DUX4 and Facioscapulohumeral dystrophy: The levels of LEUTX, a DUX4 target, were lower in the uninduced state (i.e., Dox) than in myotubes from FSHD patients and were highly induced upon Dox treatment (Fig. S1F), which is associated with DUX4 induction (Fig. S1G), demonstrating the low leakiness of the system and confirming the transcriptional activity of DUX4.