MYF5 and facioscapulohumeral muscular dystrophy: The good growth and efficient differentiation to myotubes of FSHD myoblasts observed by us and others [15] are consistent with our finding that the myogenic regulatory factors MYOD1, MYOG, MYF5, and MYF6 were equally highly expressed at the RNA level in FSHD vs. control myoblasts and only MYF6 was significantly downregulated in FSHD vs. control myotubes.