Mitochondrial encephalomyopathies

A novel mitochondrial tRNA Arg mutation resulting in an anticodon swap in a patient with mitochondrial encephalomyopathy

We report a mutation in the anticodon of the tRNA(Arg) gene (m.10437 G>A), resulting in an anticodon swap from GCU to ACU, which is the anticodon of tRNA(Trp), in a boy with mitochondrial encephalomyopathy. Enzyme histochemical analysis of muscle tissue and biochemical analysis of isolated muscle mitochondria demonstrated cytochrome c oxidase (COX) deficiency. Restriction fragment length polymorphism analysis showed that 90% of muscle and 82% of urinary epithelium mtDNA harbored the mutation. The mutation was not identified in blood, fibroblasts, hair roots, or buccal epithelial cells and it was absent in the asymptomatic mother, suggesting that it was a de novo mutation. Single-fiber PCR analysis showed that the proportion of mutated mtDNA correlated with enzyme histochemical COX deficiency. This mutation adds to the three previously described disease-causing mutations in tRNA(Arg), but it is the first mutation occurring in the anticodon of tRNA(Arg).

Heart diseases in mitochondrial encephalomyopathy, lactic acidosis, and stroke syndrome

Mitochondrial encephalomyopathy, lactic acidosis, and stroke (MELAS) syndrome is a mitochondrial genetic disorder caused by a point mutation, resulting in the substitution of guanine for adenine at nucleotide 3243 (A3243G) of mitochondrial DNA. This disease is characterized by a multisystem disorder with variable manifestations. The authors review heart involvement in this disease.