The Calb2-CreERT2 (CR-CreER or CR-CreERT2) knock-in allele was designed to both abolish Calb2 (calbindin 2; also called calretinin or CR) gene function and direct CreERT2 fusion protein expression to calretinin positive interneurons in the brain by the endogenous Calb2 promoter/enhancer elements. Cre-ERT2 fusion gene activity is inducible by tamoxifen administration.
Z. Josh Huang, Cold Spring Harbor Laboratory
Genetic Background | Generation |
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Allele Type | Gene Symbol | Gene Name |
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Targeted (Recombinase-expressing, Inducible) | Calb2 | calbindin 2 |
The Calb2-CreERT2 (CR-CreER or CR-CreERT2) knock-in allele was designed to both abolish Calb2 (calbindin 2; also called calretinin or CR) gene function and expresses CreERT2 fusion protein from the Calb2 promoter/enhancer elements. Cre-ERT2 fusion gene activity is inducible; observed following tamoxifen administration. As such, when CR-CreERT2 mice are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination will result in deletion of the floxed sequences in the CR-expressing cells of the offspring.
Heterozygous mice are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. The donating investigator reports that the phenotype of CR-CreER homozygous mice has not been assessed. However, CR-CreER homozygotes may be expected to exhibit the same phenotype as mice homozygous for other null mutations of this gene on a similar genetic background (impaired motor coordination, abnormal nervous system electrophysiology, and impaired long-term potentiation induction in dentate gyrus). Calretinin mRNA or protein expression from the CR-CreER mutant allele was not determined. The donating investigator also reports tamoxifen-inducible Cre recombinase activity recapitulates the endogenous calretinin expression pattern, but with moderate efficiency of induction. In olfactory bulb, the induction efficiency is higher. Tamoxifen-inducible Cre recombinase activity is not observed prior to tamoxifen treatment. Following tamoxifen administration, Cre recombinase activity is observed in calretinin positive interneurons in the brain. The donating investigators did not examine cre expression in tissues other than brain.
For characterization information, see images at the Allen Institute for Brain Science website (Calb2-CreERT2 images).
The Cre-ERT2 fusion protein consists of Cre recombinase fused to a triple mutant form of the human estrogen receptor which does not bind its natural ligand (17β-estradiol) at physiological concentrations but will bind the synthetic estrogen receptor ligands 4-hydroxytamoxifen (OHT or tamoxifen) and, with lesser sensitivity, ICI 182780. Restricted to the cytoplasm, Cre-ERT2 can only gain access to the nuclear compartment after exposure to tamoxifen. To counteract the mixed estrogen agonist effects of tamoxifen injections, which can result in late fetal abortions in pregnant mice, progesterone may be coadministered.
A targeting vector was designed to insert a CreERT2 fusion gene (Cre-ERT2; Cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain), an SV40 polyA signal, and an frt-flanked neo cassette into the initiation codon of the Calb2 (calbindin 2; also called calretinin or CR) locus. This construct was electroporated into C57BL/6-derived Bruce4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts and chimeric mice were bred with white C57BL/6 mice (harboring the Tyrc-2J mutation) to originate the colony. Mutant mice were bred with Actin-FLPe mice (on a C57BL/6 congenic background (N10); see Stock No. 005703) to remove the neo selection cassette. These Calb2-CreERT2 (CR-CreER or CR-CreERT2) mice were subsequently bred to white C57BL/6 mice for a few additional generations (and the FLPe transgene was removed) prior to sending to The Jackson Laboratory Repository. Upon arrival, mice were bred with C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish the Calb2-CreERT2 colony. These Calb2-CreERT2 mice may still be segregating at the Tyr locus.
Expressed Gene | cre/ERT2, Cre recombinase and estrogen receptor 1 (human) fusion gene, |
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Site of Expression | Following tamoxifen administration, Cre recombinase activity is observed in calretinin positive interneurons in the brain. |
Allele Name | targeted mutation 2.1, Z Josh Huang |
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Allele Type | Targeted (Recombinase-expressing, Inducible) |
Allele Synonym(s) | Calb2-CreER-KI , Calb2-CreERT2-KI; Calb2-CreERT2-KI; Calretinin-CreER-KI; CR-CreER-KI; CR-CreERT2-KI |
Gene Symbol and Name | Calb2, calbindin 2 |
Gene Synonym(s) | |
Expressed Gene | cre/ERT2, Cre recombinase and estrogen receptor 1 (human) fusion gene, |
Site of Expression | Following tamoxifen administration, Cre recombinase activity is observed in calretinin positive interneurons in the brain. |
Strain of Origin | C57BL/6 |
Chromosome | 8 |
Molecular Note | A targeting vector was designed to insert a CreERT2 fusion gene, an SV40 polyA signal, and anFRT-flanked neo cassette into the initiation codon of the Calb2 (calbindin 2; also called calretinin or CR) locus. This construct was electroporated into C57BL/6-derived embryonic stem (ES) cells. Mutant mice were bred with Actin-FLPe mice to remove the neo cassette, |
Mutations Made By | Z. Josh Huang, Cold Spring Harbor Laboratory |
When maintaining a live colony, heterozygous mice may be bred together, to wildtype siblings, or to C57BL/6J mice (Stock No. 000664). The donating investigator has not characterized the homozygous phenotype to date (December 2010).
When using the B6(Cg)-Calb2tm2.1(cre/ERT2)Zjh/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #013730 in your Materials and Methods section.
Facility Barrier Level Descriptions
Service/Product | Description | Price |
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Heterozygous or wildtype for Calb2<tm2.1(cre/ERT2)Zjh> |
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