The striated muscle forming regions in the vertebrate embryo respond to extra-cellular signals emitted from surrounding structures. Subsequently, genetic programs are activated in these tissues; ultimately forming cardiac or skeletal myocytes. P19 are embryonal carcinoma cells that can differentiate into beating myocardium and multi-nucleated skeletal myotubes that are biochemically and physiologically similar to in vivo tissues. MyoD (a member of the Myogenic Regulatory Factors (MRFs)), Sonic Hedgehog (Shh), Gli2 and Meox1 play roles in the commitment of cells into the skeletal muscle...