Analysis of spontaneous and induced mutations in transgenic mice using a lambda ZAP/lacI shuttle vector

Area of Science:

• Toxicology
• Genetics
• Molecular Biology

Background:

• Developing reliable in vivo mutagenesis assays is crucial for assessing chemical safety.
• Existing methods often lack the sensitivity or direct applicability to whole-animal responses.

Purpose of the Study:

• To establish a short-term in vivo mutagenesis assay in transgenic mice.
• To evaluate the mutagenicity of various chemical compounds using this novel system.
• To characterize the types of mutations induced by chemical exposure in vivo.

Main Methods:

• Utilized transgenic mice harboring a lacl target gene within a lambda ZAP shuttle vector.
• Recovered the target gene from mouse genomic DNA after chemical exposure.
• Identified mutations by infecting E. coli with lambda phage and plating on Xgal indicator plates.
• Performed sequence analysis on mutant clones to determine mutation types.

Main Results:

• The assay detected significant induction of mutations (up to 74-fold) for compounds like benzo(a)pyrene and N-ethyl-N-nitrosourea.
• Sequence analysis revealed base substitutions as the primary spontaneous mutations in mice, differing from E. coli models.
• Benzo(a)pyrene exposure resulted exclusively in transversions, aligning with its known mutagenic mechanism.

Conclusions:

• The developed lacl transgenic mouse model provides a sensitive platform for in vivo mutagenicity testing.
• This system allows for the extrapolation of in vitro data to whole animals.
• The assay offers insights into tissue-specific effects of mutagenic compounds.