Efficient FLP recombination in mouse ES cells and oocytes

We report an improved vector, pCAGGS-FLPe, for transient expression of the enhanced FLP recombinase in mouse ES cells and oocytes. In standard transfe ction experiments, about 6% of total ES colonies showed FLIP recombination, albeit with mosaicism within each colony. After microinjection of pCAGGS-F LPe into oocytes, about one-third of heterozygotic mice born showed complet e FLIP recombination. Thus pCAGGS-FLPe presents two practical options for r emoval of FRT cassettes in mice. (C) 2001 Wiley-Liss, Inc.