B6.Cg-Cd300lf^tm1Jco/J

Stock number: 031392
Product name: C57BL/6 Cd300lf^-/-
Research areas: Apoptosis Research, Cancer Research, Immunology, Inflammation and Autoimmunity Research, Research Tools

Description

Cd300f^-/- C57BL/6 mice (also called C57BL/6 Cd300lf^-/- mice) have a knock-out allele of the CD300 molecule like family member F (CD300LF or CLM-1) locus. These mice may be useful in studying efferocytosis (the phagocytic clearance of dying/apoptotic cells and dead/necrotic cells) by macrophages and dendritic cells, as well as novel approaches to cancer immunotherapy.

Detailed description

Homeostasis requires efferocytosis - the immunologically silent clearance of dying/dead cells (e.g., apoptotic or necrotic cells) by phagocytes. Apoptotic cells (ACs) display various "eat-me" signals on their surface that are recognized by phagocytes - the most well-known "eat-me" signal is phosphatidylserine (PS). The CD300 molecule like family member F (CD300LF or CLM-1) is a PS receptor that functions to positively regulate efferocytosis in macrophages (MΦs), but inhibit efferocytosis in dendritic cells (DCs). CD300LF may also function as a dendritic cell checkpoint receptor (analogous to T cell checkpoint receptors like PD-1 and CTLA-4) and therefore may provide novel approaches to cancer immunotherapy.

These Cd300f^-/- C57BL/6 mice (also called C57BL/6 Cd300lf^-/- mice) harbor a CD300LF knock-out allele. Both heterozygous and homozygous mice are viable and fertile with normal fertility - and no gross physical, motor or behavioral abnormalities. C57BL/6 Cd300lf^-/- mice do not spontaneously develop an overt immune phenotype, nor do they accumulate elevated levels of ACs. However, CD300LF-deficiency leads to ACs phagocytosis defects, and C57BL/6 Cd300lf^-/- are more prone than wildtype mice to develop overt autoimmune symptoms if stressed.
For example, in an ACs+pristane-induced systemic lupus erythematosus (SLE) protocol, C57BL/6 Cd300lf^-/- mice exhibit exacerbated SLE-like disease compared to wildtype controls. When also bred to be FCGR2B-deficient, the resulting C57BL/6 Cd300lf^-/- Fcgr2b^-/- animals develop SLE-like disease that is more severe than C57BL/6 Fcgr2b^-/- animals.
In a dextran sodium sulfate (DSS)-induced colitis protocol, CD300LF-deficiency accelerates the initiation but delays the resolution of intestinal inflammation. Specifically, they exhibit DC-initiated proinflammatory cytokine overproduction and excessive inflammatory responses in the gut - stemming from an unbalanced clearance of ACs, leading to failure to resolve the DSS-induced intestinal inflammation.

In addition, the donating investigator reports that blocking CD300LF function in DCs markedly enhance their ability to phagocytose and process apoptotic tumor cells, and cross-present tumor cell antigens to cytotoxic CD8 T cells (CTL) - all leading to substantial inhibition of tumor growth.

Development

The Cd300f knock-out allele was created for Dr. John E. Coligan (NIAID/NIH) to have exons 2-3 deleted from the CD300 molecule like family member F locus (Cd300lf ; CLM-1) on chromosome 11. First, a targeting vector was used to insert a loxP site upstream of exon 2, and a frt-PGK-neo-pA-SD-frt cassette followed by a second loxP site was inserted downstream of exon 3.

The construct was electroporated into B6.Cg-Thy1^a-derived Bruce 4 embryonic stem (ES) cells. Correctly targeted ES cells were injected into recipient blastocysts, and chimeric animals were bred with C57BL/6J mice for germline transmission.

Offspring were bred with Cre-deleter mice (C57BL/6 genetic background) for germline deletion of exons 2-3 and the neo cassette. Subsequent breeding with C57BL/6J mice removed the cre-expressing allele. The Cd300f^-/- C57BL/6 (also called C57BL/6 Cd300lf^-/-) colony was maintained on a C57BL/6J genetic background as homozygotes. In 2018, C57BL/6 Cd300lf^-/- males with black coat color were sent to The Jackson Laboratory Repository. Upon arrival, sperm was cryopreserved. To establish our live colony, an aliquot of frozen sperm was used to fertilize C57BL/6J oocytes (Stock No. 000664).
Of note, it is not known if the Y chromosome has been fixed to the C57BL/6J background.

Allele

Symbol: Cd300lf^tm1Jco
Name: targeted mutation 1, John E Coligan
MGI accession ID: MGI:5824826
Generation method: Targeted
Attributes: Null/Knockout
Synonyms: Cd300f^-
Marker symbol: Cd300lf
Marker name: CD300 molecule like family member F
Marker synonyms: CD300f; CLM1; CLM-1; DIgR2; F730004D16Rik; IgSF13; IREM1; IREM-1; LMIR3; NKIR; Pigr3; RGD1309733
Chromosome: 11
Strain of origin: B6.Cg-Thy1^a
Molecular note: A loxP site was inserted into intron 1 and a FRT-flanked neomycin resistance gene cassette and a second loxP site into intron 3. The neo cassette and exons 2 and 3 were deleted through subsequent cre-mediated recombination, creating a null allele. Mice carying this allele develop SLE (systemic lupus erythematosus) like phenotypes.