DUX4 and facioscapulohumeral muscular dystrophy: To determine whether Sunitinib improves myogenic differentiation in human FSHD myoblasts, we obtained clonal cell lines derived from a mosaic FSHD1 individual (Krom et al., 2012): a control clone containing a ‘healthy’ number of D4Z4 repeats (54.6) and a clone containing a pathogenic contraction of D4Z4 units and expressing DUX4 (54.12), thus apart from the number of DUX4 repeats, both have the same genetic background.