DUX4L9 and facioscapulohumeral muscular dystrophy: Although FRG2 was consistently reported to be overexpressed from chromosomes 4 and 10 in FSHD muscle [41,44,48], its involvement in FSHD was challenged by the identification of an FSHD1 family in which the deletion not only involved the D4Z4 repeat array, but also eliminated FRG2 and DUX4C from the disease allele [44,47,50,53].