Mir-23 Expression In Mouse Skeletal Muscle And Its Role In Regulating Skeletal Muscle Regeneration Preliminary Study

The development of vertebrate skeletal muscle tissues begins from embryonic muscle progenitor cells and then muscle stem cells, myoblasts until myotube formation and muscle fiber maturity. Numerous genes, including growth factors and transcription factors have been identified to participate in this process. Recently, microRNAs (miRNAs) are reported to finely regulate the development of skeletal muscle, this made muscle development more complex and sophisticated.microRNAs are 20-22 nucleotides long and inhibit translation or promote mRNA degradation by annealing to complementary sequences in the 3'untranslated region of specific target mRNAs. We found through bioinformatics that there are pairing sequences of the seed sequence of miRNA-23 in the 3'-UTR fragments of the mRNAs of the three myosin heavy chain gene (Myh1, Myh2 and Myh4). MiR-23 have two substypes, encoding by different genes, they are miR-23a and miR-23b and have one nucleotide different, then we examine miR-23 expression pattern in skeletal muscle and analyze its preliminary function in skeletal muscle regeneration.Firstly, we use real-time RT-PCR to detect miR-23 expression pattern in different periods of mouse, The results showed that miR-23 express high level in skeletal muscle and slow skeletal muscle, with muscle maturation its level increased and reached peak at adult stage.Secondly, C2C12 myoblasts can be induced to terminal differentiate to myotubes. We examined the expression of mature miRNA-23 in C2C12 cells during the differentiate process by real time RT-PCR. There was a low level of miRNA-23 at the initial of differentiation, upon C2C12 myoblast differentiation, miRNA-23 expression reduced, and then dramatically elevated at the end of induction when the myotubes were well-formed, suggesting that miRNA-23 may negatively regulate the differentiation of C2C12 cells.Thirdly, we use bupivacaine to damage mouse quadriceps and research the role of miR-23a in regeneration muscle. The results showed in regenetation skeletal muscle, the protein of Myh1 and Myh2 decreased, However, the mRNA levels of Myh were not declined. The above data suggests that miRNA-23a regulates the expression of myosin heavy chain at translation but transcription level.In conclusion, our data showed that miR-23 expression change with skeletal muscle development and inhibit the expression of myosin heavy chain at translation level. The results of this study suggest, microRNA in muscle development, can affect the expression of muscle structural proteins to regulate muscle development.