1
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Toraason E, Salagean A, Almanzar DE, Brown JE, Richter CM, Kurhanewicz NA, Rog O, Libuda DE. BRCA1/BRC-1 and SMC-5/6 regulate DNA repair pathway engagement during Caenorhabditis elegans meiosis. eLife 2024; 13:e80687. [PMID: 39115289 PMCID: PMC11368404 DOI: 10.7554/elife.80687] [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: 05/31/2022] [Accepted: 08/07/2024] [Indexed: 09/03/2024] Open
Abstract
The preservation of genome integrity during sperm and egg development is vital for reproductive success. During meiosis, the tumor suppressor BRCA1/BRC-1 and structural maintenance of chromosomes 5/6 (SMC-5/6) complex genetically interact to promote high fidelity DNA double strand break (DSB) repair, but the specific DSB repair outcomes these proteins regulate remain unknown. Using genetic and cytological methods to monitor resolution of DSBs with different repair partners in Caenorhabditis elegans, we demonstrate that both BRC-1 and SMC-5 repress intersister crossover recombination events. Sequencing analysis of conversion tracts from homolog-independent DSB repair events further indicates that BRC-1 regulates intersister/intrachromatid noncrossover conversion tract length. Moreover, we find that BRC-1 specifically inhibits error prone repair of DSBs induced at mid-pachytene. Finally, we reveal functional interactions of BRC-1 and SMC-5/6 in regulating repair pathway engagement: BRC-1 is required for localization of recombinase proteins to DSBs in smc-5 mutants and enhances DSB repair defects in smc-5 mutants by repressing theta-mediated end joining (TMEJ). These results are consistent with a model in which some functions of BRC-1 act upstream of SMC-5/6 to promote recombination and inhibit error-prone DSB repair, while SMC-5/6 acts downstream of BRC-1 to regulate the formation or resolution of recombination intermediates. Taken together, our study illuminates the coordinated interplay of BRC-1 and SMC-5/6 to regulate DSB repair outcomes in the germline.
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Affiliation(s)
- Erik Toraason
- Institute of Molecular Biology, Department of Biology, University of OregonEugeneUnited States
| | - Alina Salagean
- Institute of Molecular Biology, Department of Biology, University of OregonEugeneUnited States
| | - David E Almanzar
- School of Biological Sciences and Center for Cell and Genome Sciences, University of UtahSalt Lake CityUnited States
| | - Jordan E Brown
- Institute of Molecular Biology, Department of Biology, University of OregonEugeneUnited States
| | - Colette M Richter
- Institute of Molecular Biology, Department of Biology, University of OregonEugeneUnited States
| | - Nicole A Kurhanewicz
- Institute of Molecular Biology, Department of Biology, University of OregonEugeneUnited States
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of UtahSalt Lake CityUnited States
| | - Diana E Libuda
- Institute of Molecular Biology, Department of Biology, University of OregonEugeneUnited States
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2
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Hernández Sánchez-Rebato M, Schubert V, White CI. Meiotic double-strand break repair DNA synthesis tracts in Arabidopsis thaliana. PLoS Genet 2024; 20:e1011197. [PMID: 39012914 PMCID: PMC11280534 DOI: 10.1371/journal.pgen.1011197] [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: 02/25/2024] [Revised: 07/26/2024] [Accepted: 06/27/2024] [Indexed: 07/18/2024] Open
Abstract
We report here the successful labelling of meiotic prophase I DNA synthesis in the flowering plant, Arabidopsis thaliana. Incorporation of the thymidine analogue, EdU, enables visualisation of the footprints of recombinational repair of programmed meiotic DNA double-strand breaks (DSB), with ~400 discrete, SPO11-dependent, EdU-labelled chromosomal foci clearly visible at pachytene and later stages of meiosis. This number equates well with previous estimations of 200-300 DNA double-strand breaks per meiosis in Arabidopsis, confirming the power of this approach to detect the repair of most or all SPO11-dependent meiotic DSB repair events. The chromosomal distribution of these DNA-synthesis foci accords with that of early recombination markers and MLH1, which marks Class I crossover sites. Approximately 10 inter-homologue cross-overs (CO) have been shown to occur in each Arabidopsis male meiosis and, athough very probably under-estimated, an equivalent number of inter-homologue gene conversions (GC) have been described. Thus, at least 90% of meiotic recombination events, and very probably more, have not previously been accessible for analysis. Visual examination of the patterns of the foci on the synapsed pachytene chromosomes corresponds well with expectations from the different mechanisms of meiotic recombination and notably, no evidence for long Break-Induced Replication DNA synthesis tracts was found. Labelling of meiotic prophase I, SPO11-dependent DNA synthesis holds great promise for further understanding of the molecular mechanisms of meiotic recombination, at the heart of reproduction and evolution of eukaryotes.
