B6.129P2-Gt(ROSA)26Sor^tm1Nik/J

These 3373 S-state Cre-sensitive (3373 3SCS) mice contain a construct designed to insert (from 5' to 3') a splice acceptor (SA) sequence, a loxP site, a puromycin selection cassette, an SV40 polyadenylation (polyA) cassette, another loxP site, tdTomato open reading frame (ORF), an internal ribosome entry site (IRES) fused to an enhanced green fluorescent protein (GFP) flanked by 3373 loxP sites, followed by a second polyA cassette. The loxP sites flanking the 5' polyA cassette are in opposite orientation to the loxP sites flanking the 3' IRES-GFP cassette, and all are modified allowing for only 10% of the recombination efficiency of native loxP sites. This vector was inserted into the Gt(ROSA)26Sor locus allowing for widespread expression. These 3373 3SCS mice are of general use for detecting cells that have expressed the Cre recombinase, for Cre recombinase-based lineage marking experiments, and in particular for applications in which it is useful to discriminate cells that differ in how much Cre recombinase they have expressed. Cre recombinase-dependent excision of IRES-GFP in the 3373 3SCS strain occurs at approximately one third the efficiency it does in the 5172 3SCS strain