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BioRxiv : the Preprint Server For... Mar 2024When germ cells transition from the mitotic cycle into meiotic prophase I (MPI), chromosomes condense into an array of chromatin loops that are required to promote...
When germ cells transition from the mitotic cycle into meiotic prophase I (MPI), chromosomes condense into an array of chromatin loops that are required to promote homolog pairing and genetic recombination. To identify the changes in chromosomal conformation, we isolated nuclei on a trajectory from spermatogonia to the end of MPI. At each stage along this trajectory, we built genomic interaction maps with the highest temporal and spatial resolution to date. The changes in chromatin folding coincided with a concurrent decline in mitotic cohesion and a rise in meiotic cohesin complexes. We found that the stereotypical large-scale A and B compartmentalization was lost during meiotic prophase I alongside the loss of topological associating domains (TADs). Still, local subcompartments were detected and maintained throughout meiosis. The enhanced Micro-C resolution revealed that, despite the loss of TADs, higher frequency contact sites between two loci were detectable during meiotic prophase I coinciding with CTCF bound sites. The pattern of interactions around these CTCF sites with their neighboring loci showed that CTCF sites were often anchoring the meiotic loops. Additionally, the localization of CTCF to the meiotic axes indicated that these anchors were at the base of loops. Strikingly, even in the face of the dramatic reconfiguration of interphase chromatin into a condensed loop-array, the interactions between regulatory elements remained well preserved. This establishes a potential mechanism for how the meiotic chromatin maintains active transcription within a highly structured genome. In summary, the high temporal and spatial resolution of these data revealed previously unappreciated aspects of mammalian meiotic chromatin organization.
PubMed: 38903112
DOI: 10.1101/2024.03.25.586627 -
Experimental Cell Research Jun 2024Mouse HORMAD1 is a phospho-protein involved in multiple functions during meiotic prophase I. To obtain insight into the significance of its phosphorylation, we generated...
Mouse HORMAD1 is a phospho-protein involved in multiple functions during meiotic prophase I. To obtain insight into the significance of its phosphorylation, we generated phospho-specific antibodies against two serine residues, Ser307 and Ser378, representing each of two serine clusters in mouse HORMAD1. The Ser307 phosphorylation is detectable from early leptotene substage in both wild-type and Spo11 spermatocytes, indicating that Ser307 is a primary and SPO11-independent phosphorylation site. In contrast, the Ser378 phosphorylation is negligible at earlier substages in wild-type and Spo11 spermatocytes. After mid-zygotene substage, the Ser378 phosphorylation is abundant on unsynapsed chromosome axes in wild-type spermatocytes and is detected only in a part of unsynapsed chromosome axes in Spo11 spermatocytes. We also generated a non-phosphorylated Ser307-specific antibody and found that Ser307 is phosphorylated on sex chromosome axes but is almost entirely unphosphorylated on desynapsed chromosome axes in diplotene spermatocytes. These results demonstrated a substage-specific phosphorylation status of mouse HORMAD1, which might be associated with multiple substage-specific functions.
PubMed: 38897409
DOI: 10.1016/j.yexcr.2024.114133 -
BioRxiv : the Preprint Server For... Jun 2024The oocyte germline of the hermaphrodite presents a unique model to study the formation of oocytes. However, the size of the model animal and difficulties in retrieval...
The oocyte germline of the hermaphrodite presents a unique model to study the formation of oocytes. However, the size of the model animal and difficulties in retrieval of specific stages of the germline have obviated closer systematic studies of this process throughout the years. Here, we present a transcriptomic level analysis into the oogenesis of hermaphrodites. We dissected a hermaphrodite gonad into seven sections corresponding to the mitotic distal region, the pachytene, the diplotene, the early diakinesis region and the 3 most proximal oocytes, and deeply sequenced the transcriptome of each of them along with that of the fertilized egg using a single-cell RNA-seq protocol. We identified specific gene expression events as well as gene splicing events in finer detail along the oocyte germline and provided novel insights into underlying mechanisms of the oogenesis process. Furthermore, through careful review of relevant research literature coupled with patterns observed in our analysis, we attempt to delineate transcripts that may serve functions in the interaction between the germline and cells of the somatic gonad. These results expand our knowledge of the transcriptomic space of the germline and lay a foundation on which future studies of the germline can be based upon.
PubMed: 38895354
DOI: 10.1101/2024.06.03.597235 -
Biological Research May 2024Helicase for meiosis 1 (HFM1), a putative DNA helicase expressed in germ-line cells, has been reported to be closely associated with premature ovarian insufficiency...
BACKGROUND
Helicase for meiosis 1 (HFM1), a putative DNA helicase expressed in germ-line cells, has been reported to be closely associated with premature ovarian insufficiency (POI). However, the underlying molecular mechanism has not been clearly elucidated. The aim of this study was to investigate the function of HFM1 in the first meiotic prophase of mouse oocytes.