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Affiliation(s)
- Miguel Hernández Sánchez-Rebato
- Institut de Génétique, Reproduction et Développement, CNRS UMR 6293, INSERM U1103, Université Clermont Auvergne, Clermont-Ferrand, France
| | - Veit Schubert
- Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, Seeland, Germany
| | - Charles I. White
- Institut de Génétique, Reproduction et Développement, CNRS UMR 6293, INSERM U1103, Université Clermont Auvergne, Clermont-Ferrand, France
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3
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Abstract
The raison d'être of meiosis is shuffling of genetic information via Mendelian segregation and, within individual chromosomes, by DNA crossing-over. These outcomes are enabled by a complex cellular program in which interactions between homologous chromosomes play a central role. We first provide a background regarding the basic principles of this program. We then summarize the current understanding of the DNA events of recombination and of three processes that involve whole chromosomes: homolog pairing, crossover interference, and chiasma maturation. All of these processes are implemented by direct physical interaction of recombination complexes with underlying chromosome structures. Finally, we present convergent lines of evidence that the meiotic program may have evolved by coupling of this interaction to late-stage mitotic chromosome morphogenesis.
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Affiliation(s)
- Denise Zickler
- Institute for Integrative Biology of the Cell (I2BC), Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Nancy Kleckner
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA;
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4
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Lu L, Abbott AL. Male gonad-enriched microRNAs function to control sperm production in C. elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.10.561762. [PMID: 37873419 PMCID: PMC10592766 DOI: 10.1101/2023.10.10.561762] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Germ cell development and gamete production in animals require small RNA pathways. While studies indicate that microRNAs (miRNAs) are necessary for normal sperm production and function, the specific roles for individual miRNAs are largely unknown. Here, we use small RNA sequencing of dissected gonads and functional analysis of new loss of function alleles to identify functions for miRNAs in the control of fecundity and sperm production in Caenorhabditis elegans males and hermaphrodites. We describe a set of 29 male gonad-enriched miRNAs and identify a set of 3 individual miRNAs (mir-58.1, mir-83, and mir-235) and a miRNA cluster (mir-4807-4810.1) that are required for optimal sperm production at 20°C and 5 additional miRNAs (mir-49, mir-57, mir-261, and mir-357/358) that are required for sperm production at 25°C. We observed defects in meiotic progression in mir-58.1, mir-83, mir-235, and mir-4807-4810.1 mutants that may contribute to the reduced number of sperm. Further, analysis of multiple mutants of these miRNAs suggested complex genetic interactions between these miRNAs for sperm production. This study provides insights on the regulatory roles of miRNAs that promote optimal sperm production and fecundity in males and hermaphrodites.
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Affiliation(s)
- Lu Lu
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201 USA
| | - Allison L. Abbott
- Department of Biological Sciences, Marquette University, Milwaukee, WI, 53201 USA
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5
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Castellano-Pozo M, Sioutas G, Barroso C, Prince JP, Lopez-Jimenez P, Davy J, Jaso-Tamame AL, Crawley O, Shao N, Page J, Martinez-Perez E. The kleisin subunit controls the function of C. elegans meiotic cohesins by determining the mode of DNA binding and differential regulation by SCC-2 and WAPL-1. eLife 2023; 12:e84138. [PMID: 37650378 PMCID: PMC10497282 DOI: 10.7554/elife.84138] [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: 10/12/2022] [Accepted: 07/29/2023] [Indexed: 09/01/2023] Open
Abstract
The cohesin complex plays essential roles in chromosome segregation, 3D genome organisation, and DNA damage repair through its ability to modify DNA topology. In higher eukaryotes, meiotic chromosome function, and therefore fertility, requires cohesin complexes containing meiosis-specific kleisin subunits: REC8 and RAD21L in mammals and REC-8 and COH-3/4 in Caenorhabditis elegans. How these complexes perform the multiple functions of cohesin during meiosis and whether this involves different modes of DNA binding or dynamic association with chromosomes is poorly understood. Combining time-resolved methods of protein removal with live imaging and exploiting the temporospatial organisation of the C. elegans germline, we show that REC-8 complexes provide sister chromatid cohesion (SCC) and DNA repair, while COH-3/4 complexes control higher-order chromosome structure. High-abundance COH-3/4 complexes associate dynamically with individual chromatids in a manner dependent on cohesin loading (SCC-2) and removal (WAPL-1) factors. In contrast, low-abundance REC-8 complexes associate stably with chromosomes, tethering sister chromatids from S-phase until the meiotic divisions. Our results reveal that kleisin identity determines the function of meiotic cohesin by controlling the mode and regulation of cohesin-DNA association, and are consistent with a model in which SCC and DNA looping are performed by variant cohesin complexes that coexist on chromosomes.
