A new approach to gene diagnosis of Duchenne/Becker muscular dystrophy--amplified fragment length polymorphisms.

Four (CA)n repeats, located in introns 44, 45, 49 and 50 of the dystrophin gene, were evaluated in Chinese. These loci are highly polymorphic, with polymorphism information contents of 0.872, 0.772, 0.870 and 0.718, respectively. All four loci can be easily amplified and labelled using two duplex PCR reactions with alpha-32P-dCTP and can be detected by denaturing polyacrylamide gel electrophoresis. Using these four loci and the two polymorphic (CA)n repeats located at the 5' and 3' ends of the dystrophin gene, we have developed a new PCR-based procedure--Amp-FLP (amplified fragment length polymorphism) linkage analysis for the gene diagnosis of DMD/BMD. This method can detect intragenic recombination rapidly and efficiently and greatly improves the success rate of carrier detection and prenatal diagnosis in non-deletion DMD/BMD families. All of the loci used in this procedure are intragenic. In addition, the loci in introns 44, 45, 49 and 50 are located in the deletion-prone region of the dystrophin gene, making them valuable and useful in the identification of deletion mutations. Here we report one case of deletion detection using these four loci.