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PLoS Genetics Nov 2023The meiotic recombination checkpoint reinforces the order of events during meiotic prophase I, ensuring the accurate distribution of chromosomes to the gametes. The AAA+...
The meiotic recombination checkpoint reinforces the order of events during meiotic prophase I, ensuring the accurate distribution of chromosomes to the gametes. The AAA+ ATPase Pch2 remodels the Hop1 axial protein enabling adequate levels of Hop1-T318 phosphorylation to support the ensuing checkpoint response. While these events are localized at chromosome axes, the checkpoint activating function of Pch2 relies on its cytoplasmic population. In contrast, forced nuclear accumulation of Pch2 leads to checkpoint inactivation. Here, we reveal the mechanism by which Pch2 travels from the cell nucleus to the cytoplasm to maintain Pch2 cellular homeostasis. Leptomycin B treatment provokes the nuclear accumulation of Pch2, indicating that its nucleocytoplasmic transport is mediated by the Crm1 exportin recognizing proteins containing Nuclear Export Signals (NESs). Consistently, leptomycin B leads to checkpoint inactivation and impaired Hop1 axial localization. Pch2 nucleocytoplasmic traffic is independent of its association with Zip1 and Orc1. We also identify a functional NES in the non-catalytic N-terminal domain of Pch2 that is required for its nucleocytoplasmic trafficking and proper checkpoint activity. In sum, we unveil another layer of control of Pch2 function during meiosis involving nuclear export via the exportin pathway that is crucial to maintain the critical balance of Pch2 distribution among different cellular compartments.
Topics: Saccharomyces cerevisiae Proteins; Meiosis; Saccharomyces cerevisiae; Active Transport, Cell Nucleus; Nuclear Proteins; DNA-Binding Proteins; Karyopherins; Homeostasis
PubMed: 37948444
DOI: 10.1371/journal.pgen.1011026 -
Frontiers in Plant Science 2023Transposable elements (TEs) and satellite DNAs, two major categories of repetitive sequences, are expected to accumulate in non-recombining genome regions, including...
Transposable elements (TEs) and satellite DNAs, two major categories of repetitive sequences, are expected to accumulate in non-recombining genome regions, including sex-linked regions, and contribute to sex chromosome evolution. The dioecious plant, , can be used for studying the evolution of the XX/XYY sex chromosomes. In this study, we thoroughly examined the repetitive components of male and female using next-generation sequencing data followed by bioinformatics analysis and florescence hybridization (FISH). The genome has a high overall repetitive sequence composition, 68.30% in the female and 66.78% in the male genome, with abundant long terminal repeat (LTR) retrotransposons (RTs), including more Ty3/ than Ty1/ elements, particularly two Ty3/ lineages, Tekay and Retand. Most LTR-RT lineages were found dispersed across the chromosomes, though CRM and Athila elements were predominately found within the centromeres and the pericentromeric regions. The Athila elements also showed clearly higher FISH signal intensities in the Y and Y chromosomes than in the X or autosomes. Three novel satellite DNAs were specifically distributed in the centromeric and/or telomeric regions, with markedly different distributions on the X, Y, and Y chromosomes. Combined with FISH using satellite DNAs to stain chromosomes during meiotic diakinesis, we determined the synapsis pattern and distinguish pseudoautosomal regions (PARs). The results indicate that the XYY sex chromosomes of might have originated from a centric fission event. This study improves our understanding of the repetitive sequence organization of genome and provides a basis for further analysis of their chromosome evolution process.
PubMed: 37908838
DOI: 10.3389/fpls.2023.1230250 -
Biomedicines Sep 2023Diabetes mellitus is a metabolic disease that can cause systemic problems, including testicular dysfunction. Several diabetes medications have demonstrated potential...
Diabetes mellitus is a metabolic disease that can cause systemic problems, including testicular dysfunction. Several diabetes medications have demonstrated potential adverse effects on the male reproductive system; however, the effects of saxagliptin and dapagliflozin have not been sufficiently examined. This investigation studied the impacts of saxagliptin and dapagliflozin treatments on the gonads in a male mouse model of diabetes. Testicular disturbances were assessed by sperm DNA damage, diakinesis-metaphase I chromosome examination, and spermiogram analysis. Our results showed more sperm DNA damage, more spermatocyte chromosome aberrations, lower sperm motility/count, and more sperm morphological anomalies in diabetic mice than in the control mice. Dapagliflozin significantly restored all examined measures to the control values in diabetic mice, unlike saxagliptin, which exacerbated the reduction in sperm count and motility. Both drugs significantly restored the gonadal redox imbalances in diabetic mice by decreasing reactive oxygen species accumulation and increasing glutathione levels. In conclusion, our study presents preliminary evidence for the safety and efficacy of dapagliflozin in alleviating testicular abnormalities induced by diabetes, making it a promising candidate drug for patients with diabetes in their reproductive age. As saxagliptin may have negative effects on fertility, its prescription should be avoided in young male diabetic patients.
