SAP- mice may be useful for studying the role of the SLAM associated protein in cytokine and lymphocyte dysregulation associated with X-linked lymphoproliferative disease.
Pamela L Schwartzberg, National Human Genome Research Institute, National Institutes of Health (NHGRI, NIH)
In SAP- mice, an EGFP and a neomycin (neo) selection cassette were inserted into exon 3 of the X-linked SH2 domain protein 1A (Sh2d1a) gene, abolishing gene expression. The donating investigator reports that