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Affiliation(s)
| | | | | | - Josh P Prince
- MRC London Institute of Medical SciencesLondonUnited Kingdom
| | | | - Joseph Davy
- MRC London Institute of Medical SciencesLondonUnited Kingdom
| | | | - Oliver Crawley
- MRC London Institute of Medical SciencesLondonUnited Kingdom
| | - Nan Shao
- MRC London Institute of Medical SciencesLondonUnited Kingdom
| | - Jesus Page
- Universidad Autónoma de MadridMadridSpain
| | - Enrique Martinez-Perez
- MRC London Institute of Medical SciencesLondonUnited Kingdom
- Imperial College Faculty of MedicineLondonUnited Kingdom
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6
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Blanc C, Saclier N, Le Faou E, Marie-Orleach L, Wenger E, Diblasi C, Glemin S, Galtier N, Delattre M. Cosegregation of recombinant chromatids maintains genome-wide heterozygosity in an asexual nematode. SCIENCE ADVANCES 2023; 9:eadi2804. [PMID: 37624896 PMCID: PMC10456839 DOI: 10.1126/sciadv.adi2804] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 07/27/2023] [Indexed: 08/27/2023]
Abstract
In asexual animals, female meiosis is modified to produce diploid oocytes. If meiosis still involves recombination, this is expected to lead to a rapid loss of heterozygosity, with adverse effects on fitness. Many asexuals, however, have a heterozygous genome, the underlying mechanisms being most often unknown. Cytological and population genomic analyses in the nematode Mesorhabditis belari revealed another case of recombining asexual being highly heterozygous genome-wide. We demonstrated that heterozygosity is maintained despite recombination because the recombinant chromatids of each chromosome pair cosegregate during the unique meiotic division. A theoretical model confirmed that this segregation bias is necessary to account for the observed pattern and likely to evolve under a wide range of conditions. Our study uncovers an unexpected type of non-Mendelian genetic inheritance involving cosegregation of recombinant chromatids.
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Affiliation(s)
- Caroline Blanc
- Laboratory of Biology and Modeling of the Cell, Ecole Normale Supérieure de Lyon, CNRS UMR 5239, Inserm U1293, University Claude Bernard Lyon 1, Lyon, France
| | - Nathanaelle Saclier
- Institut des Sciences de l'Evolution, Université Montpellier, Institut de Recherche pour le Développement, 34090 Montpellier, France
| | - Ehouarn Le Faou
- University of Rennes, CNRS, ECOBIO (Ecologie, Biodiversité, Evolution)–UMR 6553, F-35000 Rennes, France
| | - Lucas Marie-Orleach
- University of Rennes, CNRS, ECOBIO (Ecologie, Biodiversité, Evolution)–UMR 6553, F-35000 Rennes, France
| | - Eva Wenger
- Laboratory of Biology and Modeling of the Cell, Ecole Normale Supérieure de Lyon, CNRS UMR 5239, Inserm U1293, University Claude Bernard Lyon 1, Lyon, France
| | - Celian Diblasi
- Institut des Sciences de l'Evolution, Université Montpellier, Institut de Recherche pour le Développement, 34090 Montpellier, France
| | - Sylvain Glemin
- University of Rennes, CNRS, ECOBIO (Ecologie, Biodiversité, Evolution)–UMR 6553, F-35000 Rennes, France
- Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, 75236 Uppsala, Sweden
| | - Nicolas Galtier
- Institut des Sciences de l'Evolution, Université Montpellier, Institut de Recherche pour le Développement, 34090 Montpellier, France
| | - Marie Delattre
- Laboratory of Biology and Modeling of the Cell, Ecole Normale Supérieure de Lyon, CNRS UMR 5239, Inserm U1293, University Claude Bernard Lyon 1, Lyon, France
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7
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Almanzar DE, Gordon SG, Bristow C, Hamrick A, von Diezmann L, Liu H, Rog O. Meiotic DNA exchanges in C. elegans are promoted by proximity to the synaptonemal complex. Life Sci Alliance 2023; 6:e202301906. [PMID: 36697255 PMCID: PMC9877436 DOI: 10.26508/lsa.202301906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Revised: 01/10/2023] [Accepted: 01/11/2023] [Indexed: 01/27/2023] Open
