GENETIC COMPLEMENTATION ANALYSIS OF 3-HYDROXY-3-METHYLGLUTARYL-COENZYME-A LYASE DEFICIENCY IN CULTURED FIBROBLASTS

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 36  (4) , 791-801
Abstract
3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase deficiency is an inherited metabolic disorder of leucine catabolism showing variability in clinical expression. The possibility of a biochemical and genetic basis for this heterogeneity was examined by measuring the residual enzyme activities in fibroblasts cultured from 7 patients. The mean activity of HMG-CoA lyase was 1.1% .+-. 0.3% of normal with no significant differences between the patients. Genetic complementation was studied in heterokaryons obtained by fusion with polyethylene glycol using the incorporation of 1-[14C]isovaleric acid into trichloroacetic acid precipitable material to determine the activity of the leucine catabolic pathway. Unfused cells from the patients with a deficiency of HMG-CoA lyase had incorporations of less that 5% of normal. Unfused cells from patients with isovaleric acidemia or a deficiency of 3-methylcrotonyl-CoA carboxylase also had incorporations of less than 5% of normal, and when fused with cells of patients with a deficiency of HMG-CoA lyase, gave positive complementation with an incorporation of 30% normal. None of the fusions between the 7 different lines deficient in HMG-CoA lyase resulted in increased incorporation. No evidence was obtained for biochemical or genetic heterogeneity in fibroblasts of these 7 patients with a deficiency of HMG-CoA lyase that would account for their different clinical presentations.