A CYSTEINE-3340 SUBSTITUTION IN THE DYSTROGLYCAN-BINDING DOMAIN OF DYSTROPHIN-ASSOCIATED WITH DUCHENNE MUSCULAR-DYSTROPHY, MENTAL-RETARDATION AND ABSENCE OF THE ERG B-WAVE

We report the first C-terminal missense mutation in a Duchenne muscula r dystrophy patient, A G10227A transition of the dystrophin gene was f ound which resulted in the substitution of a highly conserved cysteine at position 3340 within the second half of the dystroglycan-binding d omain. Residual amounts of 427 kDa dystrophin were detected in western blot analysis of the patient's muscle tissue, and immunohistological examination revealed weak traces of dystrophin on all fibers. Sarcolem mal staining intensity of 43 kDa beta-dystroglycan was also reduced, M ental retardation in our patient and absence of the b-wave in his elec troretinogram indicate that central nervous functions of dystrophin is oforms also depend on the presence of cysteine 3340.