Localization of the region homologous to the Duchenne muscular dystrophy locus on the mouse X chromosome

Recent progress has resulted in part of the gene mutated in Duchenne and the milder Becker muscular dystrophies being cloned1–3 and has suggested that the gene itself extends over 1,000 to 2,000 kilobases (kb) (ref. 4). To study how mutations in this gene affect muscle development and integrity, it would be of interest to have available a mouse model of the human disease. The mouse mdx mutation affects muscle and confers a mild dystrophic syndrome, but it is not clear whether this mutation is equivalent to Duchenne/Becker muscular dystrophy in man5. Here we describe the use of two sequences from the human Duchenne muscular dystrophy (DMD) gene that cross-hybridize to mouse X-linked sequences to localize the gene homologous to DMD in the mouse. Both sequences map to the region of 10 centimorgan lying between the Tabby (Ta) and Stl4-l (DxPas8) loci, close to the phosphory-lase b kinase locus (Phk). By analogy with the human X-chromosome, we conclude that the region in the mouse around the G6pd and Stl4-l loci may contain two genes corresponding to distinct human myopathies: Emery Dreifuss muscular dystrophy which is known to be closely linked to Stl4-l in man6,7 and the DMD homologue described here.