SMCHD1 and facioscapulohumeral muscular dystrophy: To study the role of epigenetic modifiers in FSHD, we previously crossed D4Z4-2.5 mice with mice haploinsufficient for Smchd1 (Smchd1MommeD1 mice) [18], a genetic constitution mimicking the presence of FSHD1 and FSHD2 in some affected individuals [19].