PubMed: 37893048
DOI: 10.3390/biomedicines11102674 -
Nature Communications Oct 2023The formation of RAD51/DMC1 filaments on single-stranded (ss)DNAs essential for homology search and strand exchange in DNA double-strand break (DSB) repair is tightly...
The formation of RAD51/DMC1 filaments on single-stranded (ss)DNAs essential for homology search and strand exchange in DNA double-strand break (DSB) repair is tightly regulated. FIGNL1 AAA+++ ATPase controls RAD51-mediated recombination in human cells. However, its role in gametogenesis remains unsolved. Here, we characterized a germ line-specific conditional knockout (cKO) mouse of FIGNL1. Fignl1 cKO male mice showed defective chromosome synapsis and impaired meiotic DSB repair with the accumulation of RAD51/DMC1 on meiotic chromosomes, supporting a positive role of FIGNL1 in homologous recombination at a post-assembly stage of RAD51/DMC1 filaments. Fignl1 cKO spermatocytes also accumulate RAD51/DMC1 on chromosomes in pre-meiotic S-phase. These RAD51/DMC1 assemblies are independent of meiotic DSB formation. We also showed that purified FIGNL1 dismantles RAD51 filament on double-stranded (ds)DNA as well as ssDNA. These results suggest an additional role of FIGNL1 in limiting the non-productive assembly of RAD51/DMC1 on native dsDNAs during pre-meiotic S-phase and meiotic prophase I.
Topics: Male; Humans; Animals; Mice; Meiosis; Rad51 Recombinase; DNA-Binding Proteins; ATPases Associated with Diverse Cellular Activities; DNA Breaks, Double-Stranded; Cell Cycle Proteins; Homologous Recombination; DNA; DNA Replication; Microtubule-Associated Proteins; Nuclear Proteins
PubMed: 37891173
DOI: 10.1038/s41467-023-42576-w -
BioRxiv : the Preprint Server For... Oct 2023During meiotic prophase I, recombination between homologous parental chromosomes is initiated by the formation of hundreds of programmed double-strand breaks (DSBs),...
During meiotic prophase I, recombination between homologous parental chromosomes is initiated by the formation of hundreds of programmed double-strand breaks (DSBs), each of which must be repaired with absolute fidelity to ensure genome stability of the germline. One outcome of these DSB events is the formation of Crossovers (COs), the sites of physical DNA exchange between homologs that are critical to ensure the correct segregation of parental chromosomes. However, COs account for only a small (~10%) proportion of all DSB repair events; the remaining 90% are repaired as non-crossovers (NCOs), most by synthesis dependent strand annealing. Virtually all COs are formed by coordinated efforts of the MSH4/MSH5 and MLH1/MLH3 heterodimers. The number and positioning of COs is exquisitely controlled via mechanisms that remain poorly understood, but which undoubtedly require the coordinated action of multiple repair pathways downstream of the initiating DSB. In a previous report we found evidence suggesting that the DNA helicase and Fanconi Anemia repair protein, FANCJ (BRIP1/BACH1), functions to regulate meiotic recombination in mouse. A gene-trap disruption of showed an elevated number of MLH1 foci and COs. FANCJ is known to interact with numerous DNA repair proteins in somatic cell repair contexts, including MLH1, BLM, BRCA1, and TOPBP1, and we hypothesized that FANCJ regulates CO formation through a direct interaction with MLH1 to suppress the major CO pathway. To further elucidate the function of FANCJ in meiosis, we produced three new mutant mouse lines via CRISPR/Cas9 gene editing: a full-gene deletion, a mutant line lacking the MLH1 interaction site and the N-terminal region of the Helicase domain, and a C-terminal 6xHIS-HA dual-tagged allele of . We also generated an antibody against the C-terminus of the mouse FANCJ protein. Surprisingly, while Fanconi-like phenotypes are observed within the somatic cell lineages of the full deletion line, none of the mutants show any change in either MLH1 focus counts during pachynema or total CO number at diakinesis of prophase I of meiosis. We find evidence that FANCJ and MLH1 do not interact in meiosis; further, FANCJ does not co-localize with MSH4, MLH1, or MLH3 during late prophase I. Instead, FANCJ forms discrete foci along the chromosome cores beginning in early meiotic prophase I, occasionally co-localizing with MSH4, and then becomes densely localized on unsynapsed chromosome axes in late zygonema and to the XY chromosomes in early pachynema. Strikingly, this localization strongly overlaps with BRCA1 and TOPBP1. mutants also exhibit a subtle persistence of DSBs in pachynema. Collectively, these data suggest a role for FANCJ in early DSB repair events, and possibly in the formation of NCOs, but they rule out a role for FANCJ in MLH1-mediated CO events. Thus, the role of FANCJ in meiotic cells involves different pathways and different interactors to those described in somatic cell lineages.
