C57BL/6N-Ighg1^{em2(cre,-dre/ERT2)Rsky}/J

Stock number: 040961
Product name: Cγ1-CDE
Research areas: Research Tools

Description

Cγ1-CDE knock-in mice have a cassette containing IRES-Cre_T2A_DreERT2 inserted into the 3'-UTR of the Ighg1 or Cγ1 gene. They are useful for sequential recombination of loxP sites and tamoxifen-induced recombination of rox sites in germinal center B-cells.

Detailed description

Cγ1-CDE knock-in mice have a cassette containing IRES-Cre_T2A_DreERT2 inserted into the 3'-UTR of the Ighg1 or Cγ1 gene. These mice express Cre and tamoxifen-inducible Dre/ERT2 in germinal center B-cells. Restricted to the cytoplasm, Dre/ERT2 can only gain access to the nuclear compartment after exposure to tamoxifen. When these mice are bred with mice containing loxP-flanked sequence, Cre-mediated recombination will result in deletion of the floxed sequences. When subsequently bred with mice containing rox-flanked sequence, tamoxifen-inducible Dre-mediated recombination will result in deletion of the roxed sequences. These mice are useful for sequential recombination of loxP sites and tamoxifen-induced recombination of rox sites in germinal center B-cells.

Homozygous mice are viable and fertile. The donating investigator reports in the absence of tamoxifen, no Dre recombination is detected.

When Cγ1-CDE mice are bred with mice containing a rox-controlled, Dre-inducible Foxo1 allele (Stock No. 040962), Foxo1 expression from the allele is inactivated in the absence of Dre activity. In the presence of tamoxifen, recombination of rox sites removes the STOP cassette, leading to a rescue of the previously induced FOXO1 deficiency. This system is also useful when combined with Foxo1-floxed mice (Stock No. 037499) for Cre-mediated deletion of Foxo1 and the subsequent time-controlled, Dre-mediated FOXO1 re-expression and functional rescue in germinal center B-cells.

Of note, the donating investigator has donated similar strains including Cγ1-cre mice (Stock No. 010611) and Cγ1-CreERT2 mice (Stock No. 032860).

Development

sgRNAs were designed to target the 3' UTR of the immunoglobulin heavy constant gamma 1 (G1m marker) (Ighg1 or Cγ1) gene for insertion of a cassette containing IRES-Cre_T2A_DreERT2 (a cre recombinase and a dre recombinase sequence fused to a human estrogen receptor ligand binding domain). sgRNA, the cas9 protein, and a donor plasmid were introduced into C57BL/6N-derived embryos with well-recognized pronuclei. Injected embryos were transferred to pseudopregnant females. Resulting Cγ1-CDE knock-in mice were identified by PCR and sequencing, and correctly targeted offspring were further bred to Foxo1^stopRox mice (Stock No. 040962) and this colony of mice was bred to C57BL/6NCrl mice for at least 3 generations by the donating laboratory. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304). The Foxo1^stopRox allele was bred out of this colony and is available as Stock No. 040962.

Allele

Symbol: Ighg1^{em2(cre,-dre/ERT2)Rsky}
Name: endonuclease-mediated mutation 2, Klaus Rajewsky
MGI accession ID: MGI:8245160
Generation method: Endonuclease-mediated
Attributes: Recombinase-expressing; Inducible
Synonyms: Cgamma1-CDE
Marker symbol: Ighg1
Marker name: immunoglobulin heavy constant gamma 1 (G1m marker)
Marker synonyms: IgG1; IgG3; Igh-4
Chromosome: 12
Strain of origin: C57BL/6N
Molecular note: sgRNAs were designed to target the 3' UTR of the immunoglobulin heavy constant gamma 1 (G1m marker) (Ighg) gene for insertion of a cassette containing IRES-Cre_T2A_DreERT2 (a cre recombinase and a dre recombinase sequence fused to a human estrogen receptor ligand binding domain).