Conversely, the D4Z4 arrays on chromosomes 3, 13, 14, 15, 21, 22, and the Y chromosome, which are not epigenetically dysregulated in either form of FSHD, have 30–60 nucleotide variants per RU just in the ~500 bp region corresponding to their putative DUX4 ORFs, and 70% of those variants are C/G to A/T transitions, thus eliminating potential methylation sites [23]. The gene discussed is DUX4; the disease is facioscapulohumeral muscular dystrophy.