PubMed: 37873301
DOI: 10.1101/2023.10.06.561296 -
BioRxiv : the Preprint Server For... Oct 2023H3K9 tri-methylation (H3K9me3) plays emerging roles in gene regulation, beyond its accumulation on pericentric constitutive heterochromatin. It remains a mystery why and...
H3K9 tri-methylation (H3K9me3) plays emerging roles in gene regulation, beyond its accumulation on pericentric constitutive heterochromatin. It remains a mystery why and how H3K9me3 undergoes dynamic regulation in male meiosis. Here, we identify a novel, critical regulator of H3K9 methylation and spermatogenic heterochromatin organization: the germline-specific protein ATF7IP2 (MCAF2). We show that, in male meiosis, ATF7IP2 amasses on autosomal and X pericentric heterochromatin, spreads through the entirety of the sex chromosomes, and accumulates on thousands of autosomal promoters and retrotransposon loci. On the sex chromosomes, which undergo meiotic sex chromosome inactivation (MSCI), the DNA damage response pathway recruits ATF7IP2 to X pericentric heterochromatin, where it facilitates the recruitment of SETDB1, a histone methyltransferase that catalyzes H3K9me3. In the absence of ATF7IP2, male germ cells are arrested in meiotic prophase I. Analyses of ATF7IP2-deficient meiosis reveal the protein's essential roles in the maintenance of MSCI, suppression of retrotransposons, and global upregulation of autosomal genes. We propose that ATF7IP2 is a downstream effector of the DDR pathway in meiosis that coordinates the organization of heterochromatin and gene regulation through the spatial regulation of SETDB1-mediated H3K9me3 deposition.
PubMed: 37873266
DOI: 10.1101/2023.09.30.560314 -
Asian Journal of Andrology Oct 2023Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins. The mitochondrial...
Meiosis is the process of producing haploid gametes through a series of complex chromosomal events and the coordinated action of various proteins. The mitochondrial protease complex (ClpXP), which consists of caseinolytic mitochondrial matrix peptidase X (ClpX) and caseinolytic protease P (ClpP) and mediates the degradation of misfolded, damaged, and oxidized proteins, is essential for maintaining mitochondrial homeostasis. ClpXP has been implicated in meiosis regulation, but its precise role is currently unknown. In this study, we engineered an inducible male germ cell-specific knockout caseinolytic mitochondrial matrix peptidase X (ClpxcKO) mouse model to investigate the function of ClpX in meiosis. We found that disrupting Clpx in male mice induced germ cell apoptosis and led to an absence of sperm in the epididymis. Specifically, it caused asynapsis of homologous chromosomes and impaired meiotic recombination, resulting in meiotic arrest in the zygotene-to-pachytene transition phase. The loss of ClpX compromised the double-strand break (DSB) repair machinery by markedly reducing the recruitment of DNA repair protein RAD51 homolog 1 (RAD51) to DSB sites. This dysfunction may be due to an insufficient supply of energy from the aberrant mitochondria in ClpxcKO spermatocytes, as discerned by electron microscopy. Furthermore, ubiquitination signals on chromosomes and the expression of oxidative phosphorylation subunits were both significantly attenuated in ClpxcKO spermatocytes. Taken together, we propose that ClpX is essential for maintaining mitochondrial protein homeostasis and ensuring homologous chromosome pairing, synapsis, and recombination in spermatocytes during meiotic prophase I.
PubMed: 37856231
DOI: 10.4103/aja202343 -
BioRxiv : the Preprint Server For... Dec 2023Meiotic progression requires coordinated assembly and disassembly of protein complexes involved in chromosome synapsis and meiotic recombination. The AAA+ ATPase TRIP13...
Meiotic progression requires coordinated assembly and disassembly of protein complexes involved in chromosome synapsis and meiotic recombination. The AAA+ ATPase TRIP13 and its orthologue Pch2 are instrumental in remodeling HORMA domain proteins. Meiosis-specific HORMAD proteins are associated with unsynapsed chromosome axes but depleted from the synaptonemal complex (SC) of synapsed chromosome homologues. Here we report that TRIP13 localizes to the synapsed SC in early pachytene spermatocytes and to telomeres throughout meiotic prophase I. Loss of TRIP13 leads to meiotic arrest and thus sterility in both sexes. -null meiocytes exhibit abnormal persistence of HORMAD1 and HOMRAD2 on synapsed SC and chromosome asynapsis that preferentially affects XY and centromeric ends. These findings confirm the previously reported phenotypes of the hypomorph alleles. heterozygous () mice also exhibit meiotic defects that are less severe than the -null mice, showing that TRIP13 is a dosage-sensitive regulator of meiosis. Localization of TRIP13 to the synapsed SC is independent of SC axial element proteins such as REC8 and SYCP2/SYCP3. The N- or C-terminal FLAG-tagged TRIP13 proteins are functional and recapitulate the localization of native TRIP13 to SC and telomeres in knockin mice. Therefore, the evolutionarily conserved localization of TRIP13/Pch2 to the synapsed chromosomes provides an explanation for dissociation of HORMA domain proteins upon chromosome synapsis in diverse organisms.
