DUX4 and facioscapulohumeral muscular dystrophy: In FSHD muscles, DUX4 expression is linked to the loss of repressive epigenetic marks and DNA hypomethylation of the D4Z4 repeats located on sub-telomeric part of the chromosome 4 (van Overveld et al., 2003; Zeng et al., 2009; Jones et al., 2015; Salsi et al., 2020) and to the presence of myogenic enhancers interacting with the DUX4 promoter (Himeda et al., 2014).