DUX4 and facioscapulohumeral muscular dystrophy: Additional evidence for DUX4-initiated DNA damage came from work showing increased numbers of TUNEL-positive nuclei (a marker for DNA fragmentation) in FSHD patient muscles and upon DUX4-FL expression in model systems (Hauerslev et al., 2013; Sandri et al., 2001; Statland et al., 2015; Wallace et al., 2011; Wuebbles et al., 2010).