We initially described iP300w as an effective inactivator of DUX4, a pioneer transcriptional factor that recruits P300/CBP through its C-terminal domain and plays a key role in early embryonic development and facioscapulohumeral muscular dystrophy (FSHD) [31, 32]. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.