Duchenne muscular dystrophy (DMD) is caused by the defect of dystrophin, and Fukuyama congenital muscular dystrophy (FCMD) is caused by an abnormal fukutin gene leading to the glycosylation defect of alpha-dystroglycan.
We initially present the main clinical and diagnostic data concerning the CMDs related to changes in the complex dystrophin-associated glycoproteins-extracellular matrix: CMD with merosin deficiency (CMD1A), collagen VI related CMDs (Ullrich CMD and Bethlem myopathy), CMDs with abnormal glycosylation of alpha-dystroglycan (Fukuyama CMD, Muscle-eye-brain disease, Walker-Warburg syndrome, CMD1C, CMD1D), and the much rarer CMD with integrin deficiency.
In Fukuyama-type congenital muscular dystrophy (FCMD), the finding of abnormal expression of the dystrophin-associated proteins may provide a clue to its molecular pathogenesis.
To explain the observation of 3/23 FCMD males with abnormal dystrophin, we propose that dystrophin and the FCMD gene product interact and that the earlier onset and greater severity of these patients' phenotype (relative to Duchenne muscular dystrophy) are due to their being heterozygous for the FCMD mutation in addition to being hemizygous for Duchenne muscular dystrophy, a genotype that is predicted to occur in 1/175,000 Japanese males.
Although DNA analysis by Southern blotting with complementary DNAs representing the whole of the dystrophin coding sequence detected neither gross deletions nor duplications, immunohistochemistry and Western blotting of the biopsied skeletal muscle with an antidystrophin monoclonal antibody (dystrophin test) showed that the approximately 400-kd dystrophin was expressed normally at the sarcoplasmic membrane of the FCMD phenotype patient but was completely absent in the DMD phenotype patient.