OXIDATIVE-METABOLISM IN RETT-SYNDROME .2. BIOCHEMICAL AND MOLECULAR STUDIES

In an attempt to identify a possible defect of mitochondrial metabolis m in Rett syndrome we studied 9 girls with typical Rett syndrome using a clinical protocol designed to identify disorders of oxidative metab olism. One girl, (RO) had marked lactic acidemia. Biochemical studies on samples from these patients included leukocyte pyruvate carboxylase assay, serum biotinidase and skin fibroblast pyruvate production, pyr uvate dehydrogenase, citrate synthetase and 2-oxoglutarate dehydrogena se assay. Muscle electron transport activities were studied on samples from 4 typical Rett patients including RO. Mitochondrial DNA (mtDNA) mutational analysis for the np3243 MELAS mutation, the np8993 NARP mut ation, the np8344 MERFF mutation and the 4977 kb common deletion found in Kearns-Sayre syndrome and aged tissues were tested for in 1 of the muscle samples and 2 blood samples from typical Rett patients. Wester n blotting of electron transport complex III was performed on mitochon drial samples obtained from autopsy brain tissue in 2 Rett patients an d compared to pediatric control brain samples. No abnormalities were f ound in blood biotinidase or pyruvate carboxylase. Western blotting of 2 Rett brain mitochondrial samples for complex III appear normal. Pyr uvate consumption in medium from 8 Rett fibroblast Lines grown with an d without dichloroacetate (DCA) showed a normal fall in pyruvate sugge sting normal pyruvate dehydrogenase activity in these cells, however t he fibroblasts from patient RO had a high pyruvate production in cultu re. Pyruvate dehydrogenase, 2-oxo-glutarate dehydrogenase and citrate synthetase activities in 8 Rett fibroblast lines were normal. Muscle m itochondrial activities in 4 Rett patients were normal for citrate syn thetase and electron transport complexes I, II/III, Ill and IV (cytoch rome oxidase), however, muscle cytochrome oxidase activity fell on rep etitive assay in one patient (RO) raising a question about excessive l ability of the complex in this patient to repeated freeze thawing. Mus cle histochemical staining for cytochrome oxidase in patient RO was no rmal. All mtDNA studies were negative.