Transcriptome studies of granulosa cells at different stages of ovarian follicular development in buffalo.

The normal maturation and ovulation from ovarian follicles is important in ensuring conception and improving fertility of buffalo. The molecular regulation mechanism of buffalo follicles growth, however, remains unknown. This study analyzed the gene expression profiles associated with buffalo ovarian follicle growth. According to the analysis of RNA sequencing, 17,700 unigenes and 13,672 differentially expressed genes (DEGs) were detected. A total of 30 common DEGs were identified during four stages of follicle growth, and the expression patterns are basically synchronized, suggesting the products as a result of expressions of these genes may cooperate to regulate follicular development. Furthermore, GO and KEGG enrichment analyses revealed that the majority of DEGs in early stage of follicular growth were enriched in ribosomal and oxidative phosphorylation signaling pathways, and the expression patterns of these DEGs are basically up-regulated at the beginning of follicular growth (<8mm, diameter), and then down-regulated (8-12mm) in the following stages of follicular development. The pathway of immune signaling, including allograft rejection, chemokine signaling pathway, natural killer cell mediated cytotoxicity, phagosome, and antigen processing and presentation, was significantly enriched in the last stage of follicular development (>12mm), which indicates that the immune system has an important role in the last stage of follicular maturation and ovulation. This study provided a gene expression profile of buffalo follicle growth, and provided an insight into biological processes associated with molecular regulation of ovarian follicle growth.