Profiling of RNA N6-methyladenosine methylation during follicle selection in chicken ovary.

Ovarian follicle selection is the critical step which determines the oocyte development and ovulation. In avian species, the somatic cells in the follicles decide the process of follicle selection but the precise molecular regulation is not well defined. N6-methyladenosine (m6A) is a ubiquitous reversible epigenetic RNA modification that plays an important role in the gene expression regulation and cell functions. In this study, we profiled transcriptome-wide m6A methylation in chicken follicles during follicular selection process in order to identify key factors involved in the follicle selection. The chicken follicle transcriptome was extensively methylated by m6A and a negative correlation was found between the m6A methylation enrichment and gene expression levels. Interestingly, both the m6A methylation peaks and the m6A modified transcripts increased during follicle selection, which lead to the dynamic expression of many folliculogenesis relevant genes. Functional enrichment analysis indicated that m6A modification of key factors in Wnt pathway could play a major role in regulating follicle selection. This study is the first to comprehensively characterize the m6A patterns in the chicken transcriptome, and provides deep insights into the m6A topology and relevant molecular mechanisms underlying follicle selection.