MiR-424 induce buffalo (Bubalus bubalis) follicular atresia via targeting and inhibiting SERPINB2

Apoptosis of mammalian granulosa cells (GCs) is considered to be the main cause of follicular atresia. MiRNA-mediated post-transcriptional gene regulation plays a pivotal role in cell apoptosis. Our previous studies demonstrated that miR-424 is highly expressed in atretic follicles and may promoter of buffalo follicular atresia. In this study, we investigated the role and molecular mechanisms of miR-424 in buffalo follicular atresia. GCs apoptosis, proliferation and estrogen secretion were assessed by flow cytometry, EdU and ELISA, respectively. The expression levels of relevant genes were measured by qRT-PCR. Last, miR-424 agomir and antagomir was administered to mice via tail vein injection. The results showed that miR-424 promotes follicular atresia by inducing cell cycle arrest, inhibiting GC proliferation, suppressing the secretion of estradiol, and enhancing apoptosis. SERPINB2, as a target gene of miR-424, inhibits follicular atresia by promoting GCs proliferation, hormone secretion and inhibiting GCs apoptosis. Overexpression of miR-424 or silencing of SERPINB2 significantly reduced the number of follicles at various developmental stages in mice, whereas inhibition of miR-424 yielded opposite effects. In conclusion, our findings establish miR-424 as a key regulator of follicular atresia in buffalo, through direct targeting of SERPINB2 to modulate granulosa cell functions.