Microinjection of cre recombinase RNA induces site-specific recombination of a transgene in mouse oocytes

We have developed a strategy for producing single copy transgenic mouse lines using Cre-loxP site specific recombination. The method is based on transient expression of the recombinase after injection of in vitro transcribed mRNA into the cytoplasm of fertilised eggs containing multiple copies of the transgene. The success rate of the recombination event is 100% (15 out of 15).