Calb1^{tm1.1(folA/cre)Hze}

The targeting vector inserted a viral 2A oligopeptide (T2A, mediating ribosomal skipping) and a destabilized EGFP/Cre fusion gene (dgCre) inserted immediately downstream of the calbindin 1 translational STOP codon. The dgCre fusion gene (also called destabilized EGFP/Cre, DHFR-EGFP-Cre, hDHFR/EGFP/Cre or ecDHFR/EGFP/Cre) is an enhanced green fluorescent protein/Cre recombinase fusion gene with an N terminal fusion of the first 159 amino acids of the Escherichia coli K-12 strain chromosomal dihydrofolate reductase gene (DHFR or folA) harboring the G67S mutation and modified to also include the R12Y/Y100I destabilizing domain mutations. A PGK-neo-polyA cassette flanked by AttB and AttP sites was also part of the construct. Correctly targeted ES cells were injected into recipient blastocysts. The resulting chimeric animals were bred to PhiC31-expressing mice to delete the AttB/AttP-flanked sequences and replace it with the recombined AttB/AttP site (AttL). Trimethoprim-treatment is required to stabilize the cre protein. No EGFP is detected with or without induction. (J:243762)