Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0016719 (Friedreich's ataxia)
 2,098 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A potential pivotal role for mitochondrial dysfunction in neurodegenerative diseases is gaining increasing acceptance. Mitochondrial dysfunction leads to a number of deleterious consequences including impaired calcium buffering, generation of free radicals, activation of the mitochondrial permeability transition and secondary excitotoxicity. Neurodegenerative diseases of widely disparate genetic etiologies may share mitochondrial dysfunction as a final common pathway. Recent studies using cybrid cell lines suggest that sporadic Alzheimer's disease is associated with a deficiency of cytochrome oxidase. Friedreich's ataxia is caused by an expanded GAA repeat resulting in dysfunction of frataxin, a nuclear encoded mitochondrial protein involved in mitochondrial iron transport. This results in increased mitochondrial iron and oxidative damage. Familial amyotrophic lateral sclerosis is associated with point mutations in superoxide dismutase, which may lead to increased generation of free radicals and thereby contribute to mitochondrial dysfunction. Huntington's disease (HD) is caused by an expanded CAG repeat in an unknown protein termed huntingtin. The means by which this leads to energy impairment is unclear, however studies in both HD patients and a transgenic mouse model show evidence of bioenergetic defects. Mitochondrial dysfunction leads to oxidative damage which is well documented in several neurodegenerative diseases. Therapeutic approaches include methods to buffer intracellular ATP and to scavenge free radicals.
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PMID:Mitochondrial dysfunction in neurodegenerative diseases. 971 10

Mutations of mitochondrial DNA (mtDNA) are associated with a wide spectrum of disorders encompassing the myopathies, encephalopathies and cardiomyopathies, in addition to organ specific presentations such as diabetes mellitus and deafness. The pathogenesis of mtDNA mutations is not fully understood although it is assumed that their final common pathway involves impaired oxidative phosphorylation. The identification of a specific respiratory chain defect (complex I deficiency) in Parkinson's disease (PD) 10 years ago focused attention on the aetiological and pathogenetic roles that mitochondria may play in neurodegenerative diseases. There is evidence now emerging that mtDNA abnormalities may determine the complex I defect in a proportion of PD patients and it may prove possible to use biochemical analysis of platelet and cybrid complex I function to identify those that lie within this group. Respiratory chain defects of a different pattern have been identified in Huntington's disease (HD) (complex II/III deficiency) and Friedreich's ataxia (FA) complex I-III deficiency). In both these disorders, the mitochondrial abnormality is secondary to the primary nuclear mutation:CAG repeat in the huntingtin gene in HD, and GAA repeat in the frataxin gene in FA. Nevertheless, it appears that the mitochondrion may be the target of the biochemical defects that are the consequence of these mutations. There is a close and reciprocal relationship between respiratory chain dysfunction and free radical generation, and there is evidence for oxidative stress and damage in PD, HD and FA, which together with the mitochondrial defect may result in cell damage. Impaired oxidative phosphorylation and free radical generation may independently adversely affect the maintenance of mitochondrial transmembrane potential (Deltapsim). A fall in Deltapsim is an early event (preceding nuclear fragmentation) in the apoptotic pathway. It is possible therefore that mitochondrial dysfunction in the neurodegenerative disorders may result in a fall in the apoptotic threshold of neurones which, in some, may be sufficient to induce cell death whilst, in others, additional factors may be required. In any event, mitochondria present an important target for future strategies for 'neuroprotection' to prevent or retard neurodegeneration.
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PMID:Mitochondrial dysfunction in neurodegenerative disorders. 971 16

In mammalian cells, mitochondria provide energy from aerobic metabolism. They play an important regulatory role in apoptosis, produce and detoxify free radicals, and serve as a cellular calcium buffer. Neurodegenerative disorders involving mitochondria can be divided into those caused by oxidative phosphorylation (OXPHOS) abnormalities either due to mitochondrial DNA (mtDNA) abnormalities, e.g., chronic external ophthalmoplegia, or due to nuclear mutations of OXPHOS proteins, e.g., complex I and II associated with Leigh syndrome. There are diseases caused by nuclear genes encoding non-OXPHOS mitochondrial proteins, such as frataxin in Friedreich ataxia (which is likely to play an important role in mitochondrial-cytosolic iron cycling), paraplegin (possibly a mitochondrial ATP-dependent zinc metalloprotease of the AAA-ATPases in hereditary spastic paraparesis), and possibly Wilson disease protein (an abnormal copper transporting ATP-dependent P-type ATPase associated with Wilson disease). Huntingon disease is an example of diseases with OXPHOS defects associated with mutations of nuclear genes encoding non-mitochondrial proteins such as huntingtin. There are also disorders with evidence of mitochondrial involvement that cannot as yet be assigned. These include Parkinson disease (where a complex I defect is described and free radicals are generated from dopamine metabolism), amyotrophic lateral sclerosis, and Alzheimer disease, where there is evidence to suggest mitochondrial involvement perhaps secondary to other abnormalities.
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PMID:Mitochondria and degenerative disorders. 1157 22

Ataxia with ocular motor apraxia type 1 (AOA1) is an autosomal recessive cerebellar ataxia (ARCA) associated with oculomotor apraxia, hypoalbuminaemia and hypercholesterolaemia. The gene APTX, which encodes aprataxin, has been identified recently. We studied a large series of 158 families with non-Friedreich progressive ARCA. We identified 14 patients (nine families) with five different missense or truncating mutations in the aprataxin gene (W279X, A198V, D267G, W279R, IVS5+1), four of which were new. We determined the relative frequency of AOA1 which is 5%. Mutation carriers underwent detailed neurological, neuropsychological, electrophysiological, oculographic and biological examinations, as well as brain imaging. The mean age at onset was 6.8 +/- 4.8 years (range 2-18 years). Cerebellar ataxia with cerebellar atrophy on MRI and severe axonal sensorimotor neuropathy were present in all patients. In contrast, oculomotor apraxia (86%), hypoalbuminaemia (83%) and hypercholesterolaemia (75%) were variable. Choreic movements were frequent at onset (79%), but disappeared in the course of the disease in most cases. However, a remarkably severe and persistent choreic phenotype was associated with one of the mutations (A198V). Cognitive impairment was always present. Ocular saccade initiation was normal, but their duration was increased by the succession of multiple hypometric saccades that could clinically be confused with 'slow saccades'. We emphasize the phenotypic variability over the course of the disease. Cerebellar ataxia and/or chorea predominate at onset, but later on they are often partially masked by severe neuropathy, which is the most typical symptom in young adults. The presence of chorea, sensorimotor neuropathy, oculomotor anomalies, biological abnormalities, cerebellar atrophy on MRI and absence of the Babinski sign can help to distinguish AOA1 from Friedreich's ataxia on a clinical basis. The frequency of chorea at onset suggests that this diagnosis should also be considered in children with chorea who do not carry the IT15 mutation responsible for Huntington's disease.
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PMID:Cerebellar ataxia with oculomotor apraxia type 1: clinical and genetic studies. 1450 70