Abstract
Follicular atresia triggered by granulosa cell (GC) apoptosis severely reduces female fertility and accelerates reproductive aging. GC apoptosis is a complex process regulated by multiple factors, regulatory axes, and signaling pathways. Here, we report a novel, small regulatory network involved in GC apoptosis and follicular atresia. miR-187, a miRNA down-regulated during follicular atresia in sows, maintains TGFBR2 mRNA stability in sow GCs by directly binding to its 5'-UTR. miR-187 activates the transforming growth factor-β (TGF-β) signaling pathway and suppresses GC apoptosis via TGFBR2 activation. NORHA, a pro-apoptotic lncRNA expressed in sow GCs, inhibits TGFBR2-mediated activation of the TGF-β signaling pathway by sponging miR-187. In contrast, NORFA, a functional lncRNA associated with sow follicular atresia and GC apoptosis, enhances miR-187 and TGFBR2 expression by inhibiting NORHA and activating NFIX. Our findings define a simple regulatory network that controls GC apoptosis and follicular atresia, providing new insights into the mechanisms of GC apoptosis, follicular atresia, and female fertility.