Decoding Molecular Features of Bovine Oocyte Maturation by Integrating Epigenomic and Transcriptomic Analyses

During mammalian oocyte maturation, meiotic arrest takes place during prophase I at the germinal vesicle (GV) stage. Under a specific hormonal milieu, oocytes are reactivated to complete meiosis I and move to a stage of maturity at metaphase II during meiosis II. The regulatory mechanisms underlying this arrest remain incompletely understood. In this study, the epigenomic and transcriptomic data of bovine oocytes at GV and MII stages were integrated to identify differentially expressed genes (DEGs) and dynamics in chromatin accessibility. Firstly, through comparative transcriptomic analysis of bovine oocytes across the GV and MII stages, we observed significant enrichment of DEGs in pathways related to cell cycle regulation and oxidative phosphorylation. Moreover, motif enrichment analysis of differentially accessible regions (DARs) revealed the binding sites of the transcription factor ZBTB33. By combining assay for transposase-accessible chromatin sequencing (ATAC-seq) and RNA sequencing (RNA-seq) datasets, we identified two key meiosis-associated genes, CCNB1 and PAPOLG. Of note, transcription factor binding site analysis suggested that ZBTB33 may be serve as the regulatory factor for CCNB1 and PAPOLG. In summary, our findings highlight that ZBTB33 potentially regulates bovine oocyte meiosis by orchestrating chromatin accessibility at CCNB1 and PAPOLG. These new findings provide novel insight into the epigenetic regulation of meiotic progression in bovine oocytes.