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  • Title: Accumulation of somatic nucleotide substitutions in mitochondrial DNA associated with the 3243 A-to-G tRNA(leu)(UUR) mutation in encephalomyopathy and cardiomyopathy.
    Author: Kovalenko SA, Tanaka M, Yoneda M, Iakovlev AF, Ozawa T.
    Journal: Biochem Biophys Res Commun; 1996 May 15; 222(2):201-7. PubMed ID: 8670183.
    Abstract:
    To understand the pathogenesis of mitochondrial encephalomyopathy and cardiomyopathy, we analyzed the sequence heterogeneity of the skeletal muscle mitochondrial DNA from a patient with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS). A mtDNA segment of 347 bp amplified from the total DNA was cloned into a vector. Analysis of 60 independent clones (20,800 bp in total) revealed the 3243 A-->G transition in all the sequenced clones and additional nucleotide substitutions at 5 sites in 10 clones. The frequency of mutant clones (10/60) in the MELAS patient was significantly higher [chi2 = 10.909, P < 0.05] than that in an age-matched skeletal muscle control (0/60) as well as in a normal placenta (2/60). These results support our hypothesis that secondary somatic mtDNA mutations can be initiated by the 3243 A-->G mutation and that the accumulation of somatic mutation in individuals with deleterious inherited mitochondrial genotype can contribute to the progressive mitochondrial dysfunction in MELAS.
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