N-ethyl-N-nitrosourea mutagenesis produced a small number of mice with altered plasma electrolyte levels

Analysis of the sex-specific variability of blood parameters in C3H inbred mice by using data from a long-term, high-throughput project

Mice are important models for biomedical research by providing the possibility of standardizing genetic background and environmental conditions, which both affect phenotypic variability. Use of both sexes in experiments is strongly recommended because of possible differences in the outcome. However, sex-specific phenotypic variability is discussed with regard to putative consequences on the group size which is necessary for achieving valid and reproducible results. Here, we retrospectively analyzed the sex-specific variability of 25 blood parameters of C3H inbred mice in two different mouse facilities withinthe long-term, high-throughput Munich ENU mouse mutagenesis project. Using the 95 % data range, data of4,780-20,706 mice per parameter were analyzed and resulted in ratios of the coefficient of variation (= female CV / (female CV + male CV)) from 0.44 to 0.58 for the 25 parameters, with an overall mean of 0.51 in both facilities. Together with data analyses of three additional, smaller studies with 72-247 animals per parameter examined and various genetic backgrounds (inbred strains, F1 hybrids) included, hints for reproducible sex-specific variability were observed for particular parameters. Thus, the overall analysis comprising all 25 clinical chemical and hematological parameters of the standardized, long-term analysis of a high number of group housed, young adult, twelve-week-old C3H inbred mice showed no evidence for substantial sex-specific variability. The results may provide a basis for the examination of sex-specific variability in particular blood parameters.

Random mutagenesis of the mouse genome: a strategy for discovering gene function and the molecular basis of disease

Mutagenesis of mice with N-ethyl-N-nitrosourea (ENU) is a phenotype-driven approach to unravel gene function and discover new biological pathways. Phenotype-driven approaches have the advantage of making no assumptions about the function of genes and their products and have been successfully applied to the discovery of novel gene-phenotype relationships in many physiological systems. ENU mutagenesis of mice is used in many large-scale and more focused projects to generate and identify novel mouse models for the study of gene functions and human disease. This review examines the strategies and tools used in ENU mutagenesis screens to efficiently generate and identify functional mutations.

Using ENU mutagenesis for phenotype-driven analysis of the mouse

The use of mutagenesis in invertebrates to generate phenotypic variants has a long and productive history. Despite the conclusive demonstration by Russell and colleagues in the 1970s that the chemical N-ethyl-N-nitrosourea (ENU) is a highly effective mutagen in mice, the application of phenotypic-driven mutagenesis as a method to study mammalian biology proceeded slowly. With the development of tools for genomic analysis, the task of positional cloning ENU-induced mutations has become quite feasible, and this approach has recently been widely applied and highly productive. It has specifically lived up to its theoretical utility as means to provide insight into the biological roles of genes that is not biased by presumptions of their function. While the power of this approach is indisputable, the effort necessary for its success remains substantial, requiring careful attention to aspects including ENU treatment, mouse husbandry, screen assay design, genetic mapping, positional cloning, and mutation validation. In this chapter we discuss practical aspects of implementing a phenotype-driven analysis of an ENU-mutagenized mouse population.