A transvection effect resulting from a misbalance of chromatin and transcription factors at 4q35 and unrelated loci following the deletion [12] was proposed to explain that the FRG2 mRNA expressed in FSHD myoblasts originated mostly from the homologous FRG2 gene on chromosome 10, not 4 [16]. The gene discussed is FRG2; the disease is facioscapulohumeral muscular dystrophy.