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Meiotic gene transcription programs are mediated by A-MYB and BRDT-dependent RNA Pol II pause release during mammalian prophase I [ATAC-Seq]

ABSTRACT: During meiotic prophase I, germ cells must balance transcriptional activation with meiotic recombination and chromosome synapsis, biological processes requiring extensive changes to chromatin state and structure. Here we explored the interplay between chromatin accessibility and transcription across a detailed time-course of murine male meiosis by measuring genome-wide patterns of chromatin accessibility, transcription, and processed mRNA. To understand the relationship between these parameters of gene regulation and recombination, we integrated these data with maps of double-strand break formation. Maps of nascent transcription showed that Pol II is loaded on chromatin and maintained in a paused state early during meiosis. In pachynema, paused Pol II is released in a coordinated transcriptional burst resulting in ~3-fold increase in transcription. Release from pause is mediated by the transcription factor A-MYB and the testis-specific bromodomain protein, BRDT. The burst of transcriptional activity is both temporally and spatially segregated from key steps of meiotic recombination: double strand breaks show evidence of chromatin accessibility earlier during prophase I and at distinct loci from those undergoing transcriptional activation, despite shared chromatin marks. Our findings uncover the mechanisms of transcriptional activation and how cells compartmentalize transcription and recombination during meiosis.

ORGANISM(S): Mus musculus

PROVIDER: GSE212117 | GEO | 2022/09/30

REPOSITORIES: GEO

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Project description:Dynamic nuclear architecture and chromatin organizations are the key features of the mid- prophase I in mammalian meiosis. Where the chromatin undergoes major changes, including meiosis-specific spatiotemporal arrangements and remodelling, the establishment of chromatin loop–axis structure, pairing, and crossing over between homologous chromosomes, any deficiencies in these events may induce genome instability, subsequently leading to failure to produce gametes and infertility. Despite the significance of chromatin structure, little is known about the location of chromatin marks and the necessity of their balance during meiosis prophase I. Here, we show a thorough cytological study of the surface-spread meiotic chromosomes of mouse spermatocytes for H3K9,14,18,23,27,36, H4K12,16 acetylation, and H3K4,9,27,36 methylation. Active acetylation and methylation marks on H3 and H4, such as H3K9ac, H3K14ac, H3K18ac, H3K36ac, H3K56ac, H4K12ac, H4K16ac, and H3K27me3 and H3K36me3 exhibited pan-nuclear localization away from heterochromatin. In comparison, repressive marks like H3K9me3 are localized to heterochromatin. In addition, we found that the intensities of H3K23ac, H3K27ac, and H3K9me3 enhanced during meiotic prophase I. Further, taking advantage of the delivery of small-molecule chemical inhibitors Methotrexate (MTX; heterochromatin enhancer), HMS-I1 (heterochromatin inhibitor), Anacardic acid (AA; histone acetyltransferase inhibitor), Trichostatin A (TSA; histone deacetylase inhibitor), IOX1 (JmjC demethylases inhibitor), and AZ505 (methyl transferase inhibitor) in seminiferous tubules through the rete testis route, revealed that alteration in histone modifications enhanced the centromere mislocalization, chromosome breakage, altered meiotic recombination and reduced sperm count. Notably, an imbalance in the histone modifications influences the chromosome axis length and chromatin loop size via transcriptional regulation of meiosis- specific genes. Our findings highlight the importance of balanced chromatin modifications in meiotic prophase I chromosome organization and instability.

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Meiotic gene transcription programs are mediated by A-MYB and BRDT-dependent RNA Pol II pause release during mammalian prophase I [ATAC-Seq]

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