These transgenic mice express Cre recombinase under the control of the mouse SRY-box containing gene 2 promoter. The transgene integrated into an intron of Edil3 (EGF-like repeats and discoidin I-like domains 3). The insertion results in a functional knock-out of Edil3 in homozygous mice. Mice hemizygous for the Sox2Cre transgene are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. When these transgenic mice are bred with mice containing loxP-flanked sequences, Cre-mediated recombination will result in deletion of the floxed sequences in Sox2-expressing tissues in the offspring. Specifically, Cre recombinase activity is detected in the epiblast cells at embryonic day 6.5, with little or no activity in other cells at gastrulation. Some activity is also detected in extra embryonic derivatives of the epiblast, the yolk sac mesoderm and amnion. No Cre recombinase activity is detected in primitive endoderm derived tissues, visceral endoderm. The phenotype of homozygous mice has not been characterized to date (April 2011). These Sox2Cre transgenic may be useful for generating epiblast-derived specific conditional mutations. Transgene expression is active in the female germline. Offspring arising from a hemizygous transgenic female will exhibit Cre recombinase activity, regardless of genotype. This maternal inheritance effect, due to female germline expression of the transgene, can provide a rapid and efficient breeding mechanism for generating null animals. The Jackson Laboratory 2024, used with permission.