RESULTS
The results suggested that the deficiency of HFM1 resulting in increased apoptosis and depletion of oocytes in mice, while the oocytes were arrested in the pachytene stage of the first meiotic prophase. In addition, impaired DNA double-strand break repair and disrupted synapsis were observed in the absence of HFM1. Further investigation revealed that knockout of HFM1 promoted ubiquitination and degradation of FUS protein mediated by FBXW11. Additionally, the depletion of HFM1 altered the intranuclear localization of FUS and regulated meiotic- and oocyte development-related genes in oocytes by modulating the expression of BRCA1.
CONCLUSIONS
These findings elaborated that the critical role of HFM1 in orchestrating the regulation of DNA double-strand break repair and synapsis to ensure meiosis procession and primordial follicle formation. This study provided insights into the pathogenesis of POI and highlighted the importance of HFM1 in maintaining proper meiotic function in mouse oocytes.
Topics: Animals; Female; Mice; Apoptosis; DNA Breaks, Double-Stranded; DNA Repair; Meiosis; Meiotic Prophase I; Mice, Knockout; Oocytes; RNA-Binding Protein FUS; Ubiquitination
PubMed: 38822414
DOI: 10.1186/s40659-024-00518-w -
Horticulture Research May 2024Less-seed and seedless traits are desirable characteristics in watermelon (). Hybridization between watermelon chromosomal translocated lines and wild lines...
Less-seed and seedless traits are desirable characteristics in watermelon (). Hybridization between watermelon chromosomal translocated lines and wild lines significantly reduced seed counts in the hybrid fruits, approaching even seedless. However, the allelic relationships and the chromosomal translocation breakpoints from different sources are unclear, which limits their utility in breeding practices. This study focused on three groups of chromosomal translocation materials from different sources and conducted inheritance and allelic relationship analysis of translocation points. The results from third-generation genome sequencing and fluorescence in situ hybridization (FISH) revealed that the specific translocations in the naturally mutated material MT-a involved reciprocal translocations between Chr6 and Chr10. The Coγ radiation-induced mutant material MT-b involved reciprocal translocations between Chr1 and Chr5, Chr4 and Chr8. The Coγ radiation-induced mutant material MT-c involved complex translocations among Chr1, Chr5, and Chr11. Cytological observation showed that heterozygous translocation hybrids showed chromosomal synapsis abnormalities during meiotic diakinesis. Further, dominant and codominant molecular markers were developed on both sides of the translocation breakpoints, which could facilitate rapid and efficient identification of chromosome translocation lines. This study provides technical guidance for utilizing chromosomal translocation materials in the development of less-seed watermelon varieties.
PubMed: 38799123
DOI: 10.1093/hr/uhae087 -
Molecular Aspects of Medicine Jun 2024Meiosis is a critical step for spermatogenesis and oogenesis. Meiosis commences with pre-meiotic S phase that is subsequently followed by meiotic prophase. The meiotic... (Review)
Review
Meiosis is a critical step for spermatogenesis and oogenesis. Meiosis commences with pre-meiotic S phase that is subsequently followed by meiotic prophase. The meiotic prophase is characterized by the meiosis-specific chromosomal events such as chromosome recombination and homolog synapsis. Meiosis initiator (MEIOSIN) and stimulated by retinoic acid gene 8 (STRA8) initiate meiosis by activating the meiotic genes by installing the meiotic prophase program at pre-meiotic S phase. This review highlights the mechanisms of meiotic initiation and meiotic prophase progression from the point of the gene expression program and its relevance to infertility. Furthermore, upstream pathways that regulate meiotic initiation will be discussed in the context of spermatogenic development, indicating the sexual differences in the mode of meiotic entry.
Topics: Spermatogenesis; Humans; Meiosis; Animals; Male; Meiotic Prophase I; Prophase
PubMed: 38797021
DOI: 10.1016/j.mam.2024.101282 -
PLoS Computational Biology May 2024During meiosis, pairing of homologous chromosomes (homologs) ensures the formation of haploid gametes from diploid precursor cells, a prerequisite for sexual...
During meiosis, pairing of homologous chromosomes (homologs) ensures the formation of haploid gametes from diploid precursor cells, a prerequisite for sexual reproduction. Pairing during meiotic prophase I facilitates crossover recombination and homolog segregation during the ensuing reductional cell division. Mechanisms that ensure stable homolog alignment in the presence of an excess of non-homologous chromosomes have remained elusive, but rapid chromosome movements appear to play a role in the process. Apart from homolog attraction, provided by early intermediates of homologous recombination, dissociation of non-homologous associations also appears to contribute to homolog pairing, as suggested by the detection of stable non-homologous chromosome associations in pairing-defective mutants. Here, we have developed an agent-based model for homolog pairing derived from the dynamics of a naturally occurring chromosome ensemble. The model simulates unidirectional chromosome movements, as well as collision dynamics determined by attractive and repulsive forces arising from close-range physical interactions. Chromosome number and size as well as movement velocity and repulsive forces are identified as key factors in the kinetics and efficiency of homologous pairing in addition to homolog attraction. Dissociation of interactions between non-homologous chromosomes may contribute to pairing by crowding homologs into a limited nuclear area thus creating preconditions for close-range homolog attraction. Incorporating natural chromosome lengths, the model accurately recapitulates efficiency and kinetics of homolog pairing observed for wild-type and mutant meiosis in budding yeast, and can be adapted to nuclear dimensions and chromosome sets of other organisms.