PubMed: 37808842
DOI: 10.1101/2023.09.25.559355 -
ELife Oct 2023In sexually reproducing organisms, germ cells faithfully transmit the genome to the next generation by forming haploid gametes, such as eggs and sperm. Although most...
In sexually reproducing organisms, germ cells faithfully transmit the genome to the next generation by forming haploid gametes, such as eggs and sperm. Although most meiotic proteins are conserved between eggs and sperm, many aspects of meiosis are sexually dimorphic, including the regulation of recombination. The synaptonemal complex (SC), a large ladder-like structure that forms between homologous chromosomes, is essential for regulating meiotic chromosome organization and promoting recombination. To assess whether sex-specific differences in the SC underpin sexually dimorphic aspects of meiosis, we examined SC central region proteins (known as SYP proteins) in oogenesis and spermatogenesis and uncovered sex-specific roles for the SYPs in regulating meiotic recombination. We find that SC composition, specifically SYP-2, SYP-3, SYP-5, and SYP-6, is regulated by sex-specific mechanisms throughout meiotic prophase I. During pachytene, both oocytes and spermatocytes differentially regulate the stability of SYP-2 and SYP-3 within an assembled SC. Further, we uncover that the relative amount of SYP-2 and SYP-3 within the SC is independently regulated in both a sex-specific and a recombination-dependent manner. Specifically, we find that SYP-2 regulates the early steps of recombination in both sexes, while SYP-3 controls the timing and positioning of crossover recombination events across the genomic landscape in only oocytes. Finally, we find that SYP-2 and SYP-3 dosage can influence the composition of the other SYPs in the SC via sex-specific mechanisms during pachytene. Taken together, we demonstrate dosage-dependent regulation of individual SC components with sex-specific functions in recombination. These sexual dimorphic features of the SC provide insights into how spermatogenesis and oogenesis adapted similar chromosome structures to differentially regulate and execute recombination.
Topics: Animals; Female; Male; Caenorhabditis elegans; Synaptonemal Complex; Meiosis; Semen; Caenorhabditis elegans Proteins
PubMed: 37796106
DOI: 10.7554/eLife.84538 -
Reproductive Biology and Endocrinology... Oct 2023In human female primordial germ cells, the transition from mitosis to meiosis begins from the fetal stage. In germ cells, meiosis is arrested at the diplotene stage of... (Review)
Review
In human female primordial germ cells, the transition from mitosis to meiosis begins from the fetal stage. In germ cells, meiosis is arrested at the diplotene stage of prophase in meiosis I (MI) after synapsis and recombination of homologous chromosomes, which cannot be segregated. Within the follicle, the maintenance of oocyte meiotic arrest is primarily attributed to high cytoplasmic concentrations of cyclic adenosine monophosphate (cAMP). Depending on the specific species, oocytes can remain arrested for extended periods of time, ranging from months to even years. During estrus phase in animals or the menstrual cycle in humans, the resumption of meiosis occurs in certain oocytes due to a surge of luteinizing hormone (LH) levels. Any factor interfering with this process may lead to impaired oocyte maturation, which in turn affects female reproductive function. Nevertheless, the precise molecular mechanisms underlying this phenomenon has not been systematically summarized yet. To provide a comprehensive understanding of the recently uncovered regulatory network involved in oocyte development and maturation, the progress of the cellular and molecular mechanisms of oocyte nuclear maturation including meiosis arrest and meiosis resumption is summarized. Additionally, the advancements in understanding the molecular cytoplasmic events occurring in oocytes, such as maternal mRNA degradation, posttranslational regulation, and organelle distribution associated with the quality of oocyte maturation, are reviewed. Therefore, understanding the pathways regulating oocyte meiotic arrest and resumption will provide detailed insight into female reproductive system and provide a theoretical basis for further research and potential approaches for novel disease treatments.
Topics: Animals; Female; Humans; Oogenesis; Oocytes; Meiosis; Meiotic Prophase I; Ovarian Follicle
PubMed: 37784186
DOI: 10.1186/s12958-023-01143-0