STOCK En1^{tm7(cre/ESR1)Alj}/J

Stock number: 007917
Research areas: Developmental Biology Research, Neurobiology Research, Research Tools

Description

En1-CreERT1 mutant mice harbor the Cre-ERT1 fusion gene under control of the endogenous engrailed 1 locus. When En1-CreERT1 mice are bred with mice containing a loxP-flanked sequence of interest, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the flanked sequences in En1-expressing tissues (including the mesencephalon and rhombomere 1, as well as the developing cerebellum, dermis, and limbs).

Detailed description

While mice heterozygous for this En1-CreERT1 mutation are viable and fertile, homozygotes die at birth. Because the Cre-ERT1 fusion gene is inserted between the transcriptional start site and the first exon of the engrailed 1 (En1) gene, tamoxifen-inducible cre activity is controlled by the endogenous En1 regulatory elements. The Cre-ERT1 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) and, with lesser sensitivity, ICI 182780. Restricted to the cytoplasm, Cre-ERT1 can only gain access to the nuclear compartment after exposure to OHT. To counteract the mixed estrogen agonist effects of tamoxifen injections, which can result in late fetal abortions in pregnant mice, progesterone may be coadministered. When these En1-CreERT1 mice are bred with mice containing a loxP-flanked sequence of interest, tamoxifen-inducible, Cre-mediated recombination will result in deletion of the flanked sequences in En1-expressing tissues (including the mesencephalon and rhombomere 1, as well as the developing cerebellum, dermis, and limbs).

Of note, these mice may also be useful in conjunction with other engrailed mutants (such as Stock No. 007912, Stock No. 007916, Stock No. 007918, Stock No. 007924, and Stock No. 007925).

Development

A targeting construct was designed with a CreERT1 fusion gene (Cre-ER^T1; Cre recombinase fused to a G400V/L539A/L540A triple mutation of the human estrogen receptor ligand binding domain) followed by a reverse-oriented loxP-flanked neo cassette. This construct was inserted between the transcriptional start site and first exon of the targeted gene (replacing the translational start site) via electroporation into 129S6/SvEvTac-derived W4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts, and chimeric males were bred to Black Swiss females. The resulting En1-CreERT1-neo heterozygotes were then bred to cre expressing mice (on a Swiss Webster genetic background) to remove the neo cassette, generating En1-CreERT1 offspring (with a single loxP site remaining after the Cre-ERT1 fusion gene). These En1-CreERT1 mutant mice were bred to Swiss Webster mice for many generations prior to arrival at The Jackson Laboratory. In addition, the donating investigator reports that although these mice harbor no additional mutant loci, they may contain incidental genetic background contributions as a result of past matings with other mutant mouse strains. Upon arrival, En1-CreERT1 mice were bred to 129S1/SvImJ (Stock No. 002448) for at least one generation to establish the colony.

Allele

Symbol: En1^{tm7(cre/ESR1)Alj}
Name: targeted mutation 7, Alexandra L Joyner
MGI accession ID: MGI:3528251
Generation method: Targeted
Attributes: Recombinase-expressing; Inducible
Marker symbol: En1
Marker name: engrailed 1
Chromosome: 1
Strain of origin: 129S6/SvEvTac
Expressed genes: cre/Esr1,Cre recombinase and estrogen receptor 1 fusion gene,
Site of expression: mesencephalon and rhombomere 1, as well as the developing cerebellum, dermis, and limbs (after induction)
Molecular note: A tamoxifen dependent form of cre recombinase (CreER) and a loxP-flanked neo in reverse orientation were inserted into the locus. The neo was removed in vivo via Cre-mediated recombination.