Fibroblasts signal Chorion villi cells No expression Amniocytes of muscle proteins MyoD ↓ myogenin Myf5 Virus-mediated MyoD gene transfer Mef2 Expression of Differentiation into early-myogenesis muscle structural genes myogenic cells proteins:desmin ↓ muscle development B: Further differentiation Expression of into multinucleated late-myogenesis myotubes proteins:titin,myosin and DYSTROPHIN A 20 um MyoD诱导成纤维细胞表现骨骼肌细胞特征MyoD诱导成纤维细胞表现骨骼肌细胞特征