DUX4 and facioscapulohumeral muscular dystrophy: However, immunostaining revealed mosaic DUX4-FL protein expression in the myonuclei (Fig 10I–10L), reminiscent of the sporadic natural bursting of expression seen in FSHD myonuclei, and three downstream target genes, Wfdc3, Trim36, and Cxcr4 (Fig 9B–9D), were greatly induced by TMX in the skeletal muscles of ACTA1-MCM;FLExDUX4 mice.