Further studies of gene deletions that cause Duchenne and Becker muscular dystrophies.

Fetal muscle cDNA clones covering at least 11.4 kb of the Duchenne muscular dystrophy (DMD) gene sequence were used to identify a deletion-prone region in DNA from DMD and Becker muscular dystrophy (BMD) patients. Of 36 BMD cases, 17 (47%) had deletions and all of the deletions began in the same intron of the gene. Of 107 DMD patients, 27 (25%) were deleted for this region, and 19 deletions originate in the same intron. Using a cDNA probe for an adjacent region of the gene, 32 new deletions were detected in DMD patients (total 44%). No new BMD deletions were detected. The DMD deletions were very heterogeneous. Thus two cDNA probes covering 2.4 kb could detect 53% of these deletions. Considering the whole locus, DMD and BMD are caused by a deletion of the gene sequence in at least 67% of cases.