[Detection of the CAG trinucleotide repeats of MJD1 gene by recombinant DNA technology].

Objective: To establish a stable, accurate and intuitive method for detecting the CAG trinucleotide repeats of MJD1 gene.
Methods: The CAG trinucleotide polymorphism of the MJD1 gene was analyzed by recombinant DNA technology and DNA sequencing in 35 spinocerebellar ataxia 3/Machado-Joseph disease (SCA3/MJD) patients from Mainland China.
Results: The range of the CAG repeat of the 35 patients was 65-81 (mean = 72.96 +/- 4.24). The CAG repeats contained two CAAs and one AAG variations in the CAG motif in all the patients and majority of the healthy controls. There was a CGG/GGG polymorphism at the 3' end of the CAG repeat. The GGG allele was consistently associated with smaller CAG repeats in healthy controls. On the other hand, the CGG allele consistently existed in the patients.
Conclusion: Recombinant DNA technology can stably, accurately and intuitively detect the CAG trinucleotide repeat of the MJD1 gene. It should be used as a major technique to diagnose the SCA3/MJD and analyze the polymorphism of CAG sequence.