Deficiency of complex III of the mitochondrial respiratory chain in a patient with facioscapulohumeral disease.
Facioscapulohumeral disease (FSHD), an inherited neuromuscular disorder, is characterized by progressive wasting of specific muscle groups, particularly the proximal musculature of the upper limbs; the primary defect in this disorder is unknown. We studied a patient with FSHD to determine whether the mitochondrial respiratory chain was functionally abnormal. Muscle biopsy revealed fiber atrophy with patchy staining for oxidative enzymes. Electron microscopy of a liver section showed many enlarged mitochondria with paracrystalline inclusions. Decreased oxidation of the respiratory substrates-alanine and succinate-in skin fibroblasts suggested a deficiency of complex III of the electron-transport chain; cytochrome c oxidase activity (complex IV) was in the normal range. Biochemical analysis of liver supported the fibroblast data, since succinate oxidase activity (electron-transport activity through complexes II-IV) was reduced, whereas complex IV activity was normal. Furthermore, analysis of the cytochrome spectrum in liver revealed typical peaks for cytochromes cc1 and aa3, whereas cytochrome b (a component of complex III) was undetectable. Southern blot analysis of fibroblast mtDNA revealed no major deletions or rearrangements. Our study provides the first documentation of a specific enzyme-complex deficiency associated with FSHD.[1]References
- Deficiency of complex III of the mitochondrial respiratory chain in a patient with facioscapulohumeral disease. Slipetz, D.M., Aprille, J.R., Goodyer, P.R., Rozen, R. Am. J. Hum. Genet. (1991) [Pubmed]
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