Complementary DNA clones were isolated that represent the 5' terminal 2.5 kilobases of the murine Duchenne muscular dystrophy (Dmd) messenger RNA (mRNA). Mouse Dmd mRNA was detectable in skeletal and cardiac muscle and at a level approximately 90 percent lower in brain. Dmd mRNA is also present, but at much lower than normal levels, in both the muscle and brain of three different strains of dystrophic mdx mice. The identification of Dmd mRNA in brain raises the possibility of a relation between human Duchenne muscular dystrophy (DMD) gene expression and the mental retardation found in some DMD males. These results also provide evidence that the mdx mutations are allelic variants of mouse Dmd gene mutations.

We have isolated and characterized cDNA clones for the y subunit of mouse muscle phosphorylase kinase

The murine locus corresponding to the human Duchenne/Becker muscular dystrophy (DMD) gene has been regionally mapped on the mouse X chromosome by hybridizing DNA from interspecies mouse crosses with a cDNA clone for the mouse Dmd gene. The results demonstrate that the relative organization of genes on the murine and human X chromosomes is more divergent than has previously been postulated. Furthermore, the mouse Dmd gene maps to a similar region of the X chromosome as does the mouse muscular dystrophy mutation mdx, providing further evidence that the mdx mutant may be a murine equivalent of human DMD. However, Southern analysis of portions of the mouse Dmd gene has not yet revealed any differences between mdx and wild-type mice.