Alternatively, DUX4 expression can be observed in cultured human myocytes but DUX4 protein from endogenous DUX4 genes in their arrayed context on chromosome 4 is present in 0.5 to 4.3% of cultured differentiated FSHD myocytes with variability seen between individuals [15, 22]. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.