oar-miR-411a-5p Promotes Proliferation and Differentiation in Hu Sheep Myoblasts Under Heat Stress by Targeting SMAD2.

MicroRNAs (miRNAs) are endogenous noncoding RNAs that produce a remarked effect on regulating posttranscriptional gene expression. Our previous study identified a decrease in the expression of oar-miR-411a-5p from umbilical plasma in intrauterine growth restriction (IUGR) Hu lambs subjected to maternal heat stress. In this study, we demonstrated that oar-miR-411a-5p could modulate skeletal muscle development. Overexpression of oar-miR-411a-5p significantly enhanced proliferation and differentiation in heat-stressed Hu sheep myoblasts while suppressing apoptosis. Conversely, inhibition of oar-miR-411a-5p resulted in opposing effects. Subsequently, RNAhybrid analysis revealed targeted sites between oar-miR-411a-5p and the 3' untranslated region (UTR) of SMAD2. This suggested that SMAD2 is a direct target gene of oar-miR-411a-5p, as its expression was negatively modulated by oar-miR-411a-5p, a finding corroborated by dual-luciferase assay and RT-qPCR. Furthermore, co-transfection of oar-miR-411a-5p and SMAD2 into Hu sheep myoblasts indicated that oar-miR-411a-5p modulated heat-stressed myoblast growth by targeting SMAD2. In conclusion, these findings elucidate the function of oar-miR-411a-5p in promoting the development of heat-stressed Hu sheep myoblasts, thereby enhancing our understanding of how miRNAs influence skeletal muscle growth in heat-stressed Hu sheep.