Allele frequencies of intragenic, and 5' and 3' markers of the dystrophin gene in Japanese families afflicted with Duchenne or Becker muscular dystrophy

Intragenic DNA polymorphism analysis of DMD/BMD dystrophy gene for carrier and prenatal diagnosis in 60 Iranian healthy individuals

Duchenne and Becker muscular dystrophies (DMD/BMD) are allelic, x-linked neuromuscular disease resulting from mutations in dystrophin gene. DMD is the most severe and frequent inherited but still incurable disease in males. About two-third of such patients have large deletions or duplications that can be identified by multiplex polymerase chain reaction (PCR). In one-third of remaining cases, a linkage analysis that involves DNA markers of intragenic dystrophic gene is considered a rapid and simple method for carrier detection and prenatal diagnosis. In the present study, we investigated frequency and heterozygosity of three polymorphic restriction sites and also four highly polymorphic (CA)(n) repeat microsatellites loci within hot spots region of human dystrophin gene in 60 healthy Iranian populations. Our findings indicated that the allele frequencies of pERT87-8/TaqI, pERT87-15/BamHI, and pERT87-15/XmnI were 0.23/0.77, 0.221/0.779, and 0.239/0.761, respectively. Among these three polymorphic sites, pERT78-15/XmnI locus had the highest heterozygosity with frequency of 47.17%. We also found that STR49 had the highest heterozygosity among four polymorphic microsatellites. These findings are useful in linkage analysis of Iranian DMD families in both carrier detection and prenatal diagnosis.

Prenatal diagnosis of Duchenne muscular dystrophy in the Japanese population by fluorescent CA repeat polymorphisms analysis

OBJECTIVE

To investigate the efficacy of CA repeat analysis using fluorescence-labeled primers in the prenatal diagnosis of Duchenne muscular dystrophy in the Japanese population.

METHODS

Allelic frequencies of polymorphic loci in the Duchenne muscular dystrophy gene were ascertained, and the polymorphic information content (PIC) was calculated. CA repeat analysis of 21 Japanese families with Duchenne muscular dystrophy was then performed.

RESULTS

The STR 49 locus had the highest PIC, followed in decreasing order by the loci of STR 44, STR 45, STR 50, DYS III, DYS II, DYS I, and 3' CA. The diagnostic applicability increased to 0.999 when the PICs of all 8 loci were combined. When the highest PIC from each of the 5' end, exons near the 3' end and the 3' end were combined, the diagnostic applicability increased to 0.988. Of the 7 males examined prenatally, 1 was diagnosed as normal, and 6 were affected, while of the 9 females examined, 5 were diagnosed as carriers, and 4 as non-carriers.

CONCLUSION

CA repeat analysis using fluorescence-labeled primers is useful in the prenatal diagnosis of Duchenne muscular dystrophy in the Japanese population.