recombinant plants, we observe that H3K9me2 and non-CG DNA methylation pathway mutants show increased pericentromeric crossovers. Increased pericentromeric recombination in H3K9me2/non-CG mutants occurs in hybrid and inbred backgrounds and likely involves contributions from both the interfering and noninterfering crossover repair pathways. We also show that meiotic DNA double-strand breaks (DSBs) increase in H3K9me2/non-CG mutants within the pericentromeres, via purification and sequencing of SPO11-1-oligonucleotides. Therefore, H3K9me2 and non-CG DNA methylation exert a repressive effect on both meiotic DSB and crossover formation in plant pericentromeric heterochromatin. Our results may account for selection of enhancer trap Dissociation (Ds) transposons into the CMT3 gene by recombination with proximal transposon launch-pads.
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Affiliation(s)
- Charles J. Underwood
- Howard Hughes Medical Institute, Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA;,Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom
| | - Kyuha Choi
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom
| | - Christophe Lambing
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom
| | - Xiaohui Zhao
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom
| | - Heïdi Serra
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom
| | - Filipe Borges
- Howard Hughes Medical Institute, Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Joe Simorowski
- Howard Hughes Medical Institute, Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Evan Ernst
- Howard Hughes Medical Institute, Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Yannick Jacob
- Howard Hughes Medical Institute, Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Ian R. Henderson
- Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, United Kingdom
| | - Robert A. Martienssen
- Howard Hughes Medical Institute, Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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Loss of Drosophila Mei-41/ATR Alters Meiotic Crossover Patterning. Genetics 2017; 208:579-588. [PMID: 29247012 DOI: 10.1534/genetics.117.300634] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 12/14/2017] [Indexed: 11/18/2022] Open
Abstract
Meiotic crossovers must be properly patterned to ensure accurate disjunction of homologous chromosomes during meiosis I. Disruption of the spatial distribution of crossovers can lead to nondisjunction, aneuploidy, gamete dysfunction, miscarriage, or birth defects. One of the earliest identified genes involved in proper crossover patterning is Drosophila mei-41, which encodes the ortholog of the checkpoint kinase ATR. Analysis of hypomorphic mutants suggested the existence of crossover patterning defects, but it was not possible to assess this in null mutants because of maternal-effect embryonic lethality. To overcome this lethality, we constructed mei-41 null mutants in which we expressed wild-type Mei-41 in the germline after completion of meiotic recombination, allowing progeny to survive. We find that crossovers are decreased to about one-third of wild-type levels, but the reduction is not uniform, being less severe in the proximal regions of chromosome 2L than in medial or distal 2L or on the X chromosome. None of the crossovers formed in the absence of Mei-41 require Mei-9, the presumptive meiotic resolvase, suggesting that Mei-41 functions everywhere, despite the differential effects on crossover frequency. Interference appears to be significantly reduced or absent in mei-41 mutants, but the reduction in crossover density in centromere-proximal regions is largely intact. We propose that crossover patterning is achieved in a stepwise manner, with the crossover suppression related to proximity to the centromere occurring prior to and independently of crossover designation and enforcement of interference. In this model, Mei-41 has an essential function in meiotic recombination after the centromere effect is established but before crossover designation and interference occur.
