FLT3LG and facioscapulohumeral muscular dystrophy: Interestingly, two proposed alternative FSHD candidate genes, FRG1 (FSHD region gene 1) [32] and FRG2 (FSHD region gene 2) [33], localized proximal to the chromosome 4q35 D4Z4 array, were recently identified as direct DUX4-FL target genes [34, 35], thus linking misexpression of these genes to the widely accepted DUX4 model of FSHD [19].