B6(Cg)-Chrna7^tm1.1Ehs/YakelJ

Stock number: 026965
Product name: α7nAChR^flox
Research areas: Neurobiology Research, Research Tools

Description

α7nAChR^flox mice have loxP sites flanking exon 4 of the Chrna7 gene. This strain may be useful for generating conditional mutations in studies of possible therapeutic targets for cognitive defects and applications related to the cholinergic anti-inflammatory pathway.

This floxed allele acts as a hypomorph - see Detailed Description for more information.

Detailed description

The ligand-gated ion channel alpha7 nicotinic acetylcholine receptor, encoded by the Chrna7 gene, is widely expressed throughout the CNS in neurons and glial cells, and facilitates fast synaptic signal transmission. alpha7 nAChR is associated with epilepsy, Alzheimer's disease and schizophrenia.

These α7nAChR^flox mice possess loxP sites on either side of exon 4 of the targeted gene. Mice that are homozygous for this allele are viable and fertile - however homozygous mice exhibit decreased breeding performance. This floxed allele acts as a hypomorph - see additional information below.

When α7nAChR^flox are exposed to Cre recombinase, exon 4 is deleted in the cre-expressing tissues. Deletion of exon 4 yields an unstable mRNA gene product.
When bred to a strain with Cre recombinase expression in astrocytes (see Stock No. 012887 or Stock No. 024098 for example), this mutant mouse strain may be useful in studies of attention, learning and memory.

In 2020, analysis performed by The Jackson Laboratory suggests the α7nAChR^flox allele also acts as a hypomorph. Western blot of brain lysates using two different mouse Chrna7 antibodies show Chrna7 levels are ~50% reduced in heterozygotes and homozygotes as compared to wildtype littermates. In addition, PCR and Sanger sequencing shows intact loxP sites flanking exon 4 where expected.

Development

A loxP site flanked targeting vector containing a FRT site flanked PGK-Neo selection cassette was utilized in the construction of this mutant. This selection cassette was inserted downstream of exon 4 of the targeted gene, and another loxP site was inserted upstream of exon 4. This construct was electroporated into C57BL/6NTac derived B6-3 embryonic stem (ES) cells which were transiently transfected with a FLP1 recombinase vector to remove the selection cassette. ES cells that had successfully undergone FLP1 recombination and no longer retained the cassette but did retain the loxP-flanked exon 4 were injected into albino C57BL/6 (C57BL/6J-Tyr^c-2J/J) blastocysts. The resulting chimeric male animals were backcrossed to C57BL/6J by the donating lab (see SNP note below). The strain was then cryopreserved as sperm, and recovered on C57BL/6J (Stock No. 000664) at least once to establish the colony.

In 2019 a 48 SNP (single nucleotide polymorphism) panel analysis, with 43 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. While the 43 markers throughout the genome suggested a C57BL/6 genetic background, 3 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.

In 2020, PCR and Sanger sequencing analysis performed by The Jackson Laboratory shows intact loxP sites flanking exon 4 where expected.

Allele

Symbol: Chrna7^tm1.1Ehs
Name: targeted mutation 1.1, National Institute of Environmental Health Science
MGI accession ID: MGI:5620283
Generation method: Targeted
Attributes: Conditional ready (e.g. floxed)
Marker symbol: Chrna7
Marker name: cholinergic receptor, nicotinic, alpha polypeptide 7
Chromosome: 7
Strain of origin: C57BL/6NTac
Molecular note: The targeting vector contains a loxP site 290 bp upstream of exon 4 and loxP site followed by a FRT-flanked PGK-Neo selection cassette 380 bp downstream of exon 4. Flp-mediated recombination removed the FRT-flanked neo cassette leaving exon 4 floxed.