http://www.creative-animodel.com/Animal-Model-Development/ES-cell-based-gene-overexpression.html

In addition to pronuclear microinjection, foreign DNA can be introduced into embryonic stem cells (ES cells). Creative Animodel has developed a novel ES cell-based technology that reduces the risks associated with the development of transgenic mouse line by DNA pronuclear random integration. This approach allows the generation of a high number of founders with validated characteristics (no truncated transgene and low, medium or high transgene copy number).

Once your model is generated, Creative Animodel can breed, test, characterize and/or distribute it on your behalf, drawing on six decades of breeding and worldwide distribution experience for an efficient, single-source solution.