MicroRNA-451a Regulates Myogenesis by Suppressing SPARC Expression Levels

MicroRNAs (miRNAs) are small noncoding RNAs that critically regulate gene expression. Their abundance and function have been linked to processes such as senescence and aging. In aged monkey muscle, miR-451a and miR-144-3p were highly upregulated compared to young animals. This led us to hypothesize that the miRNAs 451a/144-3p may be involved in muscle differentiation. We found that these miRNAs are downregulated during the differentiation of C2C12 myoblasts. Overexpression of miR-451a, but not miR-144-3p, robustly impeded the differentiation, suggesting an inhibitory role for miR-451a. We further investigated the potential regulatory targets of miR-451a and identified Sparc mRNA, encoding a secreted protein acidic and rich in cysteine (SPARC), which is involved in wound healing and cellular differentiation. Interestingly, we found that miR-451a suppresses Sparc mRNA translation according to the analysis of polysome profile. Our findings show that miR-451a is downregulated in differentiated myoblasts and decreases C2C12 differentiation at least in part by the suppression of SPARC biosynthesis. C2C12 myoblasts were cultured and two time-points, Day 0 and Day 6 of exposure to differentiation medium, were examined by gene expression microarray analysis using five independent experiments per condition.