DUX4 and Facioscapulohumeral dystrophy: This model is based on the inefficient epigenetic repression of the DUX4 retrogene in the D4Z4 macrosattelite repeat adjacent to a polymorphic poly-adenylation sequence in the subtelomeric region of chromosome 4, and results in variegated expression of DUX4 in skeletal muscle nuclei in FSHD.