Animal models of Duchenne and Becker muscular dystrophy.

Two animal models have been shown to be related to Duchenne and Becker muscular dystrophy at the molecular level. The mdx mouse is characterized by early onset of muscle degeneration and very mild clinical disease. The disease is minimally progressive and fibrosis of muscle is absent. Linkage studies, absence of dystrophin, and reduced levels of message indicate that the mutation in mdx lies in the gene for dystrophin, the gene that is defective in Duchenne and Becker muscular dystrophy. The xmd dog develops lesions that are essentially indistinguishable from those of Duchenne dystrophy, and there is progressive fibrosis and destruction of muscle tissue. Affected dogs develop severe clinical disease. The absence of dystrophin and its message in muscle, and the linkage of RFLPs recognized by Duchenne cDNA probes, indicate that the mutation in the xmd dog lies in the gene for dystrophin. Exploitation of these models should lead to a greater understanding of molecular and cellular events involved in the pathogenesis of Duchenne and Becker muscular dystrophies.