Gt(ROSA)26Sor^{tm2(EGFP/cre)Alj}

A targeting vector was constructed to insert an SV40 splice acceptor sequence, an Frt-flanked PGK-neo cassette with polyA sequence, cDNA encoding an EGFP/cre fusion protein and 3 copies of the SV40 polyA signal into the first intron of Gt(ROSA)26Sor in ES cells. Flp expression will delete the neo cassette, permitting constitutive EGFP/cre expression in recombined cells and their progeny. In the absence of FLP recombinase, a very small percentage of cells may transiently expresses eGFPcre from the allele during embryonic development or in the adult. Furthermore, males spuriously express eGFPcre in their germline in the absence of FLP recombinase (although the eGFPcre protein is not transmitted to the fertilized egg). No eGFPcre expression is reported in the female germline prior to FLP recombination. (J:186310)