PITX1 and facioscapulohumeral muscular dystrophy: Nuclei with the opposite staining pattern (cPARP+/DUX4−) were increased in FSHD myoblasts and might reflect an apoptotic process initiated by a pulse of DUX4 expression, followed by DUX4 protein degradation, similarly to the explanation we proposed above to explain the presence of PITX1+/DUX4− nuclei.