Using Targeted Large Deletions and High-EfficiencyN-Ethyl-N-nitrosourea Mutagenesis for Functional Analyses of the Mammalian Genome

The Human Genome Project has generated nucleotide sequences from an estimated 80,000 to 100,000 genes, only a small fraction of which have a known role. Nucleotide sequence information alone is insufficient to predict gene function. One of the most powerful ways of revealing gene function, as demonstrated in bacteria, worms, yeast, and flies, is to generate mutations and characterize them at both the phenotypic and the molecular levels. Given the physiological and anatomical parallels between mouse and human, genotype–phenotype relationships established in mice can be extrapolated to human syndromes. A new method is described for functional genetic analyses in the mouse that uses loxP/Cre engineering to generate coat color-tagged large deletions. The haploid regions can then be dissected by mutagenesis withN-ethyl-N-nitrosourea in phenotype-driven screens to obtain functional information on genes in any desired region of the mouse genome.