miR-638 Inhibits immature Sertoli cell growth by indirectly inactivating PI3K/AKT pathway via SPAG1 gene

<p>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 (<i>SPAG1</i>) 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 <i>SPAG1</i>. Notably, mRNA levels of SRY-related HMG-box 2 (<i>SOX2)</i> and POU domain, class 5, transcription factor 1 (<i>POU5F1)</i> essential for spermatogonia proliferation were significantly suppressed in <i>SPAG1</i> siRNA- transfected ST cells. This study suggests that miR-638 regulates immature Sertoli cell growth and apoptosis by targeting <i>SPAG1</i> gene which can indirectly inactivate PI3K/AKT pathway, and plays roles in pig spermatogenesis.</p>