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Greaney J, Wei Z, Homer H. Regulation of chromosome segregation in oocytes and the cellular basis for female meiotic errors. Hum Reprod Update 2017; 24:135-161. [PMID: 29244163 DOI: 10.1093/humupd/dmx035] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Revised: 09/12/2017] [Accepted: 11/26/2017] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND Meiotic chromosome segregation in human oocytes is notoriously error-prone, especially with ageing. Such errors markedly reduce the reproductive chances of increasing numbers of women embarking on pregnancy later in life. However, understanding the basis for these errors is hampered by limited access to human oocytes. OBJECTIVE AND RATIONALE Important new discoveries have arisen from molecular analyses of human female recombination and aneuploidy along with high-resolution analyses of human oocyte maturation and mouse models. Here, we review these findings to provide a contemporary picture of the key players choreographing chromosome segregation in mammalian oocytes and the cellular basis for errors. SEARCH METHODS A search of PubMed was conducted using keywords including meiosis, oocytes, recombination, cohesion, cohesin complex, chromosome segregation, kinetochores, spindle, aneuploidy, meiotic cell cycle, spindle assembly checkpoint, anaphase-promoting complex, DNA damage, telomeres, mitochondria, female ageing and female fertility. We extracted papers focusing on mouse and human oocytes that best aligned with the themes of this review and that reported transformative and novel discoveries. OUTCOMES Meiosis incorporates two sequential rounds of chromosome segregation executed by a spindle whose component microtubules bind chromosomes via kinetochores. Cohesion mediated by the cohesin complex holds chromosomes together and should be resolved at the appropriate time, in a specific step-wise manner and in conjunction with meiotically programmed kinetochore behaviour. In women, the stage is set for meiotic error even before birth when female-specific crossover maturation inefficiency leads to the formation of at-risk recombination patterns. In adult life, multiple co-conspiring factors interact with at-risk crossovers to increase the likelihood of mis-segregation. Available evidence support that these factors include, but are not limited to, cohesion deterioration, uncoordinated sister kinetochore behaviour, erroneous microtubule attachments, spindle instability and structural chromosomal defects that impact centromeres and telomeres. Data from mice indicate that cohesin and centromere-specific histones are long-lived proteins in oocytes. Since these proteins are pivotal for chromosome segregation, but lack any obvious renewal pathway, their deterioration with age provides an appealing explanation for at least some of the problems in older oocytes. WIDER IMPLICATIONS Research in the mouse model has identified a number of candidate genes and pathways that are important for chromosome segregation in this species. However, many of these have not yet been investigated in human oocytes so it is uncertain at this stage to what extent they apply to women. The challenge for the future involves applying emerging knowledge of female meiotic molecular regulation towards improving clinical fertility management.
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Affiliation(s)
- Jessica Greaney
- Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston QLD 4029, Australia
| | - Zhe Wei
- Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston QLD 4029, Australia
| | - Hayden Homer
- Christopher Chen Oocyte Biology Research Laboratory, Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Royal Brisbane & Women's Hospital Campus, Herston QLD 4029, Australia
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Sachdeva K, Discutido R, Albuz F, Almekosh R, Peramo B. Validation of Next-Generation Sequencer for 24-Chromosome Aneuploidy Screening in Human Embryos. Genet Test Mol Biomarkers 2017; 21:674-680. [PMID: 28885040 DOI: 10.1089/gtmb.2017.0108] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Next-Generation Sequencing (NGS) is the latest approach for preimplantation genetic diagnoses (PGD). AIM The purpose of this study was to standardize and validate an NGS method for comprehensive chromosome screening and to investigate its applicability to PGD. METHODS Embryo biopsy, whole-genome amplification, array comparative genomic hybridization (aCGH), and semiconductor sequencing were employed. RESULTS A total of 204 whole-genome-amplified products were tested with an NGS-based protocol, from which 100 samples were used for standardization and to evaluate the quality of the results produced by this new technique. The remaining 104 samples tested by NGS were previously analyzed by using the aCGH protocol to determine the sensitivity and specificity of this new technique. In total, 4896 chromosomes were assessed, out of which 196 carried a copy number imbalance. NGS sensitivity and specificity for calling aneuploidy was 100%. CONCLUSION This is the first study reporting preclinical validation and accuracy assessment of the Ion Torrent Personal Genome Machine (PGM) NGS-based comprehensive chromosome screening method using blastomeres and blastocysts. The NGS proved to be a robust methodology and is ready for clinical application in reproductive medicine, with the major advantage of low cost and enhanced precision when compared with other technologies used for comprehensive chromosome screening.
