The initial lack of evidence for active transcription of DUX4, encoded in each D4Z4 repeat unit, shifted the focus to genes immediately centromeric to the array, like FRG1 and FRG2. Although FRG1 overexpression in mice leads to a dystrophic phenotype, its deregulation in muscles of FSHD patients has not been consistently demonstrated[19,27,28,31-34,36-40]. Here, DUX4 is linked to facioscapulohumeral muscular dystrophy.