Southern blot and PCR analyses of dystrophin gene deletions in Japanese patients with Duchenne muscular dystrophy.

We have analyzed 34 Japanese patients of 31 families with Duchenne muscular dystrophy (DMD) by Southern blot and PCR (polymerase chain reaction) to detect large deletions in the genomic dystrophin gene on the X chromosome. Fifteen families (48%) had various deletions in the dystrophin gene by Southern blot analysis using the dystrophin cDNA probes 1-2a, 2b-3 and 8 which effectively covers the high-risk regions of deletion. Lengths and positions of the gene deletions detected were variable. Although there were no common deletions of exons in the gene of the DMD patients examined with the above cDNA probes, the deletion frequency of each exon was almost the same as the result previously reported in Caucasian DMD patients. The PCR method was also applied to confirm gene deletions in 9 cases from the above 15 families by amplifying 6 different regions of the dystrophin gene. Eight out of 9 DMD cases had gene deletions at the same genomic regions as found by Southern blot analysis. In a single DMD case, the Southern blot analysis indicated the exon 12 deletion, but PCR successfully amplified a 331 bp DNA fragment containing exon 12 and flanking introns. This difference may arise by a large deletion except for the above small 331 bp sequence in the HindIII digests of dystrophin gene.