These Mb21d1 (cGAS) knockout mice exhibit increased susceptibility to DNA viruses (murine gamma-herpesvirus 68 and vaccinia virus), and to West Nile virus. These mice may be useful in studies of host response to viral infection or the presence of DNA in the cytosol.
Herbert (Skip) Virgin, Washington University School of Medicine
The Mb21d1 gene encodes for a cytosolic DNA sensor cyclic GMP-AMP synthase that activates the TMEM173/STING pathway for type 1 interferon production. These mice carry a knock-out mutation for the Mb21d1 gene in which exon 2 (encoding the catalytic domain) has been excised. Reduced levels of gene product (mRNA) is detected by qRT–PCR analysis of spleen, lungs, and bone marrow-derived macrophages from homozygous animals. No cGAS protein is detected by immunoblot of skin fibroblasts isolated from knock-out mice. When challenged with DNA viruses, murine gamma-herpesvirus 68 and vaccinia virus, homozygotes exhibit higher viral titers and 100% mortality from vaccinia virus(compare to wildtype control 30% mortality). Homozygotes display increased susceptibility to West Nile virus infection.
To generate this knock-out strain C57BL/6NTac-Mb21d1tm1a(EUCOMM)Hmgu/IcsOrl mice were bred to mice expressing a nuclear localized FLPe recombinase under the control of the CAG, chicken beta-actin promoter and cytomegalovirus enhancer, (C57BL/6-Tg(CAG-FLPe)36Ito/ItoRbrc) to excise the lacZ and neomycin cassettes, leaving exon 2 floxed. The conditional mutant mice were then bred to B6.C-Tg(CMV-cre)1Cgn/J (Stock No. 006054) mice to excise exon 2. The resulting knock-out mice were bred to C57BL/6J mice to remove the Cre recombinase transgene.
Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6J (Stock No. 000664) at least once to establish the colony.
|Allele Name||targeted mutation 1d, Helmholtz Zentrum Muenchen GmbH|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||cGAS; Mb21d1-|
|Gene Symbol and Name||Cgas, cyclic GMP-AMP synthase|
|Strain of Origin||C57BL/6N|
|Molecular Note||The L1L2_Bact_P cassette was inserted at position 78437955 of Chromosome 9 upstream of the critical exon 2 (Build GRCm38). The cassette is composed of an FRT site followed by lacZ sequence and a loxP site. This first loxP site is followed by neomycin resistance gene under the control of the human beta-actin promoter, SV40 polyA, a second FRT site and a second loxP site. A third loxP site is inserted downstream of the targeted exon 2 at position 78437075. The critical exon 2 is thus flanked by loxP sites. Flp-mediated recombination removed the beta-geo cassette and left exon 2 floxed. Cre-mediated recombination removed exon 2. Further information on targeting strategies used for this and other IKMC alleles can be found at http://www.informatics.jax.org/mgihome/nomen/IKMC_schematics.shtml.|
When maintaining a live colony, these mice can be bred as homozygotes.
When using the cGAS KO mouse strain in a publication, please cite the originating article(s) and include JAX stock #026554 in your Materials and Methods section.