Abstract
During meiosis, programmed double-strand DNA breaks are repaired to form exchanges between the parental chromosomes called crossovers. Chromosomes lacking a crossover fail to segregate accurately into the gametes, leading to aneuploidy. In addition to engaging the homolog, crossover formation requires the promotion of exchanges, rather than non-exchanges, as repair products. However, the mechanism underlying this meiosis-specific preference is not fully understood. Here, we study the regulation of meiotic sister chromatid exchanges in Caenorhabditis elegans by direct visualization. We find that a conserved chromosomal interface that promotes exchanges between the parental chromosomes, the synaptonemal complex, can also promote exchanges between the sister chromatids. In both cases, exchanges depend on the recruitment of the same set of pro-exchange factors to repair sites. Surprisingly, although the synaptonemal complex usually assembles between the two DNA molecules undergoing an exchange, its activity does not rely on a specific chromosome conformation. This suggests that the synaptonemal complex regulates exchanges-both crossovers and sister exchanges-by establishing a nuclear domain conducive to nearby recruitment of exchange-promoting factors.
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Affiliation(s)
- David E Almanzar
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
| | - Spencer G Gordon
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
| | - Chloe Bristow
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
| | - Antonia Hamrick
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
| | - Lexy von Diezmann
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
| | - Hanwenheng Liu
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT, USA
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8
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Mouse oocytes carrying metacentric Robertsonian chromosomes have fewer crossover sites and higher aneuploidy rates than oocytes carrying acrocentric chromosomes alone. Sci Rep 2022; 12:12028. [PMID: 35835815 PMCID: PMC9283534 DOI: 10.1038/s41598-022-16175-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Accepted: 07/06/2022] [Indexed: 12/03/2022] Open
Abstract
Meiotic homologous recombination during fetal development dictates proper chromosome segregation in adult mammalian oocytes. Successful homologous synapsis and recombination during Meiotic Prophase I (MPI) depends on telomere-led chromosome movement along the nuclear envelope. In mice, all chromosomes are acrocentric, while other mammalian species carry a mixture of acrocentric and metacentric chromosomes. Such differences in telomeric structures may explain the exceptionally low aneuploidy rates in mice. Here, we tested whether the presence of metacentric chromosomes carrying Robertsonian translocations (RbT) affects the rate of homologous recombination or aneuploidy. We found a delay in MPI progression in RbT-carrier vs. wild-type (WT) fetal ovaries. Furthermore, resolution of distal telomere clusters, associated with synapsis initiation, was delayed and centromeric telomere clusters persisted until later MPI substages in RbT-carrier oocytes compared to WT oocytes. When chromosomes fully synapsed, higher percentages of RbT-carrier oocytes harbored at least one chromosome pair lacking MLH1 foci, which indicate crossover sites, compared to WT oocytes. Aneuploidy rates in ovulated eggs were also higher in RbT-carrier females than in WT females. In conclusion, the presence of metacentric chromosomes among acrocentric chromosomes in mouse oocytes delays MPI progression and reduces the efficiency of homologous crossover, resulting in a higher frequency of aneuploidy.
