Abbreviations  bHLH: basic helix-loop-helix - BSA: bovine serum albumin - CK: creatine kinase - DMEM : Dulbecco’s modified Eagle’s medium - DMSO: dimethyl sulfoxide - DPBS: Dulbecco’s modified phosphate-buffered saline - (E)MEM: Eagle’s minimum essential medium - EDTA: ethylenediaminetetraacetic acid - EGF: epidermal growth factor - FACS: Fluorescence activated cell sorter - FCS: fetal calf serum; FGF: fibroblast growth factor - FITC: fluorescein isothiocyanate - Ig: immunoglobulin - IGF: insulin-like growth factor - NCAM: neural cell adhesion molecule