Site-specific transgenesis in Xenopus.

Transgenesis is an essential, powerful tool for investigating gene function and the activities of enhancers, promoters, and transcription factors in the chromatin environment. In Xenopus, current methods generate germ-line transgenics by random insertion, often resulting in mosaicism, position-dependent variations in expression, and lab-to-lab differences in efficiency. We have developed and tested a Xenopus FLP-FRT recombinase-mediated transgenesis (X-FRMT) method. We demonstrate transgenesis of Xenopus laevis by FLP-catalyzed recombination of donor plasmid cassettes into F(1) tadpoles with host cassette transgenes. X-FRMT provides a new method for generating transgenic Xenopus. Once Xenopus lines harboring single host cassettes are generated, X-FRMT should allow for the targeting of transgenes to well-characterized integration site(s), requiring no more special reagents or training than that already common to most Xenopus labs.