The Transgenic and In Vivo Mutagenesis Special Interest Group focuses on recent research measuring the frequency of mutation in tissues in whole animals. The Hprt lymphocyte assay has been a major tool for this research, which has been augmented by Aprt and Tk assays. However, these assays depend upon the ability to culture cells in vitro in order to apply the selection medium to identify mutants.
In the last 2 decades, transgenic animals, which contain tandem genomic insertions of bacterial genes have been used to measure in vivo mutation frequencies. These systems allow the identification of mutations in bacterial assays from any tissue from which sufficient DNA can be obtained to measure a mutant frequency. These transgenes include the following bacterial or viral targets: lacI (Big Blue , lacZ (MutaMouse ), cII (used with either Big Blue or MutaMouse); gpt delta, lacZ plasmid, and ΦX174 (Malling Mouse). Research with these tools has focused on validation of in vivo mutation, change in mutant frequency with age and tissue, and, particularly, the increase in mutant frequency with exogenous mutagens. Sequencing of mutants can add useful information in the interpretation of changes (or lack of change) in mutant frequencies.