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9
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Almanzar DE, Hamrick A, Rog O. Single-sister labeling in the C. elegans germline using the nucleotide analog EdU. STAR Protoc 2022; 3:101344. [PMID: 35509971 PMCID: PMC9059099 DOI: 10.1016/j.xpro.2022.101344] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Reciprocal exchanges between genetically identical sister chromatids (sister chromatid exchanges or SCEs) have been challenging to study. Here, we describe a protocol that utilizes a pulse/chase of the thymidine analog 5-ethyl-3′-deoxyuridine (EdU) in combination with click chemistry and antibody labeling to selectively label sister chromatids in the C. elegans germline. Labeling has no discernable effects on meiosis, allowing for cytological quantification of SCEs. This protocol can be combined with a variety of imaging approaches, including STED, confocal and super-resolution. For complete details on the use and execution of this protocol, please refer to Almanzar et al. (2021). Pulse/chase labeling of individual sister chromatids in the C. elegans germline Can be readily combined with immunofluorescence or other labeling techniques Wide fluorophore support suited for confocal, STED and super-resolution imaging ima Variable chase times allows visualization of single sisters throughout meiosis
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Affiliation(s)
- David E Almanzar
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Antonia Hamrick
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT 84112, USA
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10
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Gasic S, Mihola O, Trachtulec Z. Prdm9 deficiency of rat oocytes causes synapsis among non-homologous chromosomes and aneuploidy. Mamm Genome 2022; 33:590-605. [PMID: 35596034 DOI: 10.1007/s00335-022-09954-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 04/28/2022] [Indexed: 10/18/2022]
Abstract
Aneuploidy (abnormal chromosome number) accompanies reduced ovarian function in humans and mice, but the reasons behind this concomitance remain underexplored. Some variants in the human gene encoding histone-3-lysine-4,36-trimethyltransferase PRDM9 are associated with aneuploidy, and other variants with ovarian function reduced by premature ovarian failure (POF), but no link between POF and aneuploidy has been revealed. SHR/OlaIpcv rat females lacking PRDM9 manifest POF-a reduced follicle number, litter size, and reproductive age. Here, we explored this model to test how POF relates to oocyte euploidy. The mutant rat females displayed increased oocyte aneuploidy and embryonic death of their offspring compared to controls. Because rat PRDM9 positions meiotic DNA breaks, we investigated the repair of these breaks. Fertile control rodents carry pachytene oocytes with synapsed homologous chromosomes and repaired breaks, while sterile Prdm9-deficient mice carry pachytene-like oocytes with many persisting breaks and asynapsed chromosomes. However, most PRDM9-lacking rat oocytes displayed a few persisting breaks and non-homologous synapsis (NHS). HORMAD2 protein serves as a barrier to sister-chromatid repair and a signal for the synapsis and DNA repair checkpoints. NHS but not asynapsis was associated with HORMAD2 levels similar to the levels on rat pachytene chromosomes with homologous synapsis. NHS was accompanied by crossing-over decreased below the minimum that is essential for euploidy. We argue that the increased mutant rat aneuploidy is due to NHS, which allows some oocytes to pass meiotic checkpoints without one crossing-over per chromosomal pair, leading to segregation errors, and thereby NHS links POF to aneuploidy.
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Affiliation(s)
- Srdjan Gasic
- Laboratory of Germ Cell Development, Division BIOCEV, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Ondrej Mihola
- Laboratory of Germ Cell Development, Division BIOCEV, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Zdenek Trachtulec
- Laboratory of Germ Cell Development, Division BIOCEV, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic.
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11
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Lorenz A, Mpaulo SJ. Gene conversion: a non-Mendelian process integral to meiotic recombination. Heredity (Edinb) 2022; 129:56-63. [PMID: 35393552 PMCID: PMC9273591 DOI: 10.1038/s41437-022-00523-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 03/01/2022] [Accepted: 03/02/2022] [Indexed: 12/30/2022] Open
Abstract
Meiosis is undoubtedly the mechanism that underpins Mendelian genetics. Meiosis is a specialised, reductional cell division which generates haploid gametes (reproductive cells) carrying a single chromosome complement from diploid progenitor cells harbouring two chromosome sets. Through this process, the hereditary material is shuffled and distributed into haploid gametes such that upon fertilisation, when two haploid gametes fuse, diploidy is restored in the zygote. During meiosis the transient physical connection of two homologous chromosomes (one originally inherited from each parent) each consisting of two sister chromatids and their subsequent segregation into four meiotic products (gametes), is what enables genetic marker assortment forming the core of Mendelian laws. The initiating events of meiotic recombination are DNA double-strand breaks (DSBs) which need to be repaired in a certain way to enable the homologous chromosomes to find each other. This is achieved by DSB ends searching for homologous repair templates and invading them. Ultimately, the repair of meiotic DSBs by homologous recombination physically connects homologous chromosomes through crossovers. These physical connections provided by crossovers enable faithful chromosome segregation. That being said, the DSB repair mechanism integral to meiotic recombination also produces genetic transmission distortions which manifest as postmeiotic segregation events and gene conversions. These processes are non-reciprocal genetic exchanges and thus non-Mendelian.
