MILD DEFICIENCY OF DYSTROPHIN-ASSOCIATED PROTEINS IN BECKER MUSCULAR-DYSTROPHY PATIENTS HAVING IN-FRAME DELETIONS IN THE ROD DOMAIN OF DYSTROPHIN

The dystrophin-glycoprotein complex spans the sarcolemma to provide a linkage between the subsarcolemmal cytoskeleton and the extracellular matrix in skeletal muscle. In Duchenne muscular dystrophy (DMD), the a bsence of dystrophin leads to a drastic reduction in all of the dystro phin-associated proteins in the sarcolemma, thus causing the disruptio n of the dystrophin-glycoprotein complex and the loss of the linkage t o the extracellular matrix. The resulting sarcolemmal instability is p resumed to render muscle fibers susceptible to necrosis. In the presen t study, we investigated the status of the dystrophin-associated prote ins in the skeletal muscle from patients with Becker muscular dystroph y (BMD), a milder allelic form of DMD. BMD patients having in-frame de letions in the rod domain of dystrophin showed a mild to moderate redu ction in all of the dystrophin-associated proteins in the sarcolemma, but this reduction was not as severe as that in DMD patients. The redu ction of the immunostaining for the dystrophin-associated proteins sho wed a good correlation with that for dystrophin in both intensity and distribution. Our results indicate that (1) the abnormality of the sar colemmal glycoprotein complex, which is similar to but milder than tha t in DMD patients, also exists in these BMD patients and (2) the rod d omain of dystrophin is not crucial for the interaction with the dystro phin-associated proteins.