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Proceedings of the National Academy of... Nov 2022In the early stages of meiosis, maternal and paternal chromosomes pair with their homologous partner and recombine to ensure exchange of genetic information and proper...
In the early stages of meiosis, maternal and paternal chromosomes pair with their homologous partner and recombine to ensure exchange of genetic information and proper segregation. These events can vary drastically between species and between males and females of the same species. In in contrast to females, males do not form synaptonemal complexes (SCs), do not recombine, and have no crossing over; yet, males are able to segregate their chromosomes properly. Here, we investigated the early steps of homolog pairing in males. We found that homolog centromeres are not paired in germline stem cells (GSCs) and become paired in the mitotic region before meiotic entry, similarly to females. Surprisingly, male germline cells express SC proteins, which localize to centromeres and promote pairing. We further found that the SUN/KASH (LINC) complex and microtubules are required for homolog pairing as in females. Chromosome movements in males, however, are much slower than in females and we demonstrate that this slow dynamic is compensated in males by having longer cell cycles. In agreement, slowing down cell cycles was sufficient to rescue pairing-defective mutants in female meiosis. Our results demonstrate that although meiosis differs significantly between males and females, sex-specific cell cycle kinetics integrate similar molecular mechanisms to achieve proper centromere pairing.
Topics: Animals; Male; Female; Chromosome Pairing; Drosophila; Synaptonemal Complex; Centromere; Meiosis; Chromosomes; Chromosome Segregation
PubMed: 36375065
DOI: 10.1073/pnas.2207660119 -
Journal of Molecular Cell Biology Dec 2021Meiosis produces the haploid gametes required by all sexually reproducing organisms, occurring in specific temperature ranges in different organisms. However, how...
Meiosis produces the haploid gametes required by all sexually reproducing organisms, occurring in specific temperature ranges in different organisms. However, how meiotic thermotolerance is regulated remains largely unknown. Using the model organism Caenorhabditis elegans, here, we identified the synaptonemal complex (SC) protein SYP-5 as a critical regulator of meiotic thermotolerance. syp-5-null mutants maintained a high percentage of viable progeny at 20°C but produced significantly fewer viable progeny at 25°C, a permissive temperature in wild-type worms. Cytological analysis of meiotic events in the mutants revealed that while SC assembly and disassembly, as well as DNA double-strand break repair kinetics, were not affected by the elevated temperature, crossover designation, and bivalent formation were significantly affected. More severe homolog segregation errors were also observed at elevated temperature. A temperature switching assay revealed that late meiotic prophase events were not temperature-sensitive and that meiotic defects during pachytene stage were responsible for the reduced viability of syp-5 mutants at the elevated temperature. Moreover, SC polycomplex formation and hexanediol sensitivity analysis suggested that SYP-5 was required for the normal properties of the SC, and charge-interacting elements in SC components were involved in regulating meiotic thermotolerance. Together, these findings provide a novel molecular mechanism for meiotic thermotolerance regulation.
Topics: Animals; Animals, Genetically Modified; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Computational Biology; Meiosis; Synaptonemal Complex; Thermotolerance
PubMed: 34081106
DOI: 10.1093/jmcb/mjab035 -
Cytogenetic and Genome Research 2016The cytological analysis of meiotic chromosomes is an exceptional tool to approach complex processes such as synapsis and recombination during the division. Chromosome... (Review)
Review
The cytological analysis of meiotic chromosomes is an exceptional tool to approach complex processes such as synapsis and recombination during the division. Chromosome studies of meiosis have been especially valuable in birds, where naturally occurring mutants or experimental knock-out animals are not available to fully investigate the basic mechanisms of major meiotic events. This review highlights the main contributions of synaptonemal complex and lampbrush chromosome research to the current knowledge of avian meiosis, with special emphasis on the organization of chromosomes during prophase I, the impact of chromosome rearrangements during meiosis, and distinctive features of the ZW pair.
Topics: Animals; Birds; Crossing Over, Genetic; Female; Genetic Markers; Meiosis; Meiotic Prophase I; Sex Chromosomes; Synaptonemal Complex
PubMed: 28030854
DOI: 10.1159/000453541 -
Proceedings of the National Academy of... Mar 2022SignificanceEssential for sexual reproduction, meiosis is a specialized cell division required for the production of haploid gametes. Critical to this process are the...
SignificanceEssential for sexual reproduction, meiosis is a specialized cell division required for the production of haploid gametes. Critical to this process are the pairing, recombination, and segregation of homologous chromosomes (homologs). While pairing and recombination are linked, it is not known how many linkages are sufficient to hold homologs in proximity. Here, we reveal that random diffusion and the placement of a small number of linkages are sufficient to establish the apparent "pairing" of homologs. We also show that colocalization between any two loci is more dynamic than anticipated. Our study provides observations of live interchromosomal dynamics during meiosis and illustrates the power of combining single-cell measurements with theoretical polymer modeling.
