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Increased mitochondrial DNA in blood vessels and ragged-red fibers in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). 1993

M Tokunaga, and S Mita, and R Sakuta, and I Nonaka, and S Araki
First Department of Internal Medicine, Kumamoto University School of Medicine, Japan.

Using in situ hybridization, we studied muscle biopsy specimens from 4 patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Three of the 4 patients with MELAS had a mutation at position 3243 of mitochondrial DNA (mtDNA) in the transfer RNALeu(UUR) gene, and the other patient had a mutation at position 3271 in the same transfer RNALeu(UUR) gene. Quantitative analysis using Southern blot hybridization and polymerase chain reaction showed 80 to 90% mutant mtDNA in muscle. In situ hybridization analysis showed that total mtDNAs (both normal and mutant) were extremely increased in blood vessels with high succinate dehydrogenase activity (strongly succinate dehydrogenase-reactive blood vessels) and ragged-red fibers. Cytochrome c oxidase activity in most of these reactive blood vessels and ragged-red fibers was positive. The similar morphological behavior in these vessels and fibers suggests that an increase in mutant mtDNA is responsible for mitochondrial proliferation and dysfunction in both tissues where cytochrome c oxidase is not a primarily defective enzyme. The pattern of expression of genes for mtDNA-encoded ribosomal RNA and the protein-coding region cytochrome c oxidase subunit II were similar in muscle specimens of patients with MELAS, patients with chronic progressive external ophthalmoplegia, and normal control subjects, and also between the two MELAS mutations. These results do not support the hypothesis that impaired transcription termination is a molecular defect in MELAS.

UI MeSH Term Description Entries
D009132 Muscles Contractile tissue that produces movement in animals. Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D009154 Mutation Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations. Mutations
D001808 Blood Vessels Any of the tubular vessels conveying the blood (arteries, arterioles, capillaries, venules, and veins). Blood Vessel,Vessel, Blood,Vessels, Blood
D004272 DNA, Mitochondrial Double-stranded DNA of MITOCHONDRIA. In eukaryotes, the mitochondrial GENOME is circular and codes for ribosomal RNAs, transfer RNAs, and about 10 proteins. Mitochondrial DNA,mtDNA
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000077278 RNA, Mitochondrial RNA molecules encoded by the MITOCHONDRIAL GENOME. Mitochondrial RNA,mtRNA
D012313 RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed) RNA, Non-Polyadenylated,Ribonucleic Acid,Gene Products, RNA,Non-Polyadenylated RNA,Acid, Ribonucleic,Non Polyadenylated RNA,RNA Gene Products,RNA, Non Polyadenylated
D012333 RNA, Messenger RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
D017241 MELAS Syndrome A mitochondrial disorder characterized by focal or generalized seizures, episodes of transient or persistent neurologic dysfunction resembling strokes, and ragged-red fibers on muscle biopsy. Affected individuals tend to be normal at birth through early childhood, then experience growth failure, episodic vomiting, and recurrent cerebral insults resulting in visual loss and hemiparesis. The cortical lesions tend to occur in the parietal and occipital lobes and are not associated with vascular occlusion. VASCULAR HEADACHE is frequently associated and the disorder tends to be familial. (From Joynt, Clinical Neurology, 1992, Ch56, p117) Mitochondrial Myopathy, Lactic Acidosis, Stroke-Like Episode,MELAS,Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes,Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, And Stroke-Like Episodes,Myopathy, Mitochondrial-Encephalopathy-Lactic Acidosis-Stroke,Syndrome, MELAS
D017403 In Situ Hybridization A technique that localizes specific nucleic acid sequences within intact chromosomes, eukaryotic cells, or bacterial cells through the use of specific nucleic acid-labeled probes. Hybridization in Situ,Hybridization, In Situ,Hybridizations, In Situ,In Situ Hybridizations

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