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Global changes in granulosa cell chromatin accessibility in response to the LH surge and to PGR (ATAC-seq)

ABSTRACT: During ovulation, the LH surge leads to the activation of various signalling cascades in granulosa cells, resulting in a critical shift in chromatin landscape and correspondingly the ovarian gene expression profile. Such large-scale genomic reprogramming involves a specific suite of ovulatory transcription factors. An essential factor for ovulation is the progesterone receptor (PGR). One of the ways through which PGR can mediate transcription regulation is through interaction with histone and chromatin remodellers to facilitate chromatin reprogramming and thereby enabling transcription. However, it is unknown whether this mechanism is employed by PGR in granulosa cells. This study aims to characterise global changes in the chromatin landscape that are induced by the LH surge and to determine the role of PGR in facilitating chromatin accessibility in granulosa cells during ovulation.

ORGANISM(S): Mus musculus

PROVIDER: GSE166878 | GEO | 2022/02/15

REPOSITORIES: GEO

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Project description:The molecular mechanisms that regulate the pivotal transformation processes observed in the follicular wall following the pre-ovulatory LH-surge, are still not established, particularly for cells of the thecal layer. To elucidate thecal and granulosa cell type-specific biological functions and signaling pathways, large dominant bovine follicles were collected before and 21 hrs after an exogenous GnRH induced LH surge. Because LH receptor density varies within the granulosa cell populations, antral granulosa (aGC; those aspirated by follicular puncture) and membrane associated granulosa (mGC; those scraped from the follicular wall) were compared to thecal cell expression profiles determined by mRNA microarrays. Thecal cell gene expression was less affected in the peri-ovulatory follicle when compared to granulosa cells, as evidenced by only 2% versus 25% of the ~11,000 genes expressed changing in response to the LH surge, respectively. The majority of the 203 LH-regulated thecal genes were also LH regulated in granulosa cells, leaving a total of 58 genes as LH-regulated theca cell specific genes. Most of the 58 genes (i.e., 74%) thecal specific genes including several known thecal markers (CYP17A1, NR5A1) were downregulated, while most genes identified are new to theca. Many of the newly identified upregulated thecal genes (e.g., PTX3, RND3, PPP4R4) were also upregulated in granulosa. Minimal expression differences were observed between aGC and mGC, however, transcripts encoding extracellular proteins (NID2) and matrix modulators (ADAMTS1, SASH1) predominated these differences. We also identified large numbers of unknown LH-regulated granulosa cell genes and discuss their putative roles in ovarian function. The single dominant ovarian follicle was collected from each cow before the LH surge or 22 hours after GnRH (used to induce LH surge). RNA was extracted from three independent cells within each follicle and there were hybridized on Affymetrix microarrays.

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Global changes in granulosa cell chromatin accessibility in response to the LH surge and to PGR (ATAC-seq)

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