PHENOTYPIC AND PATHOLOGICAL EVALUATION OF THE MYD MOUSE, A CANDIDATE MODEL FOR FACIOSCAPULOHUMERAL DYSTROPHY

Facioscapulohumeral dystrophy (FSHD) is an autosomal dominant disease of unknown pathogenesis which is characterized by weakness of the face and shoulder girdle. It is associated with a sensorineural hearing lo ss which may be subclinical. FSHD has been mapped to the distalmost po rtion of 4q35, although the gene has not yet been identified. Distal 4 q has homology with a region of mouse chromosome 8 to which a mouse mu tant, myodyslrophy (myd), has been mapped. Muscle from homozygotes for the myd mutation appears dystrophic, showing degenerating and regener ating fibers, inflammatory infiltrates, central nuclei, and variation in fiber size. Brainstem auditory evoked potentials reveal a sensorine ural hearing loss in myd homozygotes. Based on the homologous genetic map locations, and the phenotypic syndrome of dystrophic muscle with s ensorineural hearing loss, we suggest that myd represents an animal mo del for the human disease FSHD.