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Affiliation(s)
- Kabir Sachdeva
- Reprogenetics GCC, Al Ain Fertility Centre , Al Ain, United Arab of Emirates
| | - Richard Discutido
- Reprogenetics GCC, Al Ain Fertility Centre , Al Ain, United Arab of Emirates
| | - Firas Albuz
- Reprogenetics GCC, Al Ain Fertility Centre , Al Ain, United Arab of Emirates
| | - Rawan Almekosh
- Reprogenetics GCC, Al Ain Fertility Centre , Al Ain, United Arab of Emirates
| | - Braulio Peramo
- Reprogenetics GCC, Al Ain Fertility Centre , Al Ain, United Arab of Emirates
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38
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Hatkevich T, Sekelsky J. Bloom syndrome helicase in meiosis: Pro-crossover functions of an anti-crossover protein. Bioessays 2017; 39. [PMID: 28792069 DOI: 10.1002/bies.201700073] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The functions of the Bloom syndrome helicase (BLM) and its orthologs are well characterized in mitotic DNA damage repair, but their roles within the context of meiotic recombination are less clear. In meiotic recombination, multiple repair pathways are used to repair meiotic DSBs, and current studies suggest that BLM may regulate the use of these pathways. Based on literature from Saccharomyces cerevisiae, Arabidopsis thaliana, Mus musculus, Drosophila melanogaster, and Caenorhabditis elegans, we present a unified model for a critical meiotic role of BLM and its orthologs. In this model, BLM and its orthologs utilize helicase activity to regulate the use of various pathways in meiotic recombination by continuously disassembling recombination intermediates. This unwinding activity provides the meiotic program with a steady pool of early recombination substrates, increasing the probability for a DSB to be processed by the appropriate pathway. As a result of BLM activity, crossovers are properly placed throughout the genome, promoting proper chromosomal disjunction at the end of meiosis. This unified model can be used to further refine the complex role of BLM and its orthologs in meiotic recombination.
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Affiliation(s)
- Talia Hatkevich
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Jeff Sekelsky
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.,Integrative Program in Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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39
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Abstract
The impact of age on a woman's ability to produce normal eggs remains a great enigma of human biology. A new paper provides intriguing experimental evidence that age may cause a breakdown in the egg cell division machinery.
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Affiliation(s)
- Patricia Hunt
- School of Molecular Biosciences and Center for Reproductive Biology, Washington State University, Pullman, WA, USA.
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Meiotic Consequences of Genetic Divergence Across the Murine Pseudoautosomal Region. Genetics 2017; 205:1089-1100. [PMID: 28100589 PMCID: PMC5340325 DOI: 10.1534/genetics.116.189092] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 01/03/2017] [Indexed: 02/07/2023] Open
Abstract
The production of haploid gametes during meiosis is dependent on the homology-driven processes of pairing, synapsis, and recombination. On the mammalian heterogametic sex chromosomes, these key meiotic activities are confined to the pseudoautosomal region (PAR), a short region of near-perfect sequence homology between the X and Y chromosomes. Despite its established importance for meiosis, the PAR is rapidly evolving, raising the question of how proper X/Y segregation is buffered against the accumulation of homology-disrupting mutations. Here, I investigate the interplay of PAR evolution and function in two interfertile house mouse subspecies characterized by structurally divergent PARs, Mus musculus domesticus and M. m. castaneus. Using cytogenetic methods to visualize the sex chromosomes at meiosis, I show that intersubspecific F1 hybrids harbor an increased frequency of pachytene spermatocytes with unsynapsed sex chromosomes. This high rate of asynapsis is due, in part, to the premature release of synaptic associations prior to completion of prophase I. Further, I show that when sex chromosomes do synapse in intersubspecific hybrids, recombination is reduced across the paired region. Together, these meiotic defects afflict ∼50% of spermatocytes from F1 hybrids and lead to increased apoptosis in meiotically dividing cells. Despite flagrant disruption of the meiotic program, a subset of spermatocytes complete meiosis and intersubspecific F1 males remain fertile. These findings cast light on the meiotic constraints that shape sex chromosome evolution and offer initial clues to resolve the paradox raised by the rapid evolution of this functionally significant locus.
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41
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Abstract
The proper distribution of crossovers during meiosis I ensures accurate chromosome segregation at the first meiotic division. A new study reveals both the consequences of improper crossover patterning in Drosophila and the role of Blm helicase in controlling this patterning.
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Reichman R, Alleva B, Smolikove S. Prophase I: Preparing Chromosomes for Segregation in the Developing Oocyte. Results Probl Cell Differ 2017; 59:125-173. [PMID: 28247048 DOI: 10.1007/978-3-319-44820-6_5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Formation of an oocyte involves a specialized cell division termed meiosis. In meiotic prophase I (the initial stage of meiosis), chromosomes undergo elaborate events to ensure the proper segregation of their chromosomes into gametes. These events include processes leading to the formation of a crossover that, along with sister chromatid cohesion, forms the physical link between homologous chromosomes. Crossovers are formed as an outcome of recombination. This process initiates with programmed double-strand breaks that are repaired through the use of homologous chromosomes as a repair template. The accurate repair to form crossovers takes place in the context of the synaptonemal complex, a protein complex that links homologous chromosomes in meiotic prophase I. To allow proper execution of meiotic prophase I events, signaling processes connect different steps in recombination and synapsis. The events occurring in meiotic prophase I are a prerequisite for proper chromosome segregation in the meiotic divisions. When these processes go awry, chromosomes missegregate. These meiotic errors are thought to increase with aging and may contribute to the increase in aneuploidy observed in advanced maternal age female oocytes.
