title: Lower mutation frequencies are induced by ENU in undifferentiated embryonic cells than in differentiated cells of the mouse in vitro.
abstract: The pluripotent embryonic carcinoma cells of line P19 established from undifferentiated cells of the early mouse embryo and their differentiated progeny, the epithelioid ectoderm-like EPI-7 cells, were investigated for the induction of mutations at the HPRT locus by the alkylating agent N-ethyl-N-nitrosourea (ENU). We showed that the cytotoxic effects of ENU after a 5-h treatment were lower in undifferentiated P19 cells than in differentiated EPI-7 cells. The IC50 values of ENU in the two cell lines amounted to 0.6 mg/ml and 0.09 mg/ml for P19 and EPI-7 cells, respectively. The induction of 6-thioguanine-resistant mutants by ENU (1.0 mg/ml) determined after an expression time of 8 days for both cell lines resulted in similar mutation frequencies. Using expression times of 8 days for P19 and 11.75 days for EPI-7 cells, taking into account the longer generation time of differentiated EPI-7 cells (13.7 +/- 3.6 h) in comparison to undifferentiated P19 cells (9.3 +/- 0.9 h), ENU induced significantly higher mutant frequencies in EPI-7 cells (4865 mutants/10(6) cells) than in P19 cells (282 mutants/10(6) cells). Our results and data from the literature on UV irradiation-induced repair support the idea that the induction of lower mutation frequencies in embryonic cells may correlate with different proliferation capacities, cell cycle parameters and/or different mechanisms of DNA repair in embryonic stem cells and differentiated cells, respectively.
authors.affiliation: Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Sehlmeyer
authors.forename: A M
authors.initials: AM
authors.lastname: Wobus
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D004351:Drug Resistance; D004622:Embryo, Mammalian; D005038:Ethylnitrosourea / Q000633:toxicity*; D051379:Mice; D009152:Mutagenicity Tests; D009154:Mutation; D013866:Thioguanine / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D013866:Thioguanine; D005038:Ethylnitrosourea