The Cr-IRES-Cre (Calb2-IRES-Cre) allele harbors an internal ribosome entry site and Cre recombinase in the 3' UTR of the Calb2 locus (calbindin 2; also called calretinin or CR). As such, it is designed to have the endogenous Calb2 promoter/enhancer elements directing cre expression to calretinin interneurons in the brain and cortex. When Calb2-IRES-Cre mice are bred with mice containing loxP-flanked sequences, Cre-mediated recombination will result in deletion of the floxed sequences in the Calb2-expressing cells of the offspring. Calb2 expression from the Calb2-IRES-Cre allele has not been evaluated. Additional phenotype information described below.
In 2009, the donating investigator reported that Cre recombinase activity is specific and efficient (largely recapitulates the endogenous Calb2 expression pattern with highly efficient recombination). They did not examine cre expression in tissues other than brain. Calb2 expression from the Calb2-IRES-Cre allele was not evaluated. They also reported that homozygous mice are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities.
For characterization information, see images at the Allen Institute for Brain Science website (Calb2-IRES-Cre images).
If the recombinase activity pattern of this allele is further characterized by the Genetic Resource Science group at The Jackson Laboratory, such findings will be reported on the Mouse Genome Informatics (MGI) Allele Detail entry (Calb2tm1(cre)Zjh). This same information would also be found searching the MGI Recombinase Activity database.
