Comparison of mitochondrial DNA polymorphism between Chinese subjects and patients with mitochondrial myopathy

Mitochondrial myopathies are a clinically and biochemically heterogeneous group of disorders sharing common features characterized by structural and functional abnormalities of the mitochondria in skeletal muscle biopsy of the patients. The genetic defects in some of the mitochondrial diseases have been reported recently. However, the mechanisms of pathogenesis of these disorders are still obscure. It has been hypothesized by Morgan-Hughes that there is an increased frequency of DNA polymorphism in the noncoding region of the mitochondrial genome in patients with mitochondriopathy. In this study, we analyzed the mtDNAs isolated from 62 healthy Chinese subjects and 34 blood samples of patients with various mitochondrial myopathies to search for disease-associated RFLPs by PCR technique and restriction pattern analysis. A comparison of the frequency of RFLPs in mtDNAs between normal Chinese subjects and patients was done by statistical analysis. Five new polymorphic sites in mtDNAs from patients were revealed by restriction endonucleases AluI, HaeIII, HinfI, and EcoRII, respectively. These results showed that the frequency of RFLPs in mtDNA increased in patients with mitochondriopathies. Although these results are in line with the hypothesis of Morgan-Hughes, we analyzed only 8.9% of the nucleotide sequence of human mtDNA. Further test of the hypothesis with more detailed analysis of mtDNAs from more patients and larger normal population size is warranted.