B6(Cg)-Pvalb^{tm1(cre/ERT2)Zjh}/J

Stock number: 010777
Product name: Pv-CreER
Research areas: Neurobiology Research, Research Tools

Description

The Pv-CreERT2 knock-in allele in these mice both abolishes parvalbumin gene function and expresses the CreERT2 fusion protein directed to parvalbumin positive neurons in neocortex and cerebellum by the endogenous Pvalb promoter/enhancer elements.

Detailed description

The Pv-CreERT2 (Pvalb-CreERT2) knockin/knockout allele both abolishes parvalbumin (Pvalb; also called PV or Pva) gene function and expresses a CreER^T2 fusion protein (creERT2 fusion protein) from the Pvalb promoter/enhancer elements. Homozygous mice are viable and fertile. Homozygotes are expected to have a knockout phenotype similar to other null mutations of this gene and may exhibit muscle contractile, mitochondrial, and/or Purkinje cell abnormalities. Cre-ERT2 fusion gene activity is inducible; observed following tamoxifen administration. As such, when Pv-CreERT2 mice are bred with mice containing loxP-flanked sequence(s), tamoxifen-inducible Cre-mediated recombination will result in deletion of the floxed sequence(s) in the Pvalb-expressing cells of the offspring.

The donating investigator reports tamoxifen-inducible Cre recombinase activity recapitulates the endogenous Pvalb expression pattern, but with low efficiency of induction. They report tamoxifen-inducible Cre recombinase activity is observed in parvalbumin positive neurons in neocortex and cerebellum, and did not examine cre expression in tissues other than brain.

For characterization information, see images at the Allen Institute for Brain Science website (Pvalb-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.

Development

A targeting vector was designed to insert a CreER^T2 fusion gene (Cre-ER^T2; 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 Pvalb (parvalbumin; also called PV or Pva) gene. 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 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. Pv-CreERT2 mice were subsequently bred together for many generations prior to arrival at The Jackson Laboratory. Upon arrival, mice were bred with C57BL/6J inbred mice (Stock No. 000664) for at least one generation (and the FLPe transgene was selectively bred away) to establish the Pv-CreERT2 colony.

SNP (single nucleotide polymorphism) analysis performed by The Jackson Laboratory revealed that the Donating Investigator used C57BL/6N (2 of 5 markers segregating) in the development of the strain.

Allele

Symbol: Pvalb^{tm1(cre/ERT2)Zjh}
Name: targeted mutation 1, Z Josh Huang
MGI accession ID: MGI:4365738
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible
Marker symbol: Pvalb
Marker name: parvalbumin
Chromosome: 15
Strain of origin: C57BL/6
Expressed genes: cre/ERT2,Cre recombinase and estrogen receptor 1 (human) fusion gene,
Site of expression: tamoxifen-inducible Cre recombinase activity is observed in parvalbumin positive neurons in neocortex and cerebellum.
Molecular note: 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 Pvalb (parvalbumin; also called PV or Pva) gene. Mutant mice were bred with Actin-FLPe mice (on a C57BL/6 congenic background) to remove the neo selection cassette.