1/43. A novel heteroplasmic point mutation in the mitochondrial tRNA(Lys) gene in a sporadic case of mitochondrial encephalomyopathy: de novo mutation and no transmission to the offspring.We have identified a new mutation in the tRNA(Lys) gene of mtDNA, in a 49-year-old patient with mitochondrial encephalomyopathy. The mutation is a heteroplasmic G-->A transition at position 8328, which affects the anticodon stem loop at a conserved site. The mutation was neither found in 100 controls nor in the maternal relatives of the patient. The level of mutated mtDNA was 57% in muscle, 13% in fibroblasts, and 10% in lymphocytes. Histochemistry of muscle tissue revealed cytochrome c oxidase-deficient fibers with abnormal accumulation of mitochondria. biochemistry of muscle mitochondria showed slight cytochrome c oxidase deficiency. The mean ratio of mutant mtDNA to normal mtDNA in cytochrome c oxidase-positive muscle fibers was 59%, whereas a mean ratio of 95% was found in cytochrome c oxidase-negative fibers. The difference between cytochrome c oxidase-positive and cytochrome c oxidase-negative fibers was highly significant (P < 0.001). The mutation was not found in muscle or lymphocytes of the mother and daughter of the proband. This is the first report of a de novo point mutation in the tRNA(Lys) gene in an individual expressing disease and the first report of lack of transmission of the mutation to the offspring of a patient expressing a mitochondrial encephalomyopathy caused by a point mutation in mtDNA.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
2/43. An mtDNA mutation in the initiation codon of the cytochrome C oxidase subunit II gene results in lower levels of the protein and a mitochondrial encephalomyopathy.A novel heteroplasmic 7587T-->C mutation in the mitochondrial genome which changes the initiation codon of the gene encoding cytochrome c oxidase subunit II (COX II), was found in a family with mitochondrial disease. This T-->C transition is predicted to change the initiating methionine to threonine. The mutation load was present at 67% in muscle from the index case and at 91% in muscle from the patient's clinically affected son. Muscle biopsy samples revealed isolated COX deficiency and mitochondrial proliferation. Single-muscle-fiber analysis revealed that the 7587C copy was at much higher load in COX-negative fibers than in COX-positive fibers. After microphotometric enzyme analysis, the mutation was shown to cause a decrease in COX activity when the mutant load was >55%-65%. In fibroblasts from one family member, which contained >95% mutated mtDNA, there was no detectable synthesis or any steady-state level of COX II. This new mutation constitutes a new mechanism by which mtDNA mutations can cause disease-defective initiation of translation.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
3/43. Necrotizing encephalopathy and macrocephaly with mitochondrial complex I deficiency.A neonate presented in the first weeks after birth with vomiting. He was unresponsive, with hypotonia, macrocephaly, and lactic acidosis. The cranial computed tomographic scan revealed a hypodense brain, with increased brain volume and extensive cerebral edema. He died at 6 weeks of age; postmortem examination revealed necrotizing encephalopathy with marked brain edema, spongiosis, thalamic necrosis, and basal ganglia calcifications. Enzyme studies of the mitochondrial respiratory chain revealed complex I deficiency in both muscle and liver.- - - - - - - - - - ranking = 5keywords = deficiency (Clic here for more details about this article) |
4/43. Muscle carnitine acetyltransferase and carnitine deficiency in a case of mitochondrial encephalomyopathy.Profound decrease of the carnitine acetyltransferase activity (0.08 U/g wet weight; 1.67% of control) and carnitine deficiency (total carnitine was 230 nmol/g wet weight in the patient vs 2730 in the controls) was detected in the skeletal muscle of a female paediatric patient. She died of her illness, which included cerebellar symptoms and slight muscle spasticity affecting mainly the lower extremities, at 1 year of age. Histological examination of the autopsy specimens revealed a selective Purkinje cell degeneration in the cerebellum: the cells had abnormal position, were shrunken and decreased in number, and displayed abnormal dendritic trees and fragmented, disorganized axons. Electron microscopy revealed mitochondrial abnormalities in skeletal and cardiac muscle and also in the purkinje cells. Deletions of the mitochondrial dna were detected in the muscle in heteroplasmic form (up to 7%). Mainly the ND4-ND4L region was affected, as evidenced by the PCR; however, other regions of the mitochondrial genome also showed deletions of varying size and extent, suggesting multiple deletions of the mitochondrial dna.- - - - - - - - - - ranking = 5keywords = deficiency (Clic here for more details about this article) |
5/43. Cerebral white matter disease in children may be caused by mitochondrial respiratory chain deficiency.Several mitochondrial diseases are known to occasionally involve the cerebral white matter, namely Leigh syndrome, kearns-sayre syndrome, and melas syndrome, but in these cases the major finding is alteration in the basal ganglia and brainstem. Here we report on severe diffuse white matter involvement and respiratory chain enzyme deficiency or mitochondrial dna rearrangement in 5 unrelated families. It is interesting that white matter lesions were the only abnormal neuroradiologic feature in 3 of the 5 families, and multiple small cyst-like white matter lesions were found in 2 of 5 probands. Respiratory chain deficiency should be considered in the diagnosis of severe white matter involvement in childhood.- - - - - - - - - - ranking = 6keywords = deficiency (Clic here for more details about this article) |
6/43. A new mtDNA mutation associated with a progressive encephalopathy and cytochrome c oxidase deficiency.The authors describe a novel pathogenic G5540A transition in the mitochondrial transfer rna (tRNA)Trp gene of a sporadic encephalomyopathy characterized by spinocerebellar ataxia. Clinical features also included neurosensorial deafness, peripheral neuropathy, and dementia. biochemistry revealed a severe reduction of cytochrome c oxidase (COX) activity. Single-fiber PCR demonstrated higher levels of mutant genomes in COX-negative ragged red fibers than in normal fibers. These findings confirm that COX is more susceptible than other respiratory chain complexes to mutations in the mitochondrial tRNATrp gene.- - - - - - - - - - ranking = 4keywords = deficiency (Clic here for more details about this article) |