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Affiliation(s)
- Rachel Reichman
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Benjamin Alleva
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Sarit Smolikove
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA.
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Meiotic Centromere Coupling and Pairing Function by Two Separate Mechanisms in Saccharomyces cerevisiae. Genetics 2016; 205:657-671. [PMID: 27913618 DOI: 10.1534/genetics.116.190264] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 11/25/2016] [Indexed: 12/17/2022] Open
Abstract
In meiosis I, chromosomes become paired with their homologous partners and then are pulled toward opposite poles of the spindle. In the budding yeast, Saccharomyces cerevisiae, in early meiotic prophase, centromeres are observed to associate in pairs in a homology-independent manner; a process called centromere coupling. Later, as homologous chromosomes align, their centromeres associate in a process called centromere pairing. The synaptonemal complex protein Zip1 is necessary for both types of centromere association. We aimed to test the role of centromere coupling in modulating recombination at centromeres, and to test whether the two types of centromere associations depend upon the same sets of genes. The zip1-S75E mutation, which blocks centromere coupling but no other known functions of Zip1, was used to show that in the absence of centromere coupling, centromere-proximal recombination was unchanged. Further, this mutation did not diminish centromere pairing, demonstrating that these two processes have different genetic requirements. In addition, we tested other synaptonemal complex components, Ecm11 and Zip4, for their contributions to centromere pairing. ECM11 was dispensable for centromere pairing and segregation of achiasmate partner chromosomes; while ZIP4 was not required for centromere pairing during pachytene, but was required for proper segregation of achiasmate chromosomes. These findings help differentiate the two mechanisms that allow centromeres to interact in meiotic prophase, and illustrate that centromere pairing, which was previously shown to be necessary to ensure disjunction of achiasmate chromosomes, is not sufficient for ensuring their disjunction.
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Oxidative stress in oocytes during midprophase induces premature loss of cohesion and chromosome segregation errors. Proc Natl Acad Sci U S A 2016; 113:E6823-E6830. [PMID: 27791141 DOI: 10.1073/pnas.1612047113] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
In humans, errors in meiotic chromosome segregation that produce aneuploid gametes increase dramatically as women age, a phenomenon termed the "maternal age effect." During meiosis, cohesion between sister chromatids keeps recombinant homologs physically attached and premature loss of cohesion can lead to missegregation of homologs during meiosis I. A growing body of evidence suggests that meiotic cohesion deteriorates as oocytes age and contributes to the maternal age effect. One hallmark of aging cells is an increase in oxidative damage caused by reactive oxygen species (ROS). Therefore, increased oxidative damage in older oocytes may be one of the factors that leads to premature loss of cohesion and segregation errors. To test this hypothesis, we used an RNAi strategy to induce oxidative stress in Drosophila oocytes and measured the fidelity of chromosome segregation during meiosis. Knockdown of either the cytoplasmic or mitochondrial ROS scavenger superoxide dismutase (SOD) caused a significant increase in segregation errors, and heterozygosity for an smc1 deletion enhanced this phenotype. FISH analysis indicated that SOD knockdown moderately increased the percentage of oocytes with arm cohesion defects. Consistent with premature loss of arm cohesion and destabilization of chiasmata, the frequency at which recombinant homologs missegregate during meiosis I is significantly greater in SOD knockdown oocytes than in controls. Together these results provide an in vivo demonstration that oxidative stress during meiotic prophase induces chromosome segregation errors and support the model that accelerated loss of cohesion in aging human oocytes is caused, at least in part, by oxidative damage.
