GLUTARIC ACIDEMIA--MOLECULAR, BIOCHEMICAL, AND CHEMICAL HETEROGENEITY

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Glutaric acidemia type 1 (GA1) is a human inborn error of lysine and tryptophan oxidation which causes a progressive movement disorder in childhood due to acute degeneration of the basal ganglia, usually during or following an intercurrent infection. Metabolic signs such as acidosis and hypoglycemia are rare, and death usually occurs during the first decade of life. The condition is due to deficiency of glutaryl-CoA dehydrogenase, an FAD-containing mitochondrial enzyme which oxidatively decarboxylates glutaryl-CoA to CO2. We have been studying this disorder for more than twenty-five years, being the first to describe the disease and to characterize its organic aciduria, neuropathology, and enzyme defect. We also cloned and expressed human cDNA encoding GCD, and have identified most of the many mutations that are known to be disease-causing. Specific aims for this funding period are to continue mutation analysis in GA1 patients, and to determine the reasons for the occasional discrepancy between the activity of GCD mutations when expressed in E coli and GCD activity in fibroblasts of patients who are compound heterozygotes for two different mutations. This will be done by co-expressing the different GCD mutations in E coli, and determine if intragenic complementation occurs between certain mutant proteins. Also, having now used gene knockout technology to identify sites of GCD activity in the brain, we will develop a murine knockout model of GA1 to examine the effect of GCD deficiency on brain development and structure. Like GA1, D-2-hydroxyglutaric acidemia is an inherited neurologic disease with few metabolic consequences. It is inherited as an autosomal recessive trait and in its severe form, which is consistent within families, causes neonatal onset of seizures, hypotonia, blindness and developmental delay. The cause of D-2-hydroxyglutaric acid accumulation is unknown, as is its usual source and disposition. The cause of D-2-hydroxyglutaric acid accumulation is known, as its usual source and disposition. The accumulation of D-2-hydroxyglutaric acid or a thiol ester, and biochemical and molecular biology approaches are proposed to examine the hypothesis that the disorder is due to inherited deficiency of this dehydrogenase.