In contrast to DUX4, DUX4c does not cause cell death [13, 23, 27, 29] and is implicated in progression to the FSHD disorganized myotube phenotype in our culture conditions, rather than to the atrophic phenotype caused by DUX4 expression [32]. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.