The transcriptome-wide N6-methyladenosine (mA) map profiling reveals the regulatory role of mA in the yak ovary.

BACKGROUND AND AIM

Yak estrus is a seasonal phenomenon, probably involving epigenetic regulation of synthesis and secretion of sex hormones as well as growth and development of follicles. N6-methyladenosine (mA) is the most common internal modification of the eukaryotic mRNA. However, there are no detailed reports on the mA transcriptome map of yak ovary. Therefore, this study aimed to collected the yak ovarian tissues at three different states of anestrus (YO-A), estrus (YO-F), and pregnancy (YO-P), and obtained the full transcriptome mA map in yak by MeRIP-seq.

RESULTS

The HE staining revealed that the number of growing follicles and mature follicles in the ovary during the estrus period was relatively higher than those in the anestrus period and the pregnancy period. The RT-qPCR showed that the expression of METTL3, METTL14, FTO, YTHDC1 were significantly different across different periods in the ovaries, which suggests that mA may play a regulatory role in ovarian activity. Next, we identified 20,174, 19,747 and 13,523 mA peaks in the three ovarian samples of YO-A, YO-F and YO-P using the methylated RNA immunoprecipitation sequencing (MeRIP-seq). The mA peaks are highly enriched in the coding sequence (CDS) region and 3'untranslated region (3'UTR) as well as the conserved sequence of "RRACH." The GO, KEGG and GSEA analysis revealed the involvement of mA in many physiological activities of the yak's ovary during reproductive cycle. The association analysis found that some genes such as BNC1, HOMER1, BMP15, BMP6, GPX3, and WNT11 were related to ovarian functions.

CONCLUSIONS

The comparison of the distribution patterns of methylation peaks in the ovarian tissues across different periods further explored the mA markers related to the regulation of ovarian ovulation and follicular development in the yak ovary. This comprehensive map provides a solid foundation for revealing the potential function of the mRNA mA modification in the yak ovary.