Topics: Chromosomes; Meiosis; Prophase
PubMed: 35302885
DOI: 10.1073/pnas.2115883119 -
PLoS Genetics Aug 2018In meiosis I, homologous chromosomes segregate away from each other-the first of two rounds of chromosome segregation that allow the formation of haploid gametes. In... (Review)
Review
In meiosis I, homologous chromosomes segregate away from each other-the first of two rounds of chromosome segregation that allow the formation of haploid gametes. In prophase I, homologous partners become joined along their length by the synaptonemal complex (SC) and crossovers form between the homologs to generate links called chiasmata. The chiasmata allow the homologs to act as a single unit, called a bivalent, as the chromosomes attach to the microtubules that will ultimately pull them away from each other at anaphase I. Recent studies, in several organisms, have shown that when the SC disassembles at the end of prophase, residual SC proteins remain at the homologous centromeres providing an additional link between the homologs. In budding yeast, this centromere pairing is correlated with improved segregation of the paired partners in anaphase. However, the causal relationship of prophase centromere pairing and subsequent disjunction in anaphase has been difficult to demonstrate as has been the relationship between SC assembly and the assembly of the centromere pairing apparatus. Here, a series of in-frame deletion mutants of the SC component Zip1 were used to address these questions. The identification of a separation-of-function allele that disrupts centromere pairing, but not SC assembly, has made it possible to demonstrate that centromere pairing and SC assembly have mechanistically distinct features and that the centromere pairing function of Zip1 drives disjunction of the paired partners in anaphase I.
Topics: Alleles; Anaphase; Centromere; Chromosome Pairing; Chromosome Segregation; Meiosis; Nuclear Proteins; Recombination, Genetic; Saccharomyces cerevisiae Proteins; Saccharomycetales; Synaptonemal Complex
PubMed: 30091974
DOI: 10.1371/journal.pgen.1007513 -
Current Topics in Developmental Biology 1998Meiotic division comprises a complex series of events, many of which are unique in the life cycle of the organism. The process utilizes both proteins that participate in... (Review)
Review
Meiotic division comprises a complex series of events, many of which are unique in the life cycle of the organism. The process utilizes both proteins that participate in normal mitotic cell cycle progression and DNA damage repair and proteins expressed only during meiosis. Until recently, few meiotic protein participants had been identified and characterized, but several recent developments have changed this situation. Proteins can be selected for study based on their cDNA sequence and similarity to known proteins with "suspicious" repair/recombination or cell cycle activity and antibodies against these proteins applied to meiotic nuclei to test for activity. With the development of gene sequence data bases from many organisms, similarity to a known protein need not be based on the same or even a closely related species. Potential interactions between two or more proteins can be identified and involvement in a common process inferred based on antibody colocalization. The gene sequence can be disrupted and the effect on meiotic progression directly examined. Previously identified structures, the synaptonemal complex (SC) and both early and late recombination nodules (RNs), provide structural and temporal landmarks that assist in inferring meiotic activity of the protein being studied. Mammalian meiosis is especially attractive for these kinds of studies since spermatocyte and oocyte nuclei are large with distinct nuclear organelles and since meiosis is highly protracted, occurring over a period of several days. In this chapter, an approach to the study of mammalian meiosis based on use of specific antibodies is outlined and methods of coupling this approach to other techniques, such as targeted gene disruption or chromosome aberrations, are described. Some of the proteins already identified as participants in meiotic prophase are reviewed and their presumed functions discussed.
Topics: Animals; DNA-Binding Proteins; Fungal Proteins; Genetic Diseases, Inborn; Immunohistochemistry; Meiosis; Mice; Prophase; Proteins; Rad51 Recombinase; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 9352187
DOI: 10.1016/s0070-2153(08)60175-1 -
Plant Physiology Sep 2019In most eukaryotes, a set of conserved proteins that are collectively termed ZMM proteins (named for molecular zipper 1 [ZIP1], ZIP2, ZIP3, and ZIP4, MutS homologue 4...
