title: Use of selective media for distinguishing variant forms of hypoxanthine phosphoribosyl transferase.
abstract: Growth properties of cultured fibroblasts in selective media were used to characterize the HPRT enzyme of a patient with a new variant of hypoxanthine phosphoribosyl transferase (HPRT) with deficient activity. The clinical phenotype of the patient was typical of the Lesch-Nyhan syndrome. However, cells of the patient were not selected for by growth in either 8-azaguanine or 6-thioguanine. Assay of the activity of the enzyme in erythrocyte lysates revealed values of approximately zero, while in the intact fibroblast assay the level of activity was 1.4% of normal. The heterozygous mother of the patient, unlike heterozygotes for the classic Lesch-Nyhan enzyme, had a level of activity in erythrocyte lysates that was 45% of control. In the presence of selective agents in vitro the cells of the patient retained sufficient HPRT activity to permit a degree of toxicity indistinguishable from that observed in normal cells although the degree of the deficiency was so great that it led to the complete Lesch-Nyhan phenotype. These findings call into question the use of selective agents for the identification of HPRT- cells in the detection of heterozygosity.
mesh_terms: D000328:Adult; D002384:Catalysis; D002455:Cell Division; D002478:Cells, Cultured; D004912:Erythrocytes / Q000201:enzymology; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D007926:Lesch-Nyhan Syndrome / Q000201:enzymology*; D008297:Male; D010641:Phenotype
chemical_list: D007041:Hypoxanthine Phosphoribosyltransferase