DEVELOPMENT OF A NOVEL MOUSE TK(+ -) EMBRYONIC STEM-CELL LINE FOR USEIN MUTAGENICITY STUDIES/

A tk(+/-) mouse embryonic stem (ES) cell I ne, designated 1G2, has bee n created in which one allele of the thymidine kinase (ik) gene was in activated by targeted homologous recombination. This line is an analog of the mouse lymphoma tk(+/-) L5178Y cell line, which is used widely to assess the mutagenicity of chemical agents. Treatment of 1G2 cells with the alkylating agent N-ethyl-N-nitrosourea (ENU) resulted in a do se-related increase in trifluorothymidine-resistant colonies. Mutant f requencies of 152 and 296 per 10(6) cells were determined for 0.1 and 0.3 mg/ml doses of ENU, compared with a spontaneous mutant frequency o f 15 per 10(6) cells. The data indicate that tk(+/-) 1G2 ES cells may be useful for the creation of a transgenic mouse model for assessing i n vivo mutation using an endogenous autosomal gene. (C) 1996 Wiley-Lis s, Inc.