FRG1 and facioscapulohumeral muscular dystrophy: Since FSHD predominantly affects adult muscles and the human FRG1 gene is a direct transcriptional target of the DUX4-FL protein in FSHD muscle [34], the UAS-DmFRG1 flies were crossed with the DJ667 GAL4 line, which expresses GAL4 predominantly in adult thoracic muscle [77].