This strain may be useful in generating tissue-specific mutants of the exon 2 floxed allele of the aryl-hydrocarbon receptor (Ahr) for use in studies including teratogenesis and xenobiotic metabolism (including dioxin and PCB), Per-Arnt-Sim transcription factors, and fetal vascular development such as ductus venosus closure.
Christopher A Bradfield, University of Wisconsin-Madison
These mice possess loxP sites on either side of exon 2 of the targeted gene. Mice that are homozygous for this allele are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. Hepatic protein expression of the conditional allele (before exon 2 excision) is equivalent to wildtype by Western blot analysis. This strain may be useful in generating tissue-specific mutants of the floxed allele for use in studies including teratogenesis and xenobiotic metabolism (including dioxin and PCB), Per-Arnt-Sim transcription factors, and fetal vascular development such as ductus venosus closure.
When bred to a strain expressing Cre recombinase in hepatocytes (see Stock No. 003574 for example), this mutant mouse strain may be useful in studies of toxicology.
When bred to a strain expressing Cre recombinase in endothelial cells (see Stock No. 004128 for example), this mutant mouse strain may be useful in studies of vascular development.
A targeting vector was designed to place a loxP-flanked PGK-neo cassette immediately upstream of exon 2 of the endogenous gene, as well as insert a third loxP site downstream of exon 2. The targeting vector was built from a clone containing a 15 kb region of homology to the murine Ahr locus from a 129SvJ genomic library (129SvJ carries the Ahrd allele of the Ahr locus). The construct was electroporated into 129SvJ-derived GS1 embryonic stem (ES) cells (Genome Systems, St. Louis). Correctly targeted ES cells were injected into recipient blastocysts. Mice carrying the mutant allele (Ahrfxneo) were then bred to FVB/N mice with the EIIa-Cre transgene to remove the upstream PGK-neo cassette. After confirmation of PGK-neo excision, mice carrying loxP-flanked exon 2 were then bred to C57BL/6J-background mice for five generations to remove the EIIa-Cre transgene and produce the parental line (Ahrfx) - see SNP data below. Because the conditional Ahrfx allele was generated originally from 129SvJ genome (targeting vector and ES cells) that carry the lower affinity Ahrd allele, the donating investigator used a C57BL/6J strain congenic for DBA2-derived Ahrd allele to perform all backcrosses (see Stock No. 002921) prior to generating mice homozygous for the Ahrfx mutation.
In 2013-2014, a SNP (single nucleotide polymorphism) panel analysis with 29 markers covering all 19 chromosomes and the X chromosome was performed on the Ahrfx live colony (generation N5F3pF2pF2) at The Jackson Laboratory Repository. While 27 markers throughout the genome suggested a C57BL/6 genetic background, 2 markers on chromosome 17 were found to be segregating for FVB allele-type in some mice. These data suggest that the live colony was between ~87-93% C57BL/6 at that time.
|Allele Name||targeted mutation 3.1, Christopher A Bradfield|
|Allele Type||Targeted (Conditional ready (e.g. floxed), No functional change)|
|Allele Synonym(s)||Ahrfx; Ahrloxp|
|Gene Symbol and Name||Ahr, aryl-hydrocarbon receptor|
|Strain of Origin||129/Sv|
|Molecular Note||A neomycin resistance cassette was removed via cre-mediated recombination, leaving exon 2 floxed. Western blot of mutant livers confirmed protein was expressed as in wild-type animals.|
|Mutations Made By|| |
Christopher Bradfield, University of Wisconsin-Madison
When maintaining a live colony, these mice are maintained by breeding homozygotes.
When using the Ahrfx mouse strain in a publication, please cite the originating article(s) and include JAX stock #006203 in your Materials and Methods section.
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