miRNA sequencing reveals hypothalamic microRNAs associated with seasonal reproduction in Sunite sheep

The hypothalamus plays a vital role in reproductive processes. Previous studies have identified hypothalamic miRNAs involved in mammalian reproduction, but the miRNA profiles induced by photoperiod changes remain unclear. In this study, we investigated the effects of photoperiod on hypothalamic microRNA (miRNA) regulation by analyzing miRNA expression patterns in Sunite sheep under three different photoperiod conditions-short photoperiod (SP), short-to-long photoperiod transition (SLP), and long photoperiod (LP) -with three biological replicates per group, using miRNA-sequencing technology. A total of 57, 47, and 12 differentially expressed miRNAs (DEMs) were revealed between SP vs. LP, SP vs. SLP, and LP vs. SLP, respectively. We constructed a co-expression network of DEMs and their target genes, identified oar-miR-370-5p, oar-miR-10b, and oar-miR-3957-3p as the miRNAs with the highest numbers of predicted target mRNAs based on interaction analysis. Functional annotation analysis demonstrated that the target genes of DEMs were enriched in multiple KEGG pathways, among which the most significant pathways associated with reproduction included the GnRH signaling pathway, prolactin signaling pathway, VEGF signaling pathway, and Wnt signaling pathway. These findings elucidate the dynamic changes in hypothalamic miRNA expression under varying photoperiods and provide crucial insights into the molecular mechanisms of underlying seasonal estrus in sheep, laying a foundation for future functional validation studies.