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Affiliation(s)
- Alexander Lorenz
- Institute of Medical Sciences (IMS), University of Aberdeen, Aberdeen, UK.
| | - Samantha J Mpaulo
- Institute of Medical Sciences (IMS), University of Aberdeen, Aberdeen, UK
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12
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Liu H, Gordon SG, Rog O. Heterologous synapsis in C. elegans is regulated by meiotic double-strand breaks and crossovers. Chromosoma 2021; 130:237-250. [PMID: 34608541 PMCID: PMC8671313 DOI: 10.1007/s00412-021-00763-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/21/2021] [Accepted: 09/23/2021] [Indexed: 10/20/2022]
Abstract
Alignment of the parental chromosomes during meiotic prophase is key to the formation of genetic exchanges, or crossovers, and consequently to the successful production of gametes. In almost all studied organisms, alignment involves synapsis: the assembly of a conserved inter-chromosomal interface called the synaptonemal complex (SC). While the SC usually synapses homologous sequences, it can assemble between heterologous sequences. However, little is known about the regulation of heterologous synapsis. Here, we study the dynamics of heterologous synapsis in the nematode C. elegans. We characterize two experimental scenarios: SC assembly onto a folded-back chromosome that cannot pair with its homologous partner; and synapsis of pseudo-homologs, a fusion chromosome partnering with an unfused chromosome half its size. We observed elevated levels of heterologous synapsis when the number of meiotic double-strand breaks or crossovers were reduced, indicating that the promiscuity of synapsis is regulated by break formation or repair. In addition, our data suggests the existence of both chromosome-specific and nucleus-wide regulation on heterologous synapsis.
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Affiliation(s)
- Hanwenheng Liu
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112-0840, USA
- The Division of Biology & Biomedical Sciences, Washington University in St. Louis, 660 South Euclid Avenue, Missouri, 63110, USA
| | - Spencer G Gordon
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112-0840, USA
| | - Ofer Rog
- School of Biological Sciences and Center for Cell and Genome Sciences, University of Utah, 257 South 1400 East, Salt Lake City, UT, 84112-0840, USA.
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13
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Imai Y, Olaya I, Sakai N, Burgess SM. Meiotic Chromosome Dynamics in Zebrafish. Front Cell Dev Biol 2021; 9:757445. [PMID: 34692709 PMCID: PMC8531508 DOI: 10.3389/fcell.2021.757445] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 09/14/2021] [Indexed: 11/13/2022] Open
Abstract
Recent studies in zebrafish have revealed key features of meiotic chromosome dynamics, including clustering of telomeres in the bouquet configuration, biogenesis of chromosome axis structures, and the assembly and disassembly of the synaptonemal complex that aligns homologs end-to-end. The telomere bouquet stage is especially pronounced in zebrafish meiosis and sub-telomeric regions play key roles in mediating pairing and homologous recombination. In this review, we discuss the temporal progression of these events in meiosis prophase I and highlight the roles of proteins associated with meiotic chromosome architecture in homologous recombination. Finally, we discuss the interplay between meiotic mutants and gonadal sex differentiation and future research directions to study meiosis in living cells, including cell culture.
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Affiliation(s)
- Yukiko Imai
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan
| | - Ivan Olaya
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States.,Integrative Genetics and Genomics Graduate Group, University of California, Davis, Davis, CA, United States
| | - Noriyoshi Sakai
- Department of Gene Function and Phenomics, National Institute of Genetics, Mishima, Japan.,Department of Genetics, School of Life Sciences, SOKENDAI (The Graduate University for Advanced Studies), Mishima, Japan
| | - Sean M Burgess
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
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14
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Zhang FG, Zhang RR, Gao JM. The organization, regulation, and biological functions of the synaptonemal complex. Asian J Androl 2021; 23:580-589. [PMID: 34528517 PMCID: PMC8577265 DOI: 10.4103/aja202153] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The synaptonemal complex (SC) is a meiosis-specific proteinaceous macromolecular structure that assembles between paired homologous chromosomes during meiosis in various eukaryotes. The SC has a highly conserved ultrastructure and plays critical roles in controlling multiple steps in meiotic recombination and crossover formation, ensuring accurate meiotic chromosome segregation. Recent studies in different organisms, facilitated by advances in super-resolution microscopy, have provided insights into the macromolecular structure of the SC, including the internal organization of the meiotic chromosome axis and SC central region, the regulatory pathways that control SC assembly and dynamics, and the biological functions exerted by the SC and its substructures. This review summarizes recent discoveries about how the SC is organized and regulated that help to explain the biological functions associated with this meiosis-specific structure.
