Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rapid progress has been made in the identification of mitochondrial DNA mutations which are typically associated with diseases of the nervous system and muscle. The well established mitochondrial disorders are maternally inherited and males and females are equally affected. An exception is Leber's hereditary optic atrophy (LHON) which is observed much more frequently in males than in females. There are three common point mutations in LHON which can be homoplasmic or heteroplasmic. In mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) most mutations are single base changes and lie within the tRNA-Leu gene. Point mutations in myoclonic epilepsy with ragged red fibres (MERRF) usually occur within the tRNA-Lys gene but mutations of the tRNA-Leu gene are also observed. MELAS and MERRF mutations are heteroplasmic and there is considerable clinical overlap between these diseases. Point mutations within the ATPase6 gene result in either neuropathy, ataxia and retinitis pigmentosa (NARP) or in Leigh's syndrome. The latter occurs if the mutation is present in the majority of mitochondria (extreme heteroplasmy). Finally, mitochondrial DNA deletions are the cause underlying Kearns-Sayre syndrome (KSS). Apart from the well-established mitochondrial diseases, there is increasing evidence that mitochondrial mutations may also play a role in the neurodegenerative disorders Parkinson, Alzheimer and Huntington disease. The complex I defect found in Parkinson disease is especially interesting in this respect. However, no causative mitochondrial mutation has as yet been established in any of these three common disorders.
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PMID:Recent developments in the molecular genetics of mitochondrial disorders. 951 82

Point and deletion mutations and a general depletion of mammalian mitochondrial DNA (mtDNA) give rise to a wide variety of medical syndromes that are refractory to treatment, possibly including aging itself. While gene therapy directed at correcting such deficits in the mitochondrial genome may offer some therapeutic benefits, there are inherent problems associated with a direct approach. These problems are primarily due to the high mitochondrial genome copy number in each cell and the mitochondrial genome being "protected" inside the double-membrane mitochondrial organelle. In an alternative approach there is evidence that genes normally present in the mitochondrial genome can be incorporated into the nuclear genome. To extend such studies, we modified the Chinese Hamster Ovary (CHO) mtDNA-located ATPase6 gene (possessing a mutation which confers oligomycin resistance- oli(r)) by altering the mtDNA code to the universal code (U-code) to permit the correct translation of its mRNA in the cytoplasm. The U-code construct was inserted into the nuclear genome (nucDNA) of a wild type CHO cell. The expressed transgene products enabled the transformed CHO cell lines to grow in up to 1000 ng mL(-1) oligomycin, while untransformed sensitive CHO cells were eliminated in 1 ng mL(-1) oligomycin. This approach, termed allotopic expression, provides a model that may make possible the transfer of all 13 mtDNA mammalian protein-encoding genes to the nucDNA, for treatments of mtDNA disorders. The CHO mtATPase6 protein is 85% identical to both the mouse and human mtATPase6 protein; these proteins are highly conserved in the region of the oligomycin resistance mutation. They are also well conserved in the regions of the oligomycin resistance mutation of the mouse, and in the region of a mutation found in Leigh's syndrome (T8993G), also called NARP (neurogenic weakness, ataxia, retinitis pigmentosum). It is likely that the CHO oli(r) mtATPase6 Ucode construct could impart oligomycin-resistance in human and mouse cells, as well as function in place of the mutant ATPase subunit in a NARP cell line. Preliminary experiments on human cybrids homoplasmic for the NARP mutation (kindly supplied by D.C. Wallace), transformed with our construct, display an increased oligomycin resistance that supports these suppositions.
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PMID:Stable transformation of CHO Cells and human NARP cybrids confers oligomycin resistance (oli(r)) following transfer of a mitochondrial DNA-encoded oli(r) ATPase6 gene to the nuclear genome: a model system for mtDNA gene therapy. 1579 71