DUX4 and facioscapulohumeral muscular dystrophy: Decades of work have generated a detailed list of the genes and pathways affected by DUX4 that may underlie FSHD pathophysiology (Geng et al., 2012; Block et al., 2013; Young et al., 2013; Banerji et al., 2015; Feng et al., 2015; Homma et al., 2015; Dmitriev et al., 2016; Shadle et al., 2017).