This transgenic strain expresses a variant of the Saccharomyces cerevisiae FLP1 recombinase gene under the direction of the human ACTB promoter. The FLPe recombinase variant exhibits enhanced thermostability with recombination activity being four-fold and ten-fold that of wildtype FLP at 37C and 40C, respectively. Mice that are hemizygous for the transgenic allele are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Recombinase activity is detected in a wide variety of tissues (spinal cord, heart, gonad, adrenal) as early as embryonic day 10.5. This deleter strain is a suitable alternative to, and complement with the Cre-loxP system for in vivo genetic engineering. The Jackson Laboratory 2024, used with permission.