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Jaiswal SK, Sukla KK, Chauhan A, Lakhotia AR, Kumar A, Rai AK. Choline metabolic pathway gene polymorphisms and risk for Down syndrome: An association study in a population with folate-homocysteine metabolic impairment. Eur J Clin Nutr 2016; 71:45-50. [PMID: 27677362 DOI: 10.1038/ejcn.2016.190] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 08/23/2016] [Accepted: 08/26/2016] [Indexed: 12/19/2022]
Abstract
BACKGROUND/OBJECTIVES Choline is an essential nutrient involved in one-carbon metabolism, but its role in mechanisms underlying meiotic non-disjunction is poorly known. The relationship between folate-homocysteine metabolic pathway gene polymorphism and Down syndrome (DS) risk has been widely analyzed, but there are limited reports on its correlation with choline metabolism. In the present case-control association study, we investigated the relationship of three single-nucleotide polymorphisms (SNPs) (phosphatidylethanolamine N-methyltransferase (PEMT) rs12325817, choline dehydrogenase (CHDH) rs12676 and homocysteine methyltransferase (BHMT) rs3733890) of choline metabolism with risk for DS. SUBJECT/METHODS Genotyping of 228 mothers of a down syndrome child (DSM) and 200 control mothers (CMs) for all SNPs was performed by PCR coupled with restriction fragment length polymorphism method. RESULTS A significantly increased risk for BHMT +742AA genotype with an odds ratio of 4.96 (95% confidence interval (CI): 1.66-14.88, P=0.0036) was observed. For PEMT rs12325817 and CHDH rs12676, no significant difference in allelic and genotypic frequencies was observed. In genotypic combination analysis considering PEMT -744GG/CHDH +432GG/BHMT +742GG as the reference combination, PEMT -744GC/CHDH +432GG/BHMT +742GG genotypic combination was significantly higher in DSM compared with that in CMs with an odds ratio of 2.061 (95% CI: 1.10-3.86, P=0.0342). We also observed an epistatic interaction between methylenetetrahydrofolate reductase (MTHFR) rs1801133 and choline metabolic pathway gene variants. CONCLUSIONS Our findings indicate impaired choline metabolism showing a greater risk for DS, especially in a population associated with homocysteine-folate impairment. Further studies are required to confirm our findings.
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Affiliation(s)
- S K Jaiswal
- Centre for Genetic Disorders, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - K K Sukla
- Cytogenetics Laboratory, Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - A Chauhan
- Applied Microbiology, Department of Botany, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - A R Lakhotia
- Department of Gynecology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - A Kumar
- Department of Pediatrics, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | - A K Rai
- Centre for Genetic Disorders, Banaras Hindu University, Varanasi, Uttar Pradesh, India
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46
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Jagut M, Hamminger P, Woglar A, Millonigg S, Paulin L, Mikl M, Dello Stritto MR, Tang L, Habacher C, Tam A, Gallach M, von Haeseler A, Villeneuve AM, Jantsch V. Separable Roles for a Caenorhabditis elegans RMI1 Homolog in Promoting and Antagonizing Meiotic Crossovers Ensure Faithful Chromosome Inheritance. PLoS Biol 2016; 14:e1002412. [PMID: 27011106 PMCID: PMC4807110 DOI: 10.1371/journal.pbio.1002412] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 02/19/2016] [Indexed: 11/30/2022] Open
Abstract
During the first meiotic division, crossovers (COs) between homologous chromosomes ensure their correct segregation. COs are produced by homologous recombination (HR)-mediated repair of programmed DNA double strand breaks (DSBs). As more DSBs are induced than COs, mechanisms are required to establish a regulated number of COs and to repair remaining intermediates as non-crossovers (NCOs). We show that the Caenorhabditis elegans RMI1 homolog-1 (RMH-1) functions during meiosis to promote both CO and NCO HR at appropriate chromosomal sites. RMH-1 accumulates at CO sites, dependent on known pro-CO factors, and acts to promote CO designation and enforce the CO outcome of HR-intermediate resolution. RMH-1 also localizes at NCO sites and functions in parallel with SMC-5 to antagonize excess HR-based connections between chromosomes. Moreover, RMH-1 also has a major role in channeling DSBs into an NCO HR outcome near the centers of chromosomes, thereby ensuring that COs form predominantly at off-center positions. A nematode homolog of the conserved DNA repair factor RMI1 plays multiple genetically separable roles that together ensure the faithful inheritance of intact genomes during sexual reproduction. During meiosis, faithful separation of chromosomes into gametes is essential for fertility and healthy progeny. During the first meiotic division, crossovers (CO) between parental homologs ensure their correct segregation. Programmed DNA double strand breaks (DSBs) and resection steps generate single-stranded overhangs that invade a sister chromatid of the homolog to initiate homologous recombination. This culminates in the generation of a DNA double Holliday junction (dHJ). This can be acted upon by resolvases to produce CO and non-crossover (NCO) products, depending on where the resolvases cut the DNA. Alternatively, NCOs can also be produced by decatenation via the RecQ helicase–topoisomeraseIII–Rmi1 (RTR) complex. The mammalian RTR contains a topoisomerase, Bloom’s helicase, and RMI1/2 scaffolding components. It disassembles dHJs in vitro and contributes the major NCO activity in mitosis. Here, we provide evidence that the Caenorhabditis elegans RMH-1 functions in distinct complexes during meiosis to produce both COs and NCOs in an in vivo animal model system. Strikingly, RMH-1 spatially regulates the distribution of COs on chromosomes, demonstrating that the RTR complex can act locally within specific chromosome domains.
