DUX4 and facioscapulohumeral muscular dystrophy: In humans, these consist of the three paralogues DUXA, DUXB and DUX4 [10], of which only DUX4 has been extensively characterised due to its roles in facioscapulohumeral muscular dystrophy (FSHD) [11] and multiple cancers [1, 12, 13].