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Affiliation(s)
- Feng-Guo Zhang
- Institute of Biomedical Sciences, College of Life Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province, Shandong Normal University, Jinan 250014, China
| | - Rui-Rui Zhang
- Institute of Biomedical Sciences, College of Life Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province, Shandong Normal University, Jinan 250014, China
| | - Jin-Min Gao
- Institute of Biomedical Sciences, College of Life Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province, Shandong Normal University, Jinan 250014, China
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15
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Cahoon CK, Libuda DE. Conditional immobilization for live imaging Caenorhabditis elegans using auxin-dependent protein depletion. G3-GENES GENOMES GENETICS 2021; 11:6362942. [PMID: 34534266 PMCID: PMC8527506 DOI: 10.1093/g3journal/jkab310] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 08/19/2021] [Indexed: 11/12/2022]
Abstract
The visualization of biological processes using fluorescent proteins and dyes in living organisms has enabled numerous scientific discoveries. The nematode Caenorhabditis elegans is a widely used model organism for live imaging studies since the transparent nature of the worm enables imaging of nearly all tissues within a whole, intact animal. While current techniques are optimized to enable the immobilization of hermaphrodite worms for live imaging, many of these approaches fail to successfully restrain the smaller male worms. To enable live imaging of worms of both sexes, we developed a new genetic, conditional immobilization tool that uses the auxin-inducible degron (AID) system to immobilize both adult and larval hermaphrodite and male worms for live imaging. Based on chromosome location, mutant phenotype, and predicted germline consequence, we identified and AID-tagged three candidate genes (unc-18, unc-104, and unc-52). Strains with these AID-tagged genes were placed on auxin and tested for mobility and germline defects. Among the candidate genes, auxin-mediated depletion of UNC-18 caused significant immobilization of both hermaphrodite and male worms that was also partially reversible upon removal from auxin. Notably, we found that male worms require a higher concentration of auxin for a similar amount of immobilization as hermaphrodites, thereby suggesting a potential sex-specific difference in auxin absorption and/or processing. In both males and hermaphrodites, depletion of UNC-18 did not largely alter fertility, germline progression, nor meiotic recombination. Finally, we demonstrate that this new genetic tool can successfully immobilize both sexes enabling live imaging studies of sexually dimorphic features in C. elegans.
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Affiliation(s)
- Cori K Cahoon
- Department of Biology, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403-1229, USA
| | - Diana E Libuda
- Department of Biology, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403-1229, USA
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16
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Beverley R, Snook ML, Brieño-Enríquez MA. Meiotic Cohesin and Variants Associated With Human Reproductive Aging and Disease. Front Cell Dev Biol 2021; 9:710033. [PMID: 34409039 PMCID: PMC8365356 DOI: 10.3389/fcell.2021.710033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 07/13/2021] [Indexed: 12/19/2022] Open
Abstract
Successful human reproduction relies on the well-orchestrated development of competent gametes through the process of meiosis. The loading of cohesin, a multi-protein complex, is a key event in the initiation of mammalian meiosis. Establishment of sister chromatid cohesion via cohesin rings is essential for ensuring homologous recombination-mediated DNA repair and future proper chromosome segregation. Cohesin proteins loaded during female fetal life are not replenished over time, and therefore are a potential etiology of age-related aneuploidy in oocytes resulting in decreased fecundity and increased infertility and miscarriage rates with advancing maternal age. Herein, we provide a brief overview of meiotic cohesin and summarize the human genetic studies which have identified genetic variants of cohesin proteins and the associated reproductive phenotypes including primary ovarian insufficiency, trisomy in offspring, and non-obstructive azoospermia. The association of cohesion defects with cancer predisposition and potential impact on aging are also described. Expansion of genetic testing within clinical medicine, with a focus on cohesin protein-related genes, may provide additional insight to previously unknown etiologies of disorders contributing to gamete exhaustion in females, and infertility and reproductive aging in both men and women.
