DUX4 and Facioscapulohumeral dystrophy: Validation studies typically identify a gene associated with FSHD and determine if it is a DUX4 target gene, as with PITX1 (Dixit et al, 2007), FRG1 (Ferri et al, 2015), FRG2 (Thijssen et al, 2014) and CRYM (Vanderplanck et al, 2011).