B6(129S4)-Et(cre/ERT2)4Rdav/J

Stock number: 009573
Strain synonyms: C57BL/6-Et(cre/ERT2)4Rdav/J
Research areas: Neurobiology Research, Research Tools

Description

These mice express the tamoxifen-inducible Cre-ERT2 fusion protein (Cre-ER^T2) under the control of the promoter/enhancer regions surrounding the site where the enhancer trap transgene randomly inserted. These mice may be useful for generating conditional mutations for studying gain or loss of function and/or fate mapping in brain tissues.

Detailed description

Mice hemizygous for this enhancer trap transgene are viable and fertile, with expression of the Cre-ERT2 fusion gene under control of the promoter/enhancer regions surrounding the site where the enhancer trap transgene randomly inserted. Cre recombinase activity is observed in brain tissues following tamoxifen administration. The donating investigators may not have assessed expression in tissues other than brain. When these enhancer trap transgenic mice are bred with mice containing a loxP-flanked sequence of interest, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the floxed sequence(s) in cre-expressing tissues in the offspring.

For characterization information, see images at the Allen Institute for Brain Science website (Et(cre/ERT2)4Rdav images).

The Cre-ERT2 fusion protein (Cre-ER^T2) 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

An enhancer trap transgenic approach was used to generate these mice. The TK-bgi-cre:ERT2-bGHpA transgene was designed with a thymidine kinase minimal promoter, a beta-globin intron, a CreERT2 fusion gene (Cre-ER^T2; Cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain), and a bovine growth hormone polyA signal. This transgene was injected into C57BL/6J embryos. Founder mice (F0) from line 4 were bred to "C57 R26R" mutant mice from the Baylor College of Medicine (Gt(ROSA)26Sor^tm1Sor mice; similar to, but perhaps not as backcrossed as Stock No. 003474). The donating investigator reports that Cre-positive transgenic pups were bred to C57BL/6 mice or "C57 R26R" (see SNP note below) to maintain the colony. Upon arrival, transgenic mice were selectively bred to C57BL/6J inbred mice (Stock No. 000664) to remove the Gt(ROSA)26Sor^tm1Sor mutation.

A single nucleotide polymorphism (SNP) assay predicted these mice were 99% congenic onto the C57BL/6 genetic background (1 of 141 markers was not C57BL/6-allele type (on chromosomes 11). A 32 SNP panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, at least 2 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.

Allele

Symbol: Et(cre/ERT2)4Rdav
Name: enhancer trap 4, Ron Davis
MGI accession ID: MGI:3852322
Generation method: Transgenic
Attributes: Recombinase-expressing; Inducible
Marker symbol: Et(cre/ERT2)4Rdav
Marker name: enhancer trap 4, Ron Davis
Chromosome: UN
Strain of origin: C57BL/6J
Expressed genes: cre/ERT2,Cre recombinase and estrogen receptor 1 (human) fusion gene,
Site of expression: Cre recombinase activity is observed in brain tissues following tamoxifen administration.
Molecular note: An enhancer trap transgenic approach was used to generate these mice. The TK-bgi-cre:ERT2-bGHpA transgene was designed with the thymidine kinase (TK) minimal promoter driving a cre-ER^T2 fusion gene (cre recombinase fused to a G400V/M543A/L544A triple mutation of the human estrogen receptor ligand binding domain). A beta globin intron separates the promoter from the cre gene and the bovine growth hormone polyadenylation signal follows the cre sequence. This transgene was injected into C57BL/6J embryos. Founder line 4 was established on a C57BL/6J genetic background.