Dysferlin is a surface membrane-associated protein that is absent in Miyoshi myopathy

Recently we reported that mutations in a muscle protein "dysferlin" are present in limb girdle muscular dystrophy-2B and a related, adult-onset, distal dystrophy known as Miyoshi myopathy (MM). We report that antibodies to dysferlin identify a protein of approximately 230 kDa and show that dysferlin is located in the muscle membrane. This protein is absent in MM and LGMD-2B muscle. By contrast, dystrophin and other dystrophin-associated proteins are normal in these patients. Thus, dysferlin is a membrane-associated protein that is not likely to be an integral component of the dystrophin complex. Although it is not essential for initial myogenesis, it appears to be critical for sustained normal function in mature muscle.