GLUTARIC ACIDEMIA--MOLECULAR, BIOCHEMICAL, AND CHEMICAL HETEROGENEITY

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Glutaric acidemia (GAI) is a human inborn error of lysine and tryptophan oxidation which causes degeneration of the basal ganglia and a progressive movement disorder in childhood. Death usually occurs during the first decade. The condition is due to deficiency of glutaryl-C0A dehydrogenase (GCDH), an FAD- containing mitochondrial enzyme that oxidatively decarboxylates glutaryl-CoA to crotonyl-CoA and CO2. We have been studying this disorder for almost twenty years, being the first to describe the disease and to characterize its organic aciduria, neuropathology, and enzyme defect. We have cloned and expressed cDNA encoding human GCDH and identified several mutations that cause GAI, with the objective of learning how these mutations relate to pathophysiology and clinical heterogeneity, and the catalytic pathways of normal and mutant enzymes. Specific aims for this funding period are to (a) delineate GCDH mutations that cause GAI, (b) correlate these mutations with functional abnormalities in the expressed enzyme to develop a detailed structure-function map of human GCDH, and examine the relations between phenotype and GCDH genotype to develop testable hypotheses about factors contributing to clinical heterogeneity. In this context, specific aim (c) examines the hypothesis t hat differential processing of GCDH transcripts with a specific splice site mutation is responsible for clinical heterogeneity in a population in which all patients are homozygous for this mutant allele. Methods to be employed include single strand conformation polymorphism analysis of GCDH exons, expression of mutant GCDH in E coli, spectral and kinetic studies of normal and mutant GCDH, and RT-PCR of fibroblast mRNA in GAI patients.