title: Deficiency of complex II of the mitochondrial respiratory chain in late-onset optic atrophy and ataxia.
abstract: Defects of the mitochondrial respiratory chain are increasingly being recognized as an important cause of neurological disease in humans. In many of these patients, the biochemical defect results from an abnormality of the mitochondrial genome. Respiratory chain defects involving complex II, which is entirely encoded by the nuclear genome, are comparatively rare. We report the clinical and biochemical findings in 2 elderly sisters who presented with late-onset neurodegenerative disease. In both patients, a partial deficiency of complex II (approximately 50% of control values) was shown to be present in mitochondria from muscle and platelets. The enzyme defect was not expressed in cultured skin fibroblasts or immortalized lymphocytes. There was an overexpression of the 70-kd flavoprotein subunit in muscle mitochondria from both patients, although we showed that this subunit is present in normal amounts in mitochondrial membranes. Our studies highlight the diversity of the clinical presentation of respiratory chain disease and that complex II deficiency should enter the differential diagnosis of certain patients with late-onset neurodegenerative disease.
authors.affiliation: Departments of Neurology and Ophthalmology, University of Newcastle upon Tyne, U.K.
authors.forename: R W
authors.initials: RW
authors.lastname: Taylor
authors.forename: M A
authors.initials: MA
authors.lastname: Birch-Machin
authors.forename: J
authors.initials: J
authors.lastname: Schaefer
authors.forename: L
authors.initials: L
authors.lastname: Taylor
authors.forename: R
authors.initials: R
authors.lastname: Shakir
authors.forename: B A
authors.initials: BA
authors.lastname: Ackrell
authors.forename: B
authors.initials: B
authors.lastname: Cochran
authors.forename: L A
authors.initials: LA
authors.lastname: Bindoff
authors.forename: M J
authors.initials: MJ
authors.lastname: Jackson
authors.forename: P
authors.initials: P
authors.lastname: Griffiths
authors.forename: D M
authors.initials: DM
authors.lastname: Turnbull
mesh_terms: D001259:Ataxia / Q000235:genetics / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism; D002478:Cells, Cultured; D004579:Electron Transport; D042963:Electron Transport Complex II; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D005420:Flavoproteins / Q000378:metabolism; D006651:Histocytochemistry; D006801:Humans; D015151:Immunoblotting; D008214:Lymphocytes / Q000201:enzymology; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000172:deficiency*; D009896:Optic Atrophy / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases / Q000172:deficiency*; D010375:Pedigree; D012867:Skin / Q000201:enzymology / Q000473:pathology; D013385:Succinate Dehydrogenase / Q000172:deficiency*
chemical_list: D005420:Flavoproteins; D009097:Multienzyme Complexes; D010088:Oxidoreductases; D042963:Electron Transport Complex II; D013385:Succinate Dehydrogenase