A 424-residue DUX4 protein of 52-kDa apparent molecular weight (MW) was later confirmed as the form expressed from the ORF; endogenous DUX4 in FSHD muscle cells appears slightly larger [19,20,21,22] most probably because of post-translational modifications. This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.