B6J.B6N(Cg)-Cx3cr1^{tm1.1(cre)Jung}/J

Stock number: 025524
Product name: Cx3cr1-Cre
Research areas: Immunology, Inflammation and Autoimmunity Research, Research Tools

Description

Cx3cr1-Cre mice express Cre recombinase under the direction of the Cx3cr1 promoter in the mononuclear phagocyte system making them useful for fate-mapping studies of the monocyte and macrophage compartment, as well as microglia. These mice do not express endogenous Cx3cr1.

Detailed description

The Cx3cr1-Cre knock-in/knock-out allele has expression of Cre recombinase directed by Cx3cr1 (chemokine (C-X3-C motif) receptor 1) promoter regions. These mice do not express endogenous Cx3cr1. CX3CR1 is a chemokine receptor expressed in the mononuclear phagocyte system, as well as microglia. Homozygous mice are viable and fertile. When Cx3cr1-Cre are bred with mice containing loxP-flanked sequence, cre-mediated recombination will result in deletion of the floxed sequences in the cre-expressing cells of the offspring.

For example, when bred to B6.129X1-Gt(ROSA)26Sor^tm1(EYFP)Cos/J mice (Stock No. 006148), cre-mediated recombination results in yellow fluorescent protein expression in peritoneal, splenic and lung macrophages, and microglia and Kupffer cells. Some expression is also seen in circulating T and B lymphocytes, granulocytes and natural killer (NK) cells.

Depending on which floxed allele these mice are crossed to, significant rearrangement may occur in neurons as well as immune cells in the myeloid cell lineage. As adult neurons do not express CX3CR1, this is likely due to transient window of CX3CR1 promoter activity during neuronal development. For studies directed at understanding microglia function, use the conditional TAM-dependent CX3CR1-CreER mice (B6.129P2(C)-Cx3cr1^{tm2.1(cre/ERT2)Jung}/J; Stock No. 020940), in which no neuronal rearrangements are detected.

Development

Bacterial artificial chromosome (BAC) library (CHORI) was used to obtain a BAC containing the entire mouse Cx3cr1 (chemokine (C-X3-C motif) receptor 1) gene. This BAC was modified to replace the coding exon of Cx3cr1 with a Cre recombinase gene and a loxP-flanked neomycin resistance cassette. This BAC was electroporated into C57BL/6N-derived embryonic stem (ES) cells. Chimeras were made by ES cell aggregation with eight-cell stage embryos and chimeric mice were bred with Tg(Pgk1-cre)1Lni mice to delete the neo cassette. Resulting offspring were bred to remove the cre-expressing transgene, and progeny were bred with C57BL/6JOlaHsd inbred mice for at least 9 generations. Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J inbred mice (Stock No. 000664) for at least one generation to establish the colony.

Allele

Symbol: Cx3cr1^{tm1.1(cre)Jung}
Name: targeted mutation 1.1, Steffen Jung
MGI accession ID: MGI:5467983
Generation method: Targeted
Attributes: Recombinase-expressing
Marker symbol: Cx3cr1
Marker name: chemokine (C-X3-C motif) receptor 1
Chromosome: 9
Strain of origin: C57BL/6N
Expressed genes: cre,cre recombinase,bacteriophage P1
Site of expression: Cre recombinase is expressed in the mononuclear phagocyte system.
Molecular note: A cre recombinase cassette with a floxed neo was introduced into a BAC by RedE/T recombineering, replacing the coding exon, prior to homologous recombination to target the gene in ES cells. Cre-mediated recombination removed the selection cassette.