Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although an apparently generalized defect of cytochrome c oxidase (COX) occurs in many patients with subacute necrotizing encephalomyelopathy (Leigh's syndrome), the mode of inheritance in this disorder is not known. We transformed COX-deficient fibroblasts from a child with Leigh's syndrome with simian virus 40 to obtain cells with an infinite life span. These cells were still COX-deficient, grew normally in HAT medium, and were ouabain-sensitive. We fused these cells with a HAT-sensitive, ouabain-resistant variant of HeLa cells (HeLacot) and isolated surviving hybrid clones in ouabain-containing HAT medium. Prolonged cultivation of the hybrids was accompanied by preferential loss of HeLacot mitochondrial DNA (mtDNA), as determined by mtDNA restriction patterns of parental and hybrid cell DNA with the restriction endonuclease HaeII. COX activity was normal or higher than normal in hybrids, including the progeny of cell clones that had lost almost all the HeLacot mtDNA. These data demonstrate that COX deficiency in this Leigh's syndrome patient's cells was corrected by a nuclear DNA-encoded factor from the HeLacot parent and ruled out an mtDNA mutation as the basis for COX deficiency. This system can be used to determine whether different generalized mitochondrial disorders are due to mutations of nuclear or mtDNA.
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PMID:Cytochrome c oxidase deficiency in Leigh's syndrome: genetic evidence for a nuclear DNA-encoded mutation. 254 Apr 52

The restriction endonuclease SmaI has been used for the diagnosis of neurogenic muscle weakness, ataxia and retinitis pigmentosa disease or Leigh's disease, caused by the Mt8993T-->G mutation which results in a Leu156Arg replacement that blocks proton translocation activity of subunit a of F(0)F(1)-ATPase. Our ultimate goal is to apply SmaI to gene therapy for this disease, because the mutant mitochondrial DNA (mtDNA) coexists with the wild-type mtDNA (heteroplasmy), and because only the mutant mtDNA, but not the wild-type mtDNA, is selectively restricted by the enzyme. For this purpose, we transiently expressed the SmaI gene fused to a mitochondrial targeting sequence in cybrids carrying the mutant mtDNA. Here, we demonstrate that mitochondria targeted by the SmaI enzyme showed specific elimination of the mutant mtDNA. This elimination was followed with repopulation by the wild-type mtDNA, resulting in restoration of both the normal intracellular ATP level and normal mitochondrial membrane potential. Furthermore, in vivo electroporation of the plasmids expressing mitochondrion-targeted EcoRI induced a decrease in cytochrome c oxidase activity in hamster skeletal muscles while causing no degenerative changes in nuclei. Delivery of restriction enzymes into mitochondria is a novel strategy for gene therapy of a special form of mitochondrial diseases.
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PMID:Gene therapy for mitochondrial disease by delivering restriction endonuclease SmaI into mitochondria. 1237 91

The mitochondrial tRNA(Leu(UUR)) gene (MTTL) is a hot spot for pathogenic mutations that are associated with mitochondrial diseases with various clinical features. Among these mutations, the A3243G mutation was associated with various types of mitochondrial multisystem disorders, such as MIDD, MELAS, MERRF, PEO, hypertrophic cardiomyopathy, and a subtype of Leigh syndrome. We screened 128 Tunisian patients for the A3243G mutation in the mitochondrial tRNA(Leu(UUR)) gene. This screening was carried out using PCR-RFLP with the restriction endonuclease ApaI. None of the 128 patients or the 100 controls tested were found to carry the mitochondrial A3243G mutation in the tRNA(Leu(UUR)) gene in homoplasmic or heteroplasmic form. After direct sequencing of the entire mitochondrial tRNA(Leu(UUR)) gene and a part of the mitochondrial NADH dehydrogenase 1, we found neither mutations nor polymorphisms in the MTTL1 gene in the tested patients and controls, and we confirmed the absence of the A3243G mutation in this gene. We also found a T3396C transition in the ND1 gene in one family with NSHL which was absent in the other patients and in 100 controls. Neither polymorphisms nor other mutations were found in the mitochondrial tRNA(Leu(UUR)) gene in the tested patients.
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PMID:Mutational analysis of the mitochondrial tRNALeu(UUR) gene in Tunisian patients with mitochondrial diseases. 1733 24

Leigh syndrome is a genetically heterogeneous, neurodegenerative disorder that predominantly affects children and leads to death within months or years. Mutations causing this disease have been found in both mitochondrial and nuclear DNA. The present report describes a Tunisian family with a maternally inherited Leigh syndrome harboring the mitochondrial T8993G mutation in the ATPase 6 gene. Polymerase chain reaction-restriction fragment length polymorphism analysis with the MspI restriction endonuclease, quantified with a digital image analyzer and gel documentation system, showed that the T8993G mutation was present with a high percentage in the blood of the three patients tested. This mutation was also detected in the asymptomatic mothers of these three patients (90, 96, and 60%). Two novel mitochondrial mutations were identified in the mitochondrial ATP6 gene -- T8741G (L72R) and A8795G (H90R) -- and three novel polymorphisms. Altogether, Leigh syndrome presenting the T8993G mutation in the ATPase 6 gene with variable heteroplasmic loads (44-98%) in a single Tunisian family is a novel finding.
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PMID:Maternally inherited Leigh syndrome: T8993G mutation in a Tunisian family. 1943 77