A growing number of reports have revealed that microRNAs (miRNAs) play critical roles in spermatogenesis. Our previous study showed that miR-762 is differentially expressed in immature and mature testes of Large White boars. Our present data shows that miR-762 directly binds the 3′ untranslated region (3′UTR) of ring finger protein 4 (RNF4) and down-regulates RNF4 expression. A single nucleotide polymorphism (SNP) in the RNF4 3′UTR that is significantly associated with porcine sperm quality traits leads to a change in the miR-762 binding ability. Moreover, miR-762 promotes the proliferation of and inhibits apoptosis in porcine immature Sertoli cells, partly by accelerating DNA damage repair and by reducing androgen receptor (AR) expression. Taken together, these findings suggest that miR-762 may play a role in pig spermatogenesis by regulating immature Sertoli cell growth.

Numerous studies have demonstrated that microRNAs (miRNAs) play important roles in cell growth, apoptosis and spermatogenesis. Our previous study showed that miR-638 was differentially expressed in sexually immature and mature testes of Large White boars. Here we reported that sperm-associated antigen 1 (SPAG1) was a direct target gene of miR-638. Moreover, miR-638 inhibited cell proliferation and cell cycle, and promoted apoptosis of porcine immature Sertoli cells. Key genes including phosphorylated phosphatidylinositide 3-kinases (p-PI3K) and phosphorylated serine/ threonine kinase (p-AKT) in PI3K/AKT pathway as well as cell cycle factors including c-MYC, cyclin-D1 (CCND1), cyclin-E1 (CCNE1) and cyclin-dependent kinase 4 (CDK4) were all significantly down-regulated after overexpression of miR-638 or RNAi of SPAG1. Notably, mRNA levels of SRY-related HMG-box 2 (SOX2) and POU domain, class 5, transcription factor 1 (POU5F1) essential for spermatogonia proliferation were significantly suppressed in SPAG1 siRNA- transfected ST cells. This study suggests that miR-638 regulates immature Sertoli cell growth and apoptosis by targeting SPAG1 gene which can indirectly inactivate PI3K/AKT pathway, and plays roles in pig spermatogenesis.