B6(129S4)-Xcr1^{tm1.1(cre)Kmm}/J

Stock number: 035435
Product name: Xcr1^Cre
Research areas: Cancer Research, Immunology, Inflammation and Autoimmunity Research, Research Tools

Description

Xcr1^Cre knock-in mice express an mCherry fluorescent protein and an icre recombinase sequence under the direction of the Xcr1 promoter in conventional type 1 dendritic cells (cDC1).

In October 2022, expanded quality control screening at The Jackson Laboratory was concluded that determined the cre sequence in this mutant strain to be that of a codon-improved variant icre.

Detailed description

Xcr1^Cre knock-in mice express an mCherry fluorescent protein and a codon-improved cre recombinase sequence under the direction of the Xcr1 promoter. XCR1 encodes a G protein-coupled transmembrane chemokine receptor selectively expressed in conventional type 1 dendritic (cDC1) cells. An mCherry-T2A-Cre cassette, preceded by an IRES sequence, was inserted into the 3' UTR of the Xcr1 gene, maintaining expression of the endogenous Xcr1 gene. The viral T2A oligopeptide sequence mediates ribosomal skipping and allows for translation of the mCherry and cre sequences as separate proteins. Homozygous mice are viable and fertile. mCherry expression can be visualized by FACS and immunohistochemistry. When these mice 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. The donating investigator reports the possibility of some germline cre activity when bred to some floxed alleles.

When bred to R26R-EYFP mice (Stock No. 006148), mCherry and Cre activity are expressed specifically in cDC1, but not in cDC2 or other immune lineages. Xcr1 Cre efficiently deletes MHC-I and MHC-II surface expression from cDC1, but not other lineages, when crossed with mice carrying floxed alleles of β2-microglobulin (Stock No. 034858) and H2-Ab1 (Stock No. 013181), respectively. These mice may be useful when studying cellular interactions that mediate tumor rejection.

In October 2022, expanded quality control screening at The Jackson Laboratory was concluded that determined the cre sequence in this mutant strain to be that of a codon-improved variant icre.

Development

The Xcr1-mCherry-Cre targeting construct was designed to insert an internal ribosome entry site (IRES), followed by an mCherry fluorescent protein and a codon-improved cre recombinase sequence separated by a viral T2A oligopeptide that mediates ribosomal skipping, into the 3’ UTR of the X-C motif chemokine receptor 1 (Xcr1)gene. A frt-flanked neomycin resistance (neo) cassette was inserted 3’ of the cre sequence. This construct was electroporated into C57BL/6N-derived JM8.N4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and the resulting chimeric males were bred to C57BL/6NJ females. Resulting Xcr1^Cre mice were bred to B6N.129S4-Gt(ROSA)26Sortm1(FLP1)Dym/J (Stock No. 016226) mice to remove the neo cassette and offspring were crossed to remove the Flp gene. Mice were maintained by the donating lab on a C57BL/6NJ genetic background. Upon arrival at The Jackson Laboratory, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6NJ oocytes (Stock No. 005304).

In 2020, 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 males sent to The Jackson Laboratory Repository. Three of the 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating, including the rd8 recessive mutation associated with retinal degeneration on Chromosome 1 within the Crb1 locus. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6N;C57BL/6J genetic background.

In October 2022, expanded quality control screening at The Jackson Laboratory was concluded that determined the cre sequence in this mutant strain to be that of a codon-improved variant icre.

Allele

Symbol: Xcr1^{tm1.1(icre)Kmm}
Name: targeted mutation 1.1, Kenneth Murphy
MGI accession ID: MGI:6450161
Generation method: Targeted
Attributes: Recombinase-expressing; Reporter
Synonyms: Xcr1^Cre
Marker symbol: Xcr1
Marker name: chemokine (C motif) receptor 1
Marker synonyms: C motif-1/lymphotactin receptor; CCXCR1; GPR5; XCR1
Chromosome: 9
Strain of origin: C57BL/6N
Site of expression: Conventional type 1 dendritic cells (cDC1).
Molecular note: The targeting construct is designed to insert an internal ribosome entry site (IRES), followed by an mCherry fluorescent protein and the codon-improved cre recombinase (icre) sequence separated by a viral T2A oligopeptide that mediates ribosomal skipping, into the 3' UTR. An FRT-flanked neomycin resistance (neo) cassette was inserted 3' of the cre sequence. Flp-mediated recombination removed the FRT-flanked neo cassette