Transcriptomic Analysis of Bovine Oocytes at GV and MII Stages and Dynamic Changes in Key Gene Expression Patterns

The maturation of oocytes is a critical step in mammalian reproduction, involving dynamic regulation of gene expression. Therefore, investigating how gene expression varies during different stages of oocyte maturation is highly important. This study employed single-cell RNA sequencing (scRNA-seq) to analyze bovine oocytes at the germinal vesicle (GV) and metaphase II (MII) stages. The results identified 1787 differentially expressed genes (DEGs) between the two stages, with 1556 genes upregulated and 231 downregulated in the GV stage. Further investigation using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses indicated that the upregulated genes are mainly involved in mitochondrial functions and energy metabolism, whereas the downregulated genes are primarily associated with signaling pathways. Validation through RT-qPCR confirmed that COA4, TKT and GPX4 were significantly higher in GV-stage oocytes, while ISG15, MAP1LC3C and ZEB2 were notably downregulated. This study highlights significant gene expression differences between GV and MII bovine oocytes, underscoring the vital roles of genes related to energy metabolism and signaling during oocyte maturation. The expression patterns of these genes provide important molecular markers for further elucidating the mechanisms underlying oocyte maturation.