7/43. Neuropathological and histochemical changes in a multiple mitochondrial dna deletion disorder.The identification of cytochrome c oxidase (COX)-deficient/succinate dehydrogenase (SDH)- positive cells using sequential histochemistry has proved important in the identification of cells with high mitochondrial dna (mtDNA) mutant load. We demonstrate large numbers of COX-deficient/SDH-positive neurons in a mosaic pattern throughout the CNS of a patient with a multiple mtDNA deletion disorder. This patient had prominent central and peripheral nervous system involvement with marked cerebellar ataxia, a parkinsonian extra-pyramidal movement disorder, external ophthalmoplegia, dysphagia, and a severe peripheral neuropathy. There was degeneration of myelin tracts in the cerebellum and dorsal spinal columns, diffuse astrocytosis, and selective neuronal degeneration particularly in the midbrain and cerebral microvacuolation. The proportional distribution of the COX-deficient neurons did not always correlate directly with the degree of neuropathological damage with regions of high neuronal loss having relatively low proportions of these cells. Other clinically affected CNS regions have high levels of COX-deficient neurons without significant cell loss. The role of these COX-deficient neurons in causing neuronal degeneration and clinical symptoms is discussed.- - - - - - - - - - ranking = 1.029909725856keywords = dehydrogenase (Clic here for more details about this article) |
8/43. Quinone-responsive multiple respiratory-chain dysfunction due to widespread coenzyme Q10 deficiency.BACKGROUND: The respiratory-chain deficiencies are a broad group of largely untreatable diseases. Among them, coenzyme Q10 (ubiquinone) deficiency constitutes a subclass that deserves early and accurate diagnosis. methods: We assessed respiratory-chain function in two siblings with severe encephalomyopathy and renal failure. We used high-performance liquid chromatography analyses, combined with radiolabelling experiments, to quantify cellular coenzyme Q10 content. Clinical follow-up and detailed biochemical investigations of respiratory chain activity were carried out over the 3 years of oral quinone administration. FINDINGS: Deficiency of coenzyme Q10-dependent respiratory-chain activities was identified in muscle biopsy, circulating lymphocytes, and cultured skin fibroblasts. Undetectable coenzyme Q10 and results of radiolabelling experiments in cultured fibroblasts supported the diagnosis of widespread coenzyme Q10 deficiency. Stimulation of respiration and fibroblast enzyme activities by exogenous quinones in vitro prompted us to treat the patients with oral ubidecarenone (5 mg/kg daily), which resulted in a substantial improvement of their condition over 3 years of therapy. INTERPRETATION: Particular attention should be paid to multiple quinone-responsive respiratory-chain enzyme deficiency because this rare disorder can be successfully treated by oral ubidecarenone.- - - - - - - - - - ranking = 598.23439829904keywords = coenzyme, deficiency (Clic here for more details about this article) |
9/43. Mitochondrial encephalomyopathy and complex III deficiency associated with a stop-codon mutation in the cytochrome b gene.We have reinvestigated a young woman, originally reported by us in 1983, who presented with exercise intolerance and lactic acidosis associated with severe deficiency of complex III and who responded to therapy with menadione and ascorbate. Gradually, she developed symptoms of a mitochondrial encephalomyopathy. Immunocytochemistry of serial sections of muscle showed a mosaic of fibers that reacted poorly with antibodies to subunits of complex III but reacted normally with antibodies to subunits of complexes I, II, or IV, suggesting a mutation of mtDNA. These findings demonstrate the diagnostic value of immunocytochemistry in identifying specific respiratory-chain deficiencies and, potentially, distinguishing between nuclear- or mtDNA-encoded defects. sequence analysis revealed a stop-codon mutation (G15242A) in the mtDNA-encoded cytochrome b gene, resulting in loss of the last 215 amino acids of cytochrome b. PCR-RFLP analysis indicated that the G15242A mutation was heteroplasmic and was present in a high percentage (87%) of affected tissue (skeletal muscle) and a low percentage (0.7%) of unaffected tissue (blood) but was not detected in controls. Analysis of microdissected muscle fibers showed a significant correlation between the immunoreactivity toward the Rieske protein of complex III and the percentage of mutant mtDNA: immunopositive fibers had a median value of 33% of the G15242A mutation, whereas immunonegative, ragged-red fibers had a median value of 89%, indicating that the stop-codon mutation was pathogenic in this patient. The G15242A mutation was also present in several other tissues, including hair roots, indicating that it must have arisen either very early in embryogenesis, before separation of the primary germ layers, or in the maternal germ line. The findings in this patient are contrasted with other recently described patients who have mutations in the cytochrome b gene.- - - - - - - - - - ranking = 5keywords = deficiency (Clic here for more details about this article) |
10/43. Mitochondrial dna depletion associated with partial complex II and IV deficiencies and 3-methylglutaconic aciduria.We report a patient with mitochondrial dna depletion, partial complex II and IV deficiencies, and 3-methylglutaconic aciduria. Complex II deficiency has not been previously observed in mitochondrial dna depletion syndromes. The observation of 3-methylglutaconic and 3-methylglutaric acidurias may be a useful indicator of a defect in respiratory chain function caused by mitochondrial dna depletion.- - - - - - - - - - ranking = 1keywords = deficiency (Clic here for more details about this article) |
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