Interestingly, APN+MMSCs isolated from the muscle biopsies of three FSHD1 patients (Table S1) express DUX4 mRNA when primed for muscle differentiation (Fig. 1C), with a pattern of expression analogous to that observed in myoblasts of FSHD patients [18, 49]. Here, DUX4 is linked to Facioscapulohumeral dystrophy.