High-efficiency deleter mice show that FLPe is an alternative to Cre-loxP

By mediating exclusive recombination in selected cell types, mouse strains expressing the site-specific recombinase Cre or FLP add a required, selective dimension to studies of mammalian gene function and cell fate. Having two highly active recombinases would advance such studies and elaborate new approaches for conditional genetic manipulations. Here we describe deleter mice harbouring FLPe, a recombinase variant isolated by protein evolution to have enhanced thermostability. We show that all FLPe deleter strains achieve maximum target gene excision in both somatic and germ cells, demonstrating that FLPe is highly effective in mice and an important alternative to, and complement for, the Cre-loxP system for in vivo genetic engineering.