骨骼肌干细胞激活、增殖、分化调控机理研究不仅为理解成体干细胞的生物学功能提供理论基础，而且在临床再生医学中具有重要的应用价值。申请者实验室多年从事Myostatin和非编码RNA在肌肉发育与再生中功能与分子机制研究。Myostatin是骨骼肌干细胞负调控因子，前期研究利用 Myostatin基因敲除鼠为材料，我们筛选到若干受Myostatin调控的miRNA，其中一个受Myostatin调控的miR-A影响骨骼肌干细胞分化，我们已制备了miR-A的转基因和敲除鼠。本项目的科学问题是,利用miR-A转基因和敲除鼠为材料,深入研究miR-A在骨骼肌干细胞激活、增殖与分化中的功能与分子机制。我们观察到一个十分有趣的现象，既无论过表达或敲低表达miR-A都可以促进骨骼肌细胞分化。因此，本研究期望通过揭示miR-A这一有趣现象的分子机制，为深入理解miRNA发挥功能的新分子机理提供理论依据。

Adult stem cells play important roles in the organ growth and regeneration during postnatal development. Adult skeletal muscle stem cells, also known satellite cells, are major contributors to the maintenance and repair of postnatal skeletal muscle tissue. In uninjured muscle, satellite cells reside in a quiescent state, while in damaged muscle satellite cells re-enter to cell cycle and cycling satellite cells undergo differentiation and fuse to damaged myofibers during muscle regeneration. Therefore, the investigation of the molecular mechanism underling the activation, proliferation and differentiation of skeletal muscle satellite cells would not only help us understand biological function of adult stem cells but also have significantly clinical relevance for regenerative medicine. Our lab is focusing on functional studies of non-protein coding RNAs during activation, proliferation and differentiation of satellite cells. Myostatin, a cytokine predominantly expressed in skeletal muscle, functions as an inhibitor of activation, proliferation and differentiation of satellite cells. We have recently identified several myostatin-regulated miRNAs through miRNA transcriptome comparison between myostatin knockout and wild type mice. Those miRNAs are predominantly expressed in skeletal muscle and our data indicate that miR-A may have important function in the differentiation of satellite cells during muscle regeneration. Interestingly, we found that either overexpression or knockdown of miR-A promotes C2C12 cell differentiation. In order to investigate the functional roles of the miRNA in vivo, we have already generated knockout and transgenic mice and phenotypic analysis of those mice indicate critical roles of miR-A during muscle development and regeneration. In this project, we propose that we will investigate the function of miR-A on activation, proliferation and differentiation of satellite cells using miR-A transgenic and knockout mice in vivo. Then we will decipher the molecular mechnism of miR-A function, expecially the mechanism of transcriptional regulation of miRNAs during activation, proliferation and differentiation of satellite cells and muscle regeneration.