C57BL/6-Ahr^tm1Lgzh/J

Stock number: 040918
Product name: Ahr^CAIR
Research areas: Cancer Research, Immunology, Inflammation and Autoimmunity Research, Research Tools

Description

Ahr^CAIR knock-in/knock-out mice express a Cre-inducible constitutively active aryl hydrocarbon receptor (CA-Ahr; lacking the PAS-B domain) and enhanced green fluorescent protein (EGFP). In the absence of Cre recombinase, the Ahr^CAIR allele functions as a null allele. In the presence of Cre recombinase, these mice express a FLAG-CA-Ahr-IRES-EGFP fusion protein, allowing for the monitoring of AHR activity in a cell/tissue specific manner as directed by the Cre promoter. This strain may be useful in the study of toxicology and immunology.

Detailed description

The Ahr gene encodes the aryl-hydrocarbon receptor protein that functions as a sensor for both environmental and physiological ligands, and is also associated with immunological responses to xenobiotic compounds and pollutants.

The Ahr^CAIR knock-in/knock-out (KI/KO) allele has a floxed STOP cassette followed by a constitutively active form of Ahr (CA-Ahr) sequence and an enhanced green fluorescent protein (EGFP) inserted into Ahr translational exon 1. The construct is designed to prevent transcription of the endogenous Ahr locus in the absence of Cre recombinase, resulting in a null allele. Prior to exposure to Cre recombinase, mice heterozygous for the Ahr^CAIR allele are viable and fertile with no reported gross physical or behavioral abnormalities. The donating investigator reports that Ahr^CAIR mice have no detectable expression of Ahr or EGFP transcript from homozygous Ahr^CAIR mice in the absence of Cre recombinase. Homozygous Ahr^CAIR have defects in innate lymphoid cells in the gut, similar to Ahr-null mice.

Following exposure to Cre recombinase, CA-Ahr and EGFP protein are expressed in cells/tissues as directed by the Cre promoter. For example, when bred to germline Cre-expressing mice (E2A-Cre; see Stock No. 003724), the resulting heterozygous Ahr^CAIR/+ mice can be used to investigate the role of Ahr expression in the development and trafficking of regulatory T cells in the gut (Ye et al. 2017).

Development

The Ahr^CAIR knock-in/knock-out (KI/KO) allele was generated by insertion of a knock-in fragment into exon 1 of the aryl-hydrocarbon receptor (Ahr). The knock-in fragment was generated by cloning a FLAG-tagged Ahr cDNA with deletion of amino acids 278-423 (referred to as CA-Ahr) into a pIRES2-eGFP plasmid (Clontech). The final targeting construct includes a loxP-flanked STOP cassette (Pgk-neo-tpA), the FLAG-tagged CA-Ahr cDNA sequence, an internal ribosome entry site (IRES), and an enhanced green fluorescent EGFP sequence. The inserted Flag-CA-Ahr-IRES-EGFP sequence is abbreviated as CAIR by the donating laboratory. The construct was electroporated into C57BL/6N-derived PRX-B6N embryonic stem (ES) cells. ES cells were injected into C57BL/6J-Tyr^c-2J mice (albino B6; Stock No.000058) blastocysts, and chimeric males were mated to albino B6 mice to confirm germline transmission. Resulting Ahr^CAIR KI/KO mice were maintained on a C57BL/6N genetic background by the donating laboratory. Upon arrival at The Jackson Laboratory Repository, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304).

Allele

Symbol: Ahr^tm1Lgzh
Name: targeted mutation 1, Liang Zhou
MGI accession ID: MGI:6343215
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed); Reporter; Constitutively active; Epitope tag
Synonyms: Ahr^CAIR; Ahr^{stop-Flag CA-Ahr-IRES-GFP}
Marker symbol: Ahr
Marker name: aryl-hydrocarbon receptor
Marker synonyms: Ah; Ahh; Ahre; bHLHe76; dioxin receptor; FVH3; In; RP85
Chromosome: 12
Strain of origin: C57BL/6NTac
Molecular note: A floxed STOP, Flag tag, Ahr cDNA with deletion from aa 278 to aa 423, IRES sequence, and GFP reporter gene were inserted into exon 1. Cre-mediated recombination is required to achieve expression of the modified cDNA.