Related Experiment Videos
A recombination-based transgenic mouse system for genotoxicity testing
J R Murti1, K J Schimenti, J C Schimenti
1Jackson Laboratory, Bar Harbor, ME 04609.
Abstract:
It is well established that mutagens induce recombination in cultured cells and experimental organisms. Presumably, this is a consequence of the DNA-damage-triggering cellular-repair mechanisms. The relationship between recombination and mutagenicity has been exploited in submammalian organisms, such as yeast, to assay the ability of chemical agents and radiation to induce a form of recombination called gene conversion--the non-reciprocal transfer of genetic information. This work has demonstrated the efficacy of predicting mutagenicity on the basis of recombination induction. Here, we describe the utilization of a transgenic mouse system for efficient detection of germ-line gene-conversion events as a mutagen-screening tool. These mice contain two mutually defective reporter (lacZ) genes under the regulatory control of a spermatogenesis-specific promoter. A particular intrachromosomal gene conversion event must occur for the generation of functional lacZ activity. Conversion events are visualized by histochemical staining or flow cytometric analysis of transgenic spermatids. The highly mutagenic compound chlorambucil induced a several fold percentage-wise increase of lacZ-positive spermatids, whereas acrylamide, a weak genotoxin, produced no marked increase in converted spermatids. The results indicate that recombination-based transgenic mouse models for genotoxin screening present a viable option for inexpensive and rapid whole-animal mutagen testing. The particular mice we describe may ultimately prove to be a useful tool for identifying agents which can cause heritable genetic mutations in humans.
Insights
Researchers developed a transgenic mouse model to detect gene conversion, a type of genetic recombination. This system efficiently screens for mutagens, identifying chemicals that cause heritable genetic mutations.
Area of Science:
- Genetics and Molecular Biology
- Toxicology and Mutagenesis
Background:
- Mutagens are known to induce genetic recombination in various organisms.
- The relationship between mutagenicity and recombination, specifically gene conversion, has been utilized in yeast for mutagenicity assays.
- Existing methods require further development for efficient whole-animal mutagen screening.
Purpose of the Study:
- To develop and validate a transgenic mouse system for detecting germ-line gene conversion events.
- To utilize this system as a tool for efficient mutagen screening.
- To assess the potential of this model for identifying agents causing heritable genetic mutations.
Main Methods:
- Development of transgenic mice containing two defective lacZ reporter genes regulated by a spermatogenesis-specific promoter.
- Intrachromosomal gene conversion events were required for functional lacZ activity.
- Detection of gene conversion via histochemical staining or flow cytometry of transgenic spermatids.
Main Results:
- The highly mutagenic compound chlorambucil significantly increased the percentage of lacZ-positive spermatids.
- Acrylamide, a weak genotoxin, did not cause a marked increase in converted spermatids.
- The system demonstrated sensitivity in distinguishing between mutagenic and non-mutagenic agents.
Conclusions:
- Recombination-based transgenic mouse models offer a viable option for rapid, inexpensive, whole-animal mutagen testing.
- The described mouse system efficiently detects germ-line gene conversion events.
- This model holds promise for identifying agents capable of causing heritable genetic mutations in humans.