Although losmapimod and other p38 inhibitors have been shown to repress endogenous DUX4 expression in FSHD muscle cells [50, 51], the necessary targets of the p38 pathway that contribute to DUX4 expression have not been elucidated, and our reporter system indicates that p38 pathway members may modulate expression through D4Z4-S5. Here, DUX4 is linked to Facioscapulohumeral dystrophy.