Gene deletions in Japanese patients with Duchenne and Becker muscular dystrophies: deletion study and carrier detection.

Fifty unrelated Japanese patients with Duchenne and Becker muscular dystrophy (DMD and BMD) have been studied through use of the dystrophin cDNA probes. The 14-kb dystrophin cDNA was subdivided into six subclones, and Hind III-digested DNAs were analyzed by Southern blotting. Of 50 unrelated patients, 20 showed a deletion of one or several of the exon-containing Hind III fragments (40.0%). These corresponded to 50% (11/22) of BMD patients and 32.1% (9/28) of DMD patients, and the position and extent of deletions were mapped and proven to be more heterogeneous in DMD than in BMD. Both ends of deletions detected by probe 1-2a were common to all six BMD patients, and the 5' ends of deletions in probe 5b-7 were also common to four BMD patients. The phenotypic-specific deletion in Japanese BMD patients existed in the 5' end of the DMD gene, although an apparently similar deletion produced a wide range of clinical courses (BMD phenotype). Three out of eight females in DMD/BMD families were diagnosed as carriers through use of the junctional fragment and dosage analyses of dystrophin cDNA.