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Affiliation(s)
- Marlène Jagut
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Patricia Hamminger
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Alexander Woglar
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
- Departments of Developmental Biology and Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Sophia Millonigg
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Luis Paulin
- Center for Integrative Bioinformatics Vienna (CIBIV), Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Martin Mikl
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Maria Rosaria Dello Stritto
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Lois Tang
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Cornelia Habacher
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
| | - Angela Tam
- Departments of Developmental Biology and Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Miguel Gallach
- Center for Integrative Bioinformatics Vienna (CIBIV), Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Arndt von Haeseler
- Center for Integrative Bioinformatics Vienna (CIBIV), Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna and Medical University of Vienna, Vienna, Austria
- Bioinformatics and Computational Biology, Faculty of Computer Science, University of Vienna, Austria
| | - Anne M. Villeneuve
- Departments of Developmental Biology and Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Verena Jantsch
- Department of Chromosome Biology, Max F. Perutz Laboratories, Vienna Bio Center, University of Vienna, Vienna, Austria
- * E-mail:
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47
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Nambiar M, Smith GR. Repression of harmful meiotic recombination in centromeric regions. Semin Cell Dev Biol 2016; 54:188-97. [PMID: 26849908 DOI: 10.1016/j.semcdb.2016.01.042] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 01/27/2016] [Indexed: 11/16/2022]
Abstract
During the first division of meiosis, segregation of homologous chromosomes reduces the chromosome number by half. In most species, sister chromatid cohesion and reciprocal recombination (crossing-over) between homologous chromosomes are essential to provide tension to signal proper chromosome segregation during the first meiotic division. Crossovers are not distributed uniformly throughout the genome and are repressed at and near the centromeres. Rare crossovers that occur too near or in the centromere interfere with proper segregation and can give rise to aneuploid progeny, which can be severely defective or inviable. We review here how crossing-over occurs and how it is prevented in and around the centromeres. Molecular mechanisms of centromeric repression are only now being elucidated. However, rapid advances in understanding crossing-over, chromosome structure, and centromere functions promise to explain how potentially deleterious crossovers are avoided in certain chromosomal regions while allowing beneficial crossovers in others.
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Affiliation(s)
- Mridula Nambiar
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA, United States.
| | - Gerald R Smith
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA, United States.
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Termolino P, Cremona G, Consiglio MF, Conicella C. Insights into epigenetic landscape of recombination-free regions. Chromosoma 2016; 125:301-8. [PMID: 26801812 PMCID: PMC4830869 DOI: 10.1007/s00412-016-0574-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 01/10/2016] [Accepted: 01/12/2016] [Indexed: 11/29/2022]
Abstract
Genome architecture is shaped by gene-rich and repeat-rich regions also known as euchromatin and heterochromatin, respectively. Under normal conditions, the repeat-containing regions undergo little or no meiotic crossover (CO) recombination. COs within repeats are risky for the genome integrity. Indeed, they can promote non-allelic homologous recombination (NAHR) resulting in deleterious genomic rearrangements associated with diseases in humans. The assembly of heterochromatin is driven by the combinatorial action of many factors including histones, their modifications, and DNA methylation. In this review, we discuss current knowledge dealing with the epigenetic signatures of the major repeat regions where COs are suppressed. Then we describe mutants for epiregulators of heterochromatin in different organisms to find out how chromatin structure influences the CO rate and distribution.
