Molecular Ivestigation of the Electron Transfer Flavoprotein Dehydrogenase Mutation Induced Mitochondrial Dysfunction and Metabolic Defects

Multiple acyl-CoA dehydrogenase deficiency (MADD), glutaric aciduria type II, is an autosomal recessive inherited disorder of fatty acid metabolism. Electron-transfer-flavoprotein dehydrogenase (ETFDH) gene encodes electron-transfer-flavoprotein-ubiquinone oxidoreductase (ETFQO) have been reported to be the major causes of MADD. The ETF/ETF-QO system serves as electron transfer in mitochondrial electron transport chain and links fatty acids oxidation to supply mitochondrial respiratory substrate. The etiology and pathophysiology of ETFDH deficiency induced MADD remains uncertain. In our index family, we found there were two point mutations: c. 92C>T and c.250G>A. The MADD pedigree was identified with myopathy that oil droplet accumulation, abnormal plasma fatty acid compositions, and mitochondrial abnormality. The clinical manifestations were improved followed CoQ10 treatment. We therefore postulate that this MADD pedigree may result from defects of ETF-QO combined with general mitochondrial dysfunction. We proposed that ETFDH mutation induced mitochondrial dysfunction and metabolic defects contributing to MADD pathogenesis. To underlying the pathogenesis of this fatty acid degradation disorder, we plan to set up this project for three years. In the first year, we plan to investigate the genetic and pathological background of this MADD pedigree, and establish the patient-derived lymphoblastoid cell lines for cell-based functional assays. We plan to investigate whether ETHDH mutations induce lipid droplet accumulation in human lymphoblast cells in response to the treatment of fatty acid of various chain lengths. In the second year, we plan to verify whether ETFDH mutation induces the lipid droplet accumulation via mitochondrial dysfunction. We will establish the human myoblast stable cell lines with specific ETFDH mutation to evaluate the effect of fatty acids on mitochondrial dysfunction and lipid droplet accumulation. In the third year, we plan to establish cell-based stressor or drug screening platform for the ETFDH-mutated myoblast cell lines by monitoring lipid droplet accumulation and mitochondrial respiration. We will find out the rescue effects from riboflavin, CoQ10, and pyrroloquinoline quinone treatment, and examine the detrimental effect of heat stress and the inflammatory cytokine on the specific ETFDH- mutated myoblast cell lines. This will help to disclose the Taiwan-specific variation of MADD and the therapeutics for treatment.