Title : Heteroplasmy of mtDNA 3243A>G mutation in seven Han Chinese families by pyrosequencing
Presenter : Ailian Du
Shanghai Jiaotong University School of Medicine, China
Objective : To study the heteroplasmy and phenotype correlations of mtDNA 3243A>G mutation in 7 Han Chinese families using restrict fragment length polymorphism (RFLP) and pyrosequencing (Pyro).
Methods : Seven probands were pathologically and genetically diagnosed as mitochondrial diseases with 3243A>G mutation. The clinical phenotypes were studied in 39 maternal family members. 5 were diagnosed as mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), 2 with pure mitochondrial myopathy (MM), 1 with early neuropathy, ataxia, and retinitis pigmentosa (NARP) syndrome. Six with diabetes, 3 with hearing loss, and 20 family members are normal. Blood DNA from 37 members were detected with RFLP and pyrosequencing. mtDNA 3243A>G heterogeneity were analyzed.
Results: Mutation load in blood of 5 MELAS patients were 15.7% by RFLP (29% by Pyro), 12.8% (19% by Pyro), 40.1% (53% by Pyro), 25.8% (30% by Pyro), 28.3% (59% by Pyro). Mutation load in 2 MM patients were 13.7% (29% by Pyro) and 76.8% (79% by Pyro), and that in the NARP patient was 20.0% (57% by Pyro). Six family members with diabetes were range from 3.7%-7.6% (0%-14% by Pyro). Three family members with hearing loss were range from 4%-18.2% (6%-18%). The mutation load of 14 normal family members range from 2% to 12.5% (0%-5% by Pyro). Detection by Pyro is more accurate than RFLP when mutation load is lower than 10%. The mutation load is higher in those earlier age of onset.
Conclusion: Pyrosequencing is more reliable when mutation load is lower than 10%. The mutation load is negatively correlate to the age of onset in this research.