DUX4 and facioscapulohumeral muscular dystrophy: In an interesting link with a human disease, it has been recently reported that increased expression of the double homeobox transcription factor DUX4, which is observed in patients with the muscular dystrophy, Facioscapulohumeral muscular dystrophy (FSHD), triggers proteolytic degradation of UPF1, leading to pronounced NMD inhibition.