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Affiliation(s)
- Rachel Beverley
- Division of Reproductive Endocrinology and Infertility, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, United States
| | - Meredith L Snook
- Division of Reproductive Endocrinology and Infertility, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, United States
| | - Miguel Angel Brieño-Enríquez
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, United States
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Abstract
The formation of crossovers between homologous chromosomes is key to sexual reproduction. In most species, crossovers are spaced further apart than would be expected if they formed independently, a phenomenon termed crossover interference. Despite more than a century of study, the molecular mechanisms implementing crossover interference remain a subject of active debate. Recent findings of how signaling proteins control the formation of crossovers and about the interchromosomal interface in which crossovers form offer new insights into this process. In this Review, we present a cell biological and biophysical perspective on crossover interference, summarizing the evidence that links interference to the spatial, dynamic, mechanical and molecular properties of meiotic chromosomes. We synthesize this physical understanding in the context of prevailing mechanistic models that aim to explain how crossover interference is implemented.
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Affiliation(s)
- Lexy von Diezmann
- Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT 84112, USA.,School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Ofer Rog
- Center for Cell and Genome Sciences, University of Utah, Salt Lake City, UT 84112, USA.,School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
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Abstract
Meiotic double-strand break repair is a highly regulated process usually occurring between homologs. Assessing repair in metazoans using the sister chromatid has previously been technically challenging. Two new studies show that, while rare, sister chromatid repair occurs in Caenorhabditis elegans.
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Affiliation(s)
| | - Stacie E Hughes
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
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Toraason E, Horacek A, Clark C, Glover ML, Adler VL, Premkumar T, Salagean A, Cole F, Libuda DE. Meiotic DNA break repair can utilize homolog-independent chromatid templates in C. elegans. Curr Biol 2021; 31:1508-1514.e5. [PMID: 33740427 DOI: 10.1016/j.cub.2021.03.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 02/09/2021] [Accepted: 03/02/2021] [Indexed: 02/06/2023]
Abstract
During meiosis, the maintenance of genome integrity is critical for generating viable haploid gametes.1 In meiotic prophase I, double-strand DNA breaks (DSBs) are induced and a subset of these DSBs are repaired as interhomolog crossovers to ensure proper chromosome segregation. DSBs not resolved as crossovers with the homolog must be repaired by other pathways to ensure genome integrity.2 To determine if alternative repair templates can be engaged for meiotic DSB repair during oogenesis, we developed an assay to detect sister and/or intra-chromatid repair events at a defined DSB site during Caenorhabditis elegans meiosis. Using this assay, we directly demonstrate that the sister chromatid or the same DNA molecule can be engaged as a meiotic repair template for both crossover and noncrossover recombination, with noncrossover events being the predominant recombination outcome. We additionally find that the sister or intra-chromatid substrate is available as a recombination partner for DSBs induced throughout meiotic prophase I, including late prophase when the homolog is unavailable. Analysis of noncrossover conversion tract sequences reveals that DSBs are processed similarly throughout prophase I. We further present data indicating that the XPF-1 nuclease functions in late prophase to promote sister or intra-chromatid repair at steps of recombination following joint molecule processing. Despite its function in sister or intra-chromatid repair, we find that xpf-1 mutants do not exhibit severe defects in progeny viability following exposure to ionizing radiation. Overall, we propose that C. elegans XPF-1 may assist as an intersister or intrachromatid resolvase only in late prophase I.
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Affiliation(s)
- Erik Toraason
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA
| | - Anna Horacek
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA
| | - Cordell Clark
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA
| | - Marissa L Glover
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA
| | - Victoria L Adler
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA
| | - Tolkappiyan Premkumar
- Department of Epigenetics and Molecular Carcinogenesis, MD Anderson Cancer Center, 1808 Park Road 1C, Smithville, TX 78957, USA
| | - Alina Salagean
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA
| | - Francesca Cole
- Department of Epigenetics and Molecular Carcinogenesis, MD Anderson Cancer Center, 1808 Park Road 1C, Smithville, TX 78957, USA
| | - Diana E Libuda
- Institute of Molecular Biology, Department of Biology, University of Oregon, 1229 Franklin Boulevard, Eugene, OR 97403, USA.
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