GENETIC COMPLEMENTATION OF PROPIONYL-COA CARBOXYLASE DEFICIENCY IN CULTURED HUMAN FIBROBLASTS

  • 1 January 1977
    • journal article
    • research article
    • Vol. 29  (4) , 378-388
Abstract
Propionyl-CoA carboxylase (PCC) deficiency is an inherited metabolic disorder showing considerable variability of expression. The possibility that there is a genetic basis for the clinical heterogeneity in this disorder by examining complementation in Sendai virus mediated heterokaryons of human mutant fibroblast strains was investigated. Restoration of PCC activity was monitored in individual multinucleate cells in situ using a radioautographic procedure which detects the incorporation of 14C-propionate into trichloracetic acid precipitable material. Each mutant strain incorporated negligible amounts of radioactivity compared to control strains. Activity was not restored when different mutants were mixed without virus or when homokaryons were produced by self-fusion. Seven mutant strains were fused in all pairwise combinations and examined for increased 14C-propionate incorporation in heterokaryons. Two main complementation groups were revealed. One group was composed of 3 mutants. The other was a complex group composed of 4 mutants in which intragroup complementation was demonstrated. Two mutants showing excellent complementation by radioautography were examined for complementation by the direct assay of PCC activity. The enzyme activity of virus-treated preparations with 23% multinucleate cells was 183 Units (pmol/min per mg protein) compared to 16 units for the untreated mixture (normal range 450-850 units). PCC deficiency may result from mutations of heterogeneous origin, although the classification of mutants into complementation groups did not correlate with patterns of clinical heterogeneity.