In most eukaryotes, a set of conserved proteins that are collectively termed ZMM proteins (named for molecular zipper 1 [ZIP1], ZIP2, ZIP3, and ZIP4, MutS homologue 4 [MSH4] and MSH5, meiotic recombination 3, and sporulation 16 [SPO16] in yeast []) are essential for the formation of the majority of meiotic crossovers (COs). Recent reports indicated that ZIP2 acts together with SPO16 and ZIP4 to control CO formation through recognizing and stabilizing early recombination intermediates in budding yeast. However, whether this mechanism is conserved in plants is not clear. Here, we characterized the functions of SHORTAGE OF CHIASMATA 1 (OsSHOC1; ZIP2 ortholog) and PARTING DANCERS (OsPTD; SPO16 ortholog) and their interactions with other ZMM proteins in rice (). We demonstrated that disruption of OsSHOC1 caused a reduction of CO numbers to ∼83% of wild-type CO numbers, whereas synapsis and early meiotic recombination steps were not affected. Furthermore, OsSHOC1 interacts with OsPTD, which is responsible for the same set of CO formations as OsSHOC1. In addition, OsSHOC1 and OsPTD are required for the normal loading of other ZMM proteins, and conversely, the localizations of OsSHOC1 and OsPTD were also affected by the absence of OsZIP4 and human enhancer of invasion 10 in rice (OsHEI10). OsSHOC1 interacts with OsZIP4 and OsMSH5, and OsPTD interacts with OsHEI10. Furthermore, bimolecular fluorescence complementation and yeast-three hybrid assays demonstrated that OsSHOC1, OsPTD, OsHEI10, and OsZIP4 were able to form various combinations of heterotrimers. Moreover, statistical and genetic analysis indicated that OsSHOC1 and OsPTD are epistatic to OsHEI10 and OsZIP4 in meiotic CO formation. Taken together, we propose that OsSHOC1, OsPTD, OsHEI10, and OsZIP4 form multiple protein complexes that have conserved functions in promoting class I CO formation.
Topics: Amino Acid Sequence; Chromosome Pairing; Crossing Over, Genetic; Multiprotein Complexes; Oryza; Plant Proteins; Sequence Alignment; Synaptonemal Complex
PubMed: 31266799
DOI: 10.1104/pp.19.00082 -
Biochemical Society Transactions Dec 2019Non-homologous end joining (NHEJ) is a major repair pathway for DNA double-strand breaks (DSBs), which is the most toxic DNA damage in cells. Unrepaired DSBs can cause... (Review)
Review
Non-homologous end joining (NHEJ) is a major repair pathway for DNA double-strand breaks (DSBs), which is the most toxic DNA damage in cells. Unrepaired DSBs can cause genome instability, tumorigenesis or cell death. DNA end synapsis is the first and probably the most important step of the NHEJ pathway, aiming to bring two broken DNA ends close together and provide structural stability for end processing and ligation. This process is mediated through a group of NHEJ proteins forming higher-order complexes, to recognise and bridge two DNA ends. Spatial and temporal understanding of the structural mechanism of DNA-end synapsis has been largely advanced through recent structural and single-molecule studies of NHEJ proteins. This review focuses on core NHEJ proteins that mediate DNA end synapsis through their unique structures and interaction properties, as well as how they play roles as anchor and linker proteins during the process of 'bridge over troubled ends'.
Topics: Chromosome Pairing; DNA; DNA Breaks, Double-Stranded; DNA End-Joining Repair; DNA-Binding Proteins; Humans; Nucleic Acid Conformation
PubMed: 31829407
DOI: 10.1042/BST20180518 -
Cell Reports May 2020Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation....
Centrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation. The major effector of centrosome separation is the kinesin Eg5. However, the identity and regulation of Eg5-antagonizing forces is less well characterized. By manipulating candidate components, we find that centrosome separation is reversible and that separated centrosomes congress toward a central position underneath the flat nucleus. This positioning mechanism requires microtubule polymerization, as well as actin polymerization. We identify perinuclear actin structures that form in late G2/early prophase and interact with microtubules emanating from the centrosomes. Disrupting these structures by breaking the interactions of the linker of nucleoskeleton and cytoskeleton (LINC) complex with perinuclear actin filaments abrogates this centrosome positioning mechanism and causes an increase in subsequent chromosome segregation errors. Our results demonstrate how geometrical cues from the cell nucleus coordinate the orientation of the emanating spindle poles before nuclear envelope breakdown.
Topics: Actins; Centrosome; Chromosome Segregation; Humans; Prophase
PubMed: 32460023
DOI: 10.1016/j.celrep.2020.107681 -
DNA Repair Oct 2023DNA double strand breaks (DSBs) are common lesions whose misrepair are drivers of oncogenic transformations. The non-homologous end joining (NHEJ) pathway repairs the... (Review)
Review
DNA double strand breaks (DSBs) are common lesions whose misrepair are drivers of oncogenic transformations. The non-homologous end joining (NHEJ) pathway repairs the majority of these breaks in vertebrates by directly ligating DNA ends back together. Upon formation of a DSB, a multiprotein complex is assembled on DNA ends which tethers them together within a synaptic complex. Synapsis is a critical step of the NHEJ pathway as loss of synapsis can result in mispairing of DNA ends and chromosome translocations. As DNA ends are commonly incompatible for ligation, the NHEJ machinery must also process ends to enable rejoining. This review describes how recent progress in single-molecule approaches and cryo-EM have advanced our molecular understanding of DNA end synapsis during NHEJ and how synapsis is coordinated with end processing to determine the fidelity of repair.
Topics: Animals; DNA End-Joining Repair; DNA; DNA-Binding Proteins; DNA Breaks, Double-Stranded; Chromosome Pairing; DNA Repair
PubMed: 37572577
DOI: 10.1016/j.dnarep.2023.103553