Taken together, the location of the human FAT1 gene next to the critical FSHD locus at 4q35, the similarity between the Fat1-dependent muscles and those affected in FSHD, and the appearance in Fat1 mutants of non-muscle features of FSHD, suggest a possible role of FAT1 in the pathophysiology of this disease. The gene discussed is FAT1; the disease is facioscapulohumeral muscular dystrophy.