As the homeodomains of DUX4 fall within the paired homeodomain class, and indeed are very close in sequence to those of the skeletal muscle stem cell regulators Pax3 and Pax7 [24, 25], a model suggesting that skeletal myogenic phenotypes in FSHD may be due in part to competition with Pax3/7 for targets was proposed [22]. This evidence concerns the gene PAX3 and facioscapulohumeral muscular dystrophy.