Project description:Chromosomes pair and synapse with their homologous partners to segregate correctly at meiosis I. Association of telomeres with the LINC (Linker of Nucleoskeleton and Cytoskeleton) complex enables telomere-led chromosome movements and telomere bouquet formation, facilitating precise pairwise alignment of homologs. Here, we identify a direct interaction between SUN1 and Speedy A (SPDYA) and determine the crystal structure of human SUN1-SPDYA-CDK2 ternary complex. Analysis of meiosis prophase I process in SPDYA-binding-deficient SUN1 mutant mice reveals that the SUN1-SPDYA interaction is required for the telomere-LINC complex connection and the assembly of a ring-shaped telomere supramolecular architecture at the nuclear envelope, which is critical for efficient homologous pairing and synapsis. Overall, our results provide structural insights into meiotic telomere structure that is essential for meiotic prophase progression.
Project description:Here we used phosphoproteomics to define meiosis-specific ATR signaling events during prophase I in mice following chemical and genetic ablation of ATR signaling. Quantitative analysis of phosphoproteomes obtained after tissue-specific genetic ablation of the ATR activating 9-1-1 complex or treatment with ATR inhibitor revealed over 49,800 phosphorylation sites from testes samples, of which 401 phosphorylation sites were found to be dependent on both the 9-1-1 complex and ATR kinase.
Project description:The meiosis-specific chromosomal events of homolog pairing, synapsis, and recombination occur over an extended meiotic prophase I. In this study, we show that, in mice, maintenance of an extended meiotic prophase I requires the gene Meioc, a germ-cell specific factor conserved in most metazoans. Using immunoprecipitation and quantitative mass spectrometry, we identify proteins that interact with MEIOC in the mouse germ line.
Project description:Male germ cell meiosis is essential for generating haploid spermatozoa in mice. Here, we investigate the essential role of DIS3 in male germ cell meiosis in mice. Conditional inactivation of DIS3 in spermatocytes with Stra8-cre transgenic mice have severely impaired meiotic progression, which results in defective meiosis and spermatogenesis. RNA-seq analysis reveals that Dis3 deficiency causes significant dysregulation of the expression of transcripts in mutant testes. Meiosis-associated genes are significantly decreased in the absence of DIS3. Therefore, we show that DIS3 ribonuclease plays a critical role in germ cell meiosis during spermatogenesis in mice.
Project description:During spermatogenesis, mammalian spermatogonia undergo mitotic division, to maintain stem cell pool via self-renewal and generate differentiating progenitor cells for entry into meiotic prophase. During the perinatal stage, de novo DNA methylation occurring in pro-spermatogonia plays a key role to complete meiotic prophase and initiate meiotic division. In contrast, the role of the maintenance DNA methylation pathway for regulation of meiotic prophase, or meiotic division, in the adult is not well understood. Here, by using conditional mutants for Np95 (nuclear protein 95 kDa, also known as Uhrf1) or Dnmt1 [DNA (cytosine-5)-methyltransferase 1], two proteins that are essential for maintenance DNA methylation, we reveal that both NP95 and DNMT1 are co-expressed in spermatogonia and that these factors are necessary for meiosis in male germ cells. We found that Np95- or Dnmt1-deficient spermatocytes exhibited spermatogenic defects involving synaptic failure during meiotic prophase. In addition, assembly of pericentric heterochromatin clusters in early meiotic prophase, a phenomenon that is required for subsequent pairing of homologous chromosomes, is disrupted in Np95-deficient as well as Dnmt1-deficient spermatocytes. Based on these observations, we propose that DNA methylation established in pre-meiotic spermatogonia regulates synapsis of homologous chromosomes, and in turn quality control of male germ cells. Maintenance DNA methylation, therefore, plays a role to ensure faithful transmission of both genetic and epigenetic information to offspring.
Project description:During spermatogenesis, mammalian spermatogonia undergo mitotic division, to maintain stem cell pool via self-renewal and generate differentiating progenitor cells for entry into meiotic prophase. During the perinatal stage, de novo DNA methylation occurring in pro-spermatogonia plays a key role to complete meiotic prophase and initiate meiotic division. In contrast, the role of the maintenance DNA methylation pathway for regulation of meiotic prophase, or meiotic division, in the adult is not well understood. Here, by using conditional mutants for Np95 (nuclear protein 95 kDa, also known as Uhrf1) or Dnmt1 [DNA (cytosine-5)-methyltransferase 1], two proteins that are essential for maintenance DNA methylation, we reveal that both NP95 and DNMT1 are co-expressed in spermatogonia and that these factors are necessary for meiosis in male germ cells. We found that Np95- or Dnmt1-deficient spermatocytes exhibited spermatogenic defects involving synaptic failure during meiotic prophase. In addition, assembly of pericentric heterochromatin clusters in early meiotic prophase, a phenomenon that is required for subsequent pairing of homologous chromosomes, is disrupted in Np95-deficient as well as Dnmt1-deficient spermatocytes. Based on these observations, we propose that DNA methylation established in pre-meiotic spermatogonia regulates synapsis of homologous chromosomes, and in turn quality control of male germ cells. Maintenance DNA methylation, therefore, plays a role to ensure faithful transmission of both genetic and epigenetic information to offspring.
Project description:During meiosis, a single round of DNA replication is followed by two consecutive rounds of nuclear divisions called meiosis I and meiosis II. In meiosis I, homologous chromosomes segregate, while sister chromatids remain together. Determining how this unusual chromosome segregation behavior is established is central to understanding germ cell development. Here we show that preventing microtubule-kinetochore interactions during premeiotic S phase and prophase I is essential for establishing the meiosis I chromosome segregation pattern. Premature interactions of kinetochores with microtubules transform meiosis I into a mitosis-like division by disrupting two key meiosis I events: coorientation of sister kinetochores and protection of centromeric cohesin removal from chromosomes. Furthermore we find that restricting outer kinetochore assembly contributes to preventing premature engagement of microtubules with kinetochores. We propose that inhibition of microtubule-kinetochore interactions during premeiotic S phase and prophase I is central to establishing the unique meiosis I chromosome segregation pattern. The association of the cohesion factors Rec8, Pds5, and Sgo1 were measured by ChIP-chip analysis in wild-type and CUP-CLB3 strains.
Project description:During meiosis, a single round of DNA replication is followed by two consecutive rounds of nuclear divisions called meiosis I and meiosis II. In meiosis I, homologous chromosomes segregate, while sister chromatids remain together. Determining how this unusual chromosome segregation behavior is established is central to understanding germ cell development. Here we show that preventing microtubule-kinetochore interactions during premeiotic S phase and prophase I is essential for establishing the meiosis I chromosome segregation pattern. Premature interactions of kinetochores with microtubules transform meiosis I into a mitosis-like division by disrupting two key meiosis I events: coorientation of sister kinetochores and protection of centromeric cohesin removal from chromosomes. Furthermore we find that restricting outer kinetochore assembly contributes to preventing premature engagement of microtubules with kinetochores. We propose that inhibition of microtubule-kinetochore interactions during premeiotic S phase and prophase I is central to establishing the unique meiosis I chromosome segregation pattern.