Identification of a one-basepair deletion in exon 6 of the dystrophin gene

The dystrophin gene, located on the X-chromosome, is the largest gene known to date, containing the greatest number of exons (79) identified thus far (Roberts et al., 1993). Mutations in this gene result most commonly in Duchenne muscular dystrophy (DMD) and less frequently in Becker muscular dystrophy (BMD), a clinically less severe form of the disorder. About two-thirds of the mutations are large deletions or duplications. The remaining mutations are thought to be point mutations, or mutations too small to be detected by commonly used techniques. Here, we have analyzed DNA samples from 16 nondeleted patients for small insertion/deletion mutations. Eighteen exons (3, 4, 6, 8, 12, 13, 17, 19, 43, 44, 45, 47, 48, 50, 51, 52, 60, and pm) were amplified by polymerase chain reaction (PCR), using 200 mu M dNTP and 1 mu Ci/12 mu l alpha -32P-dCTP. The amplified segments contain some flanking intron regions for all exons, except exons 52 and 60. The pm product contains the promoter region plus approximately one-fourth of exon 1. The PCR products were resolved on denaturing polyacrylamide gels and detected by autoradiography. Patient 469 was observed to have a one basepair deletion in exon 6.