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Affiliation(s)
- Pasquale Termolino
- CNR, National Research Council of Italy, Institute of Biosciences and Bioresources, Research Division Portici, Via Università 133, 80055, Portici, Italy
| | - Gaetana Cremona
- CNR, National Research Council of Italy, Institute of Biosciences and Bioresources, Research Division Portici, Via Università 133, 80055, Portici, Italy
| | - Maria Federica Consiglio
- CNR, National Research Council of Italy, Institute of Biosciences and Bioresources, Research Division Portici, Via Università 133, 80055, Portici, Italy
| | - Clara Conicella
- CNR, National Research Council of Italy, Institute of Biosciences and Bioresources, Research Division Portici, Via Università 133, 80055, Portici, Italy.
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49
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Gruhn J, Al-Asmar N, Fasnacht R, Maylor-Hagen H, Peinado V, Rubio C, Broman K, Hunt P, Hassold T. Correlations between Synaptic Initiation and Meiotic Recombination: A Study of Humans and Mice. Am J Hum Genet 2016; 98:102-15. [PMID: 26749305 DOI: 10.1016/j.ajhg.2015.11.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 11/16/2015] [Indexed: 10/22/2022] Open
Abstract
Meiotic recombination is initiated by programmed double strand breaks (DSBs), only a small subset of which are resolved into crossovers (COs). The mechanism determining the location of these COs is not well understood. Studies in plants, fungi, and insects indicate that the same genomic regions are involved in synaptic initiation and COs, suggesting that early homolog alignment is correlated with the eventual resolution of DSBs as COs. It is generally assumed that this relationship extends to mammals, but little effort has been made to test this idea. Accordingly, we conducted an analysis of synaptic initiation sites (SISs) and COs in human and mouse spermatocytes and oocytes. In contrast to our expectation, we observed remarkable sex- and species-specific differences, including pronounced differences between human males and females in both the number and chromosomal location of SISs. Further, the combined data from our studies in mice and humans suggest that the relationship between SISs and COs in mammals is a complex one that is not dictated by the sites of synaptic initiation as reported in other organisms, although it is clearly influenced by them.
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50
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Kotdawala A, Patel D, Herrero J, Khajuria R, Mahajan N, Banker M. Aneuploidy screening by array comparative genomic hybridization improves success rates of in vitro fertilization: A multicenter Indian study. J Hum Reprod Sci 2016; 9:223-229. [PMID: 28216909 PMCID: PMC5296825 DOI: 10.4103/0974-1208.197630] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE: To evaluate the usefulness of preimplantation genetic screening (PGS) using array comparative genomic hybridization (aCGH) in the Indian population. MATERIALS AND METHODS: This is a retrospective, multicenter study including 235 PGS cycles following intracytoplasmic sperm injection performed at six different infertility centers from September 2013 to June 2015. Patients were divided as per maternal age in several groups (<35, 35–36, 37–38, 39–40, and >40 years) and as per indication for undergoing PGS. Indications for performing PGS were recurrent miscarriage, repetitive implantation failure, severe male factor, previous trisomic pregnancy, and advanced maternal age (≥35). Day 3 embryo biopsy was performed and analyzed by aCGH followed by day 5 embryo transfer in the same cycle or the following cycle. Outcomes such as pregnancy rates (PRs)/transfer, implantation rates, miscarriage rates, percentage of abnormal embryos, and number of embryos with more than one aneuploidy and chaotic patterns were recorded for all the treated subjects based on different age and indication groups. RESULTS: aCGH helped in identifying aneuploid embryos, thus leading to consistent implantation (range: 33.3%–42.9%) and PRs per transfer (range: 31.8%–54.9%) that were obtained for all the indications in all the age groups, after performing PGS. CONCLUSION: Aneuploidy is one of the major factors which affect embryo implantation. aCGH can be successfully employed for screening of aneuploid embryos. When euploid embryos are transferred, an increase in PRs can be achieved irrespective of the age or the indication.
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Affiliation(s)
| | - Deven Patel
- Nova IVI Fertility, Ahmedabad, Gujarat, India
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