Isolation of mammalian cell mutants deficient in glucose-6-phosphate dehydrogenase activity: linkage to hypoxanthine phosphoribosyl transferase

Abstract

Mutants of Chinese hamster ovary cells deficient in glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP 1-oxidoreducatse, EC 1.1.1.49) activity were isolated after mutagenesis with ethyl methane sulfonate. The mutants were induced at frequencies of about 10-4 and do not differ in growth properties from wild-type cells. They were isolated by means of a sib selection technique coupled with a histochemical stain of colonies for enzyme activity. The lack of enzyme activity is not due to a dissociable inhibitor, and is recessive in hybrid cells. Multiple mutants that lack hypoxanthine phosphoribosyltransferase activity (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) and adenine phosphoribosyltransferase activity (AMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.7) were isolated by further mutagenesis. By following segregation of wild-type phenotypes from heterozygous multiply marked hybrid cells, it was shown that the genes responsible for glucose-6-phosphate dehydrogenase activity and hypoxanthine phosphoribosyltransferase activity are linked in Chinese hamster cells, in agreement with the location of both on the X chromosome in humans. No linkage to adenosine phosphoribosyltransferase was found. The isolation of mutant cells carrying linked markers should prove useful for studying chromosomal events such as segregation, breakage, recombination, and X-chromosome reactivation.