Genome-tagged mice (GTM): two sets of genome-wide congenic strains

An important approach for understanding complex disease risk using the mouse is to map and ultimately identify the genes conferring risk. Genes contributing to complex traits can be mapped to chromosomal regions using genome scans of large mouse crosses. Congenic strains can then be developed to fine-map a trait and to ascertain the magnitude of the genotype effect in a chromosomal region. Congenic strains are constructed by repeated backcrossing to the background strain with selection at each generation for the presence of a donor chromosomal region, a time-consuming process. One approach to accelerate this process is to construct a library of congenic strains encompassing the entire genome of one strain on the background of the other. We have employed marker-assisted breeding to construct two sets of overlapping congenic strains, called genome-tagged mice (GTMs), that span the entire mouse genome. Both congenic GTM sets contain more than 60 mouse strains, each with on average a 23-cM introgressed segment (range 8 to 58 cM). C57BL/6J was utilized as a background strain for both GTM sets with either DBA/2J or CAST/Ei as the donor strain. The background and donor strains are genetically and phenotypically divergent. The genetic basis for the phenotypic strain differences can be rapidly mapped by simply screening the GTM strains. Furthermore, the phenotype differences can be fine-mapped by crossing appropriate congenic mice to the background strain, and complex gene interactions can be investigated using combinations of these congenics.