Discovery and functional characterization of new genes by large scale ENU mutagenesis in mice.

The most important tool to obtain insight into the function of genes is the use of mutant model organisms. Homologous recombination in embryonic stem cells allows the systematic production of mouse mutants for any gene that has been cloned. Gene trap strategies have been designed to interrupt even unknown genes which are tagged by the inserted vector and can be characterized structurally and functionally. Complementary to such 'gene-driven' approaches, 'phenotype-driven' approaches are necessary to identify new genes or gene products through a search for mutants with specific defects, e.g. in immune function and resistance to infectious diseases. Mutagenesis using the alkylating agent N-ethyl-N-nitrosourea (ENU) is a powerful approach for the production of mouse mutants (mainly point mutations). ENU mutagenizes - among other cells - premeiotic spermatogonia of F0 males which can be bred to produce a large number of G1 offspring or G3 pedigrees, respectively. It has been demonstrated for certain loci that the frequency of mutant recovery is about 1/1000 (recessive mutation) or 1/5000 (dominant mutation) for a specific locus that can be scored phenotypically, although strain as well as dosage and treatment regime do influence the mutagenesis rate. The mutants produced will be mainly hypomorphic, although gain-of-function and complete loss-of-function mutants can also be expected. These mutants are important tools for the identification of candidate genes for animal health, offering new strategies for the prevention, diagnosis, and therapy of diseases