Expression of the normally repressed transcription factor DUX4 from the final D4Z4 repeat is believed to cause FSHD; and DUX4 knockdown using phosphorodiamidate morpholino antisense oligonucleotides, short inhibitory siRNA, or RNA interference approaches reduces the FSHD atrophic phenotype in vitro and DUX4-induced myopathy in vivo [36,37]. The gene discussed is DUX4; the disease is facioscapulohumeral muscular dystrophy.