Mitochondrial DNA mutations in cardiomyopathy

Mitochondria have their own DNA, 16,569 base pairs, which encodes mRNA genes for 13 subunits of four complexes of the oxidative phosphorylation system, 22 tRNAs required for translation of their mRNA, and two rRNA [1]. The mutation rate in mitochondrial DNA (mtDNA) is more than 10 times higher than that of nuclear DNA [2]. This is due to absence of introns, lack of DNA-binding proteins such as histones, simple DNA repair mechanism, and constant exposure to active oxygen. Mitochondria occupy a pivotal position in cellular energy metabolism, and deterioration of various enzymes linked with energy metabolism in mitochondria due to mtDNA mutations has been shown to be involved in the case of mitochondrial cytopathy or mitochondrial myopathy [3,4,5]. Using advanced gene technology, we have developed rapid and accurate methods for the detection of mutations of mtDNA and total sequences of mtDNA. We review: (1) mtDNA mutations in cardiomyocytes of patients with dilated or hypertrophic cardiomyopathy, (2) a patient with hypertrophic cardiomyopathy associated with left ventricular dilatation, (3) a patient with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) showing hypertrophic cardiomyopathy, and (4) a patient with fatal infantile cardiomyopathy.