The DUX4 protein has been observed by immunostaining of cultured FSHD myoblasts, which show infrequent, possibly episodic, expression (Jones et al., 2012; Snider et al., 2010), and differentiated myotubes, which show more prevalent expression (Block et al., 2013; Rickard et al., 2015). The gene discussed is DUX4; the disease is facioscapulohumeral muscular dystrophy.