Using a conventional ES line to engineer mice that already carry transgenes or knockouts, or require specific genetic backgrounds for desired phenotypes, can require extensive backcrossing to produce isogenic lines. A custom ES cell line derived from the specialized mouse line can greatly simplify introgression of new genetic loci.

We have produced custom ES lines for corporate and academic partners. We have done large projects, generally for 10 or more mouse strains, as well as small projects for single mouse lines.