STOCK Tg(Msx2-cre/ERT)27Alj/J

Stock number: 008847
Research areas: Developmental Biology Research, Research Tools

Description

These Msx2-CreERT transgenic mice have expression of a tamoxifen-inducible cre (Cre-ER^T) directed to apical ectodermal ridge (AER) of the developing limb by the -0.5 kbp promoter region from mouse homeobox msh-like 2 locus (Msx2). When these Msx2-CreERT transgenic mice are bred with mice containing a loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination is expected to result in deletion of the floxed sequences in AER of the developing limb.

Detailed description

Mice hemizygous for the Msx2-CreER^T transgene are viable and fertile, with expression of a tamoxifen-inducible Cre recombinase (Cre-ER^T) directed to apical ectodermal ridge (AER) of the developing limb by the -0.5 kb promoter region from the mouse homeobox msh-like 2 locus (Msx2). CreER^T fusion gene activity is inducible; observed following tamoxifen administration. When Msx2-CreER^T transgenic mice are bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination will result in deletion of the floxed sequences in the Msx2-expressing cells of the offspring (AER of the developing limb). The donating investigator has not determined the phenotype of homozygous mice to date (May 2012).

The Cre-ER^T fusion protein consists of Cre recombinase fused to a G521R mutant form of the human estrogen receptor binding domain 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-ER^T 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

The Msx2-CreERT transgene was designed with a 520 bp Msx2-AER promoter sequence (the -0.5 kbp promoter region immediately upstream from the mouse Msx2 start site that has been shown to direct expression to apical ectodermal ridge (AER) of the developing limb), a β-globin intron, CreERT fusion gene (Cre-ER^T; Cre recombinase fused to a G521R mutant form of the human estrogen receptor ligand binding domain), an 825 bp untranslated LacZtag sequence (to provide a tag for the transgene derived RNA), and an SV40 polyA signal. This transgene was injected into Swiss Webster zygotes. Mice from founder line 27, showing the strongest expression of CreERT in AER (as determined by RNA in situ hybridization), were established. These Msx2-CreERT transgenic mice were to Swiss Webster outbred mice for many generations. 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. In 2007, hemizygous males were used to freeze sperm. In 2012, frozen sperm was sent to The Jackson Laboratory Repository. Upon arrival, an aliquot of the frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664) to establish the The Jackson Laboratory Repository colony.

Allele

Symbol: Tg(Msx2-cre/ERT)27Alj
Name: transgene insertion 27, Alexandra L Joyner
MGI accession ID: MGI:4834769
Generation method: Transgenic
Attributes: Recombinase-expressing; Inducible
Marker symbol: Tg(Msx2-cre/ERT)27Alj
Marker name: transgene insertion 27, Alexandra L Joyner
Chromosome: UN
Strain of origin: Swiss Webster
Expressed genes: cre/ER,cre inducible estrogen receptor,bacteriophage P1/Human
Site of expression: expression of tamoxifen-inducible Cre recombinase (Cre-ERT) is directed to apical ectodermal ridge (AER) of the developing limb. When bred with mice containing loxP-flanked sequences, tamoxifen-inducible Cre-mediated recombination will result in deletion of the floxed sequences in the Msx2-expressing cells of the offspring (AER of the developing limb).
Molecular note: A transgenic construct was generated that contained cre/ERT, beta-globin intron, LacZtag, and SV40polyA coding sequences under control of an apical ectodermal ridge (AER)-specific 520 bp Msx2 promoter. The purified construct was injected into Swiss Webster zygotes. Nine founders were generated with eight transmitting the transgene. Four expressed cre/ERT in the apical ectodermal ridge (AER). Studies were performed using one line (no. 27) that showed the strongest expression.