Epigenetic Regulation of miR-25 and Lnc107153 on Expression of Seasonal Estrus Key Gene CHGA in Sheep

SIMPLE SUMMARY: In sheep pituitary pars tuberalis tissue, EYA3, TSHβ and CHGA are key genes regulating seasonal reproduction. Their high expression is the characteristic signal under long photoperiods (EYA3, TSHβ) and short photoperiods (CHGA). The epigenetic regulation of microRNAs and LncRNAs on their expression remains unknown. In this study, our results indicated that miR-25 could inhibit the expression of CHGA by specifically binding to its 3′UTR region in pituitary cells. Lnc107153 played the role of CeRNA, which can adsorb miR-25 and weaken the inhibitory effect of miR-25 on CHGA expression. Together, these results suggested the epigenetic regulative network of Lnc107153-miR-25-CHGA was involved in sheep seasonal reproduction. ABSTRACT: Pituitary pars tuberalis (PT) plays an important role as the transmission center in the seasonal reproduction of animals. It helps convert external photoperiod signals into intrinsic seasonal reproduction signals. In sheep PT, specific expression patterns of several genes (including short photoperiod-induced gene CHGA and long photoperiod genes EYA3 and TSHβ) under different photoperiods are crucial characteristics during this signal transduction. Recent studies have revealed the role of epigenetics in regulating the expression of seasonal reproductive key genes. Therefore, we explored whether microRNAs and LncRNAs regulated the expressions of the above key genes. Firstly, the expression of miR-25 and CHGA showed a significant negative correlation in sheep PT. Results of the dual luciferase reporter assay and miR-25 overexpression indicated that miR-25 could inhibit the expression of CHGA by specifically binding to its 3′UTR region in pituitary cells. Then, expression negative correlation and dual luciferase reporter analyses were used to screen and identify the candidate LncRNA (Lnc107153) targeted by miR-25. Finally, the results of fluorescence in situ hybridization and Lnc107153 overexpression suggested that Lnc107153 and miR-25 were involved in the epigenetic regulation of CHGA expression. However, the expressions of EYA3 and TSHβ were not regulated by miRNAs. These results will provide new insights into the epigenetic regulatory network of key genes in sheep seasonal reproduction.