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Further characterization and validation of gpt delta transgenic mice for quantifying somatic mutations in vivo
Author(s) -
Swiger Roy R.,
Cosentino Lidia,
Masumura KenIchi,
Nohmi Takehiko,
Heddle John A.
Publication year - 2001
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/em.1036
Subject(s) - transgene , mutagen , biology , genetically modified mouse , genetics , in vivo , locus (genetics) , microbiology and biotechnology , gene , mutant , mutagenesis , somatic cell , mutation , ethylnitrosourea , carcinogen
The utility of any mutation assay depends on its characteristics, which are best discovered using model mutagens. To this end, we report further on the characteristics of the lambda‐based gpt delta transgenic assay first described by Nohmi et al. ([1996]: Environ Mol Mutagen 28:465–470). Our studies show that the gpt transgene responds similarly to other transgenic loci, specifically lacZ and cII, after treatment with acute doses of N ‐ethyl‐ N ‐nitrosourea (ENU). Because genetic neutrality is an important factor in the design of treatment protocols for mutagenicity testing, as well as for valid comparisons between different tissues and treatments, a time‐course study was conducted. The results indicate that the gpt transgene, like cII and lacZ, is genetically neutral in vivo. The sensitivities of the loci are also equivalent, as evidenced by spontaneous mutant frequency data and dose– response curves after acute treatment with 50, 150, or 250 mg/kg ENU. The results are interesting in light of transgenic target size and location and of host genetic background differences. Based on these studies, protocols developed for other transgenic assays should be suitable for the gpt delta. Additionally, a comparison of the gpt and an endogenous locus, Dlb‐1, within the small intestine of chronically treated animals (94 μg/mL ENU in drinking water daily) shows differential accumulation of mutations at the loci during chronic exposure. The results further support the existence of preferential repair at endogenous, expressed genes relative to transgenes. Environ. Mol. Mutagen. 37:297–303, 2001 © 2001 Wiley‐Liss, Inc.