HDAC2 regulates oocyte maturation in Tan sheep via its strong association with regulating H4K12 acetylation and EREG secretion

This study aimed to explore the potential mechanism of histone deacetylase 2 (HDAC2) in follicular development and oocyte maturation of Tan sheep, and clarify whether it affects oocyte maturation by responding to luteinizing hormone (LH) signals, regulating histone acetylation, and promoting epidermal growth factor (EGF)-like factor secretion. The effect of HDAC2 inhibitor on oocyte maturation rate was evaluated via the Cumulus-oocyte complex (COC) and granulosa cell co-culture system. Related indicators were detected using immunohistochemistry, immunofluorescence, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Western blotting, and enzyme-linked immunosorbent assay (ELISA). Results showed that HDAC2 was localized in the nuclei of granulosa cells and oocytes in all stages of Tan sheep follicles, with its expression significantly upregulated during follicular development (P < 0.001). RT-qPCR and Western blotting results confirmed that FSH significantly upregulated HDAC2 mRNA and protein expression in granulosa cells (P < 0.05 or P < 0.01), while LH significantly downregulated HDAC2 mRNA and protein levels after 2-hour treatment (P < 0.01 or P < 0.0001). Treatment with 20 μM CAY10683, a specific HDAC2 inhibitor, significantly increased the acetylation level of histone H4 lysine 12 (H4K12ac) in granulosa cells (P < 0.001), and specifically promoted the secretion and expression of epiregulin (EREG) in granulosa cells at both mRNA and protein levels (P < 0.01 or P < 0.001). Additionally, CAY10683 enhanced the in vitro maturation rate of oocytes. In conclusion, HDAC2 affects Tan sheep oocyte maturation by responding to LH signals, and the results suggest a potential link between H4K12 acetylation and EREG secretion in this process, providing a basis for studying the epigenetic regulation of sheep oocytes.