It may be that DUX4 levels and/or expression duration in an induced iDUX4 myoblast is higher/longer than in the muscle cell of an FSHD patient, yet DUX4c counteracts both high and residual ‘leaky’ expression of DUX4-target genes. This evidence concerns the gene DUX4L9 and facioscapulohumeral muscular dystrophy.