This ICOS- knockout mutation abolishes inducible T cell co-stimulator function. These mutant mice may be useful for studying the ICOS/ICOSL pathway in Th2 and Treg immune responses, humoral immunity (class-switching and memory B cell generation), and inflammatory autoimmune diseases such as asthma (iNKT cell-dependent development airway hyperreactivity (AHR)). As ICOS-ligand expressing vascular endothelial cells facilitate leukocyte recruitment into tissues and metastatic dissemination of tumor cells, these mice may also be useful in studying cancer, metastasis, and antitumor responses.
Arlene H Sharpe, Harvard Medical School
The inducible T cell co-stimulator (ICOS) molecule is a T cell-specific molecule that belongs to the CD28 / CTLA-4 / B7 immunoglobulin superfamily. The activation and function of conventional class II MHC-restricted CD4+ T cells is regulated by T cell receptor (TCR)-signaling and costimulatory molecular pathways (such as the ICOS / ICOS-ligand pathway). ICOS and its ligand (ICOSL / B7h / B7RP-1) have diverse roles in T-cell responses such as mediating autoimmunity, as well as enhancing the development and activity of regulatory T cells. ICOS has a critical role in lung mucosal inflammatory responses mediated, at least in part, by activation and function of invariant NK T cells (iNKT cells). Of note, ICOS-ligand expressing vascular endothelial cells facilitate leukocyte recruitment into tissues and metastatic dissemination of tumor cells.
The phenotype of BALB/c-ICOS-/- mice is described here. Mice homozygous for the ICOS- targeted mutation are viable, fertile and normal in size. This ICOS- targeted mutation has the immunoglobulin (Ig)-V-like exon of the Icos gene replaced by a reverse-oriented neomycin resistance cassette. This mutation abolishes ICOS function; anti-CD3 activated splenocytes from homozygous mice show no ICOS expression or ICOS-ligand binding. Homozygous mice exhibit defective humoral immunity (impaired Ig class-switching and germinal center reactions). Homozygous mice fail to develop allergen-induced airway hyperreactivity (AHR; a cardinal feature of asthma that requires the presence of iNKT cells). BALB/c-ICOS-/- mice have reduced number of peripheral iNKT cells, with iNKT cells producing substantially lower levels of IL-4, IL-5, IFN-γ, IL-13, and IL-10 (but similar levels of IL-2) compared to BALB/c wildtype mice. While ICOS-/- mice on different inbred backgrounds demonstrate enhanced susceptibility to experimental autoimmune encephalomyelitis (EAE), the EAE phenotype of BALBc-ICOS-/- mice is not yet characterized (April 2013).
A targeting vector was designed to replace the immunoglobulin (Ig)-V-like exon 2 of the inducible T cell co-stimulator gene (Icos) with a reverse-oriented neomycin resistance cassette. This construct was electroporated into 129S4/SvJae-derived J1 embryonic stem (ES) cells. The resulting chimeric animals were bred with 129S4/SvJae mice to generate the colony. The mutant mice were then backcrossed with BALB/c inbred mice for at least 11 generations (see SNP results below) prior to sending males to The Jackson Laboratory Repository in 2013. Upon arrival, males were used to cryopreserve sperm. To establish the living mouse colony, an aliquot of the frozen sperm was used to fertilize BALB/cByJ oocytes (Stock No. 001026).
In 2013, a SNP (single nucleotide polymorphism) panel analysis, with 26 markers covering all 19 chromosomes and the X chromosome, as well as 4 markers that distinguish between the BALB/cJ and BALB/cByJ substrains, was performed on the first generation rederived living colony at The Jackson Laboratory Repository. While 24 of 26 markers throughout the genome suggested a BALB/c genetic background, the two markers nearest Icos were 129 allele-type (like the ES cells used). In addition, 3 of 4 markers that determine BALB/cJ from BALB/cByJ were found to be heterozygous (the marker at the proximal end of chromosome 7 was homozygous for BALB/cByJ allele-type). These data confirm the mice sent to The Jackson Laboratory Repository were on a BALB/c genetic background.
|Allele Name||targeted mutation 1, Arlene H Sharpe|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Icos, inducible T cell co-stimulator|
|Strain of Origin||129S4/SvJae|
|Molecular Note||Exon 2, which contains an immunoglobulin -V-like sequence, was replaced with a neomycin resistance gene. Absence of gene product was demonstrated immunologically.|
When maintaining a live colony, homozygous mice may be bred together.
When using the C.129S4-Icostm1Shr/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #017605 in your Materials and Methods section.