CircRNA profiling reveals circSMC1B that promotes bovine male germline stem cells proliferation and apoptosis via sponging let-7i.

BACKGROUND: Despite significant advancements in artificial insemination techniques, male reproduction continues to pose a considerable challenge in cattle breeding. Circular RNAs (circRNAs), a class of non-coding RNAs (ncRNAs), play a crucial role in regulating testis growth and spermatogenesis. Therefore, it is essential to comprehend the involvement of circRNAs in bull reproduction for livestock production. However, the identification of differentially expressed circRNAs during testis development and their underlying mechanisms remains largely unknown. RESULTS: In this study, RNA-seq was employed to investigate the expression of circRNAs in neonatal and sexually mature bovine testes. We identified 28,065 candidate circRNAs, of which 987 circRNAs showed differential expression between the two stages (P-adjust < 0.05). Notably, circSMC1B was significantly up-regulated in sexually mature testis. Overexpression of circSMC1B promoted the proliferation and apoptosis of bovine male germline stem cells (mGSCs). Further analysis revealed that circSMC1B acts as a molecular sponge for let-7i, while High mobility group AT-hook 1/Nuclear receptor subfamily 6 group A member 1 (HMGA1/NR6 A1) were identified as direct targets of let-7i. Furthermore, circSMC1B levels exhibited a significant positive correlation with HMGA1/NR6A1 mRNA expression in bovine mGSCs, highlighting the critical role of competing endogenous RNA (ceRNA) mechanisms. CONCLUSION: Our research elucidates that circSMC1B, through let-7i binding, promotes bovine mGSCs proliferation and apoptosis by targeting HMGA1/NR6A1. These findings provide valuable resources for studying the functional aspects of circRNAs in testis development and enhance our understanding of the biological function of circSMC1B in promoting bull spermatogenesis.