Topics: Meiosis; Chromosome Pairing; Models, Genetic; Saccharomyces cerevisiae; Chromosomes, Fungal; Cell Nucleus; Computer Simulation; Computational Biology
PubMed: 38739641
DOI: 10.1371/journal.pcbi.1011416 -
Nature Communications Apr 2024Meiotic prophase progression is differently regulated in males and females. In males, pachytene transition during meiotic prophase is accompanied by robust alteration in...
Meiotic prophase progression is differently regulated in males and females. In males, pachytene transition during meiotic prophase is accompanied by robust alteration in gene expression. However, how gene expression is regulated differently to ensure meiotic prophase completion in males remains elusive. Herein, we identify HSF5 as a male germ cell-specific heat shock transcription factor (HSF) for meiotic prophase progression. Genetic analyzes and single-cell RNA-sequencing demonstrate that HSF5 is essential for progression beyond the pachytene stage under non-stress conditions rather than heat stress. Chromatin binding analysis in vivo and DNA-binding assays in vitro suggest that HSF5 binds to promoters in a subset of genes associated with chromatin organization. HSF5 recognizes a DNA motif different from typical heat shock elements recognized by other canonical HSFs. This study suggests that HSF5 is an atypical HSF that is required for the gene expression program for pachytene transition during meiotic prophase in males.
Topics: Mice; Male; Heat Shock Transcription Factors; Meiotic Prophase I; Mice, Knockout; Mice, Inbred C57BL; Spermatogenesis; Testis; Heat-Shock Response; Female
PubMed: 38684656
DOI: 10.1038/s41467-024-47601-0 -
Scientific Reports Apr 2024DNA double-strand breaks (DSBs) activate DNA damage responses (DDRs) in both mitotic and meiotic cells. A single-stranded DNA (ssDNA) binding protein, Replication...
DNA double-strand breaks (DSBs) activate DNA damage responses (DDRs) in both mitotic and meiotic cells. A single-stranded DNA (ssDNA) binding protein, Replication protein-A (RPA) binds to the ssDNA formed at DSBs to activate ATR/Mec1 kinase for the response. Meiotic DSBs induce homologous recombination monitored by a meiotic DDR called the recombination checkpoint that blocks the pachytene exit in meiotic prophase I. In this study, we further characterized the essential role of RPA in the maintenance of the recombination checkpoint during Saccharomyces cerevisiae meiosis. The depletion of an RPA subunit, Rfa1, in a recombination-defective dmc1 mutant, fully alleviates the pachytene arrest with the persistent unrepaired DSBs. RPA depletion decreases the activity of a meiosis-specific CHK2 homolog, Mek1 kinase, which in turn activates the Ndt80 transcriptional regulator for pachytene exit. These support the idea that RPA is a sensor of ssDNAs for the activation of meiotic DDR. Rfa1 depletion also accelerates the prophase I delay in the zip1 mutant defective in both chromosome synapsis and the recombination, consistent with the notion that the accumulation of ssDNAs rather than defective synapsis triggers prophase I delay in the zip1 mutant.
Topics: Replication Protein A; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Meiosis; DNA Breaks, Double-Stranded; Cell Cycle Proteins; DNA-Binding Proteins; Recombination, Genetic; Homologous Recombination; MAP Kinase Kinase 1; DNA, Single-Stranded; Nuclear Proteins; Transcription Factors
PubMed: 38664461
DOI: 10.1038/s41598-024-60082-x -
Nucleic Acids Research May 2024Accurate chromosome segregation during meiosis requires the establishment of at least one crossover (CO) between each pair of homologous chromosomes. CO formation...
Accurate chromosome segregation during meiosis requires the establishment of at least one crossover (CO) between each pair of homologous chromosomes. CO formation depends on a group of conserved pro-CO proteins, which colocalize at CO-designated sites during late meiotic prophase I. However, it remains unclear whether these pro-CO proteins form a functional complex and how they promote meiotic CO formation in vivo. Here, we show that COSA-1, a key component required for CO formation, interacts with other pro-CO factors, MSH-5 and ZHP-3, via its N-terminal disordered region. Point mutations that impair these interactions do not affect CO designation, but they strongly hinder the accumulation of COSA-1 at CO-designated sites and result in defective CO formation. These defects can be partially bypassed by artificially tethering an interaction-compromised COSA-1 derivate to ZHP-3. Furthermore, we revealed that the accumulation of COSA-1 into distinct foci is required to assemble functional 'recombination nodules'. These prevent early CO-designated recombination intermediates from being dismantled by the RTEL-1 helicase and protect late recombination intermediates, such as Holliday junctions, until they are resolved by CO-specific resolvases. Altogether, our findings provide insight into COSA-1 mediated pro-CO complex assembly and its contribution to CO formation.
Topics: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins; Chromosome Segregation; Crossing Over, Genetic; DNA-Binding Proteins; Meiosis
PubMed: 38412290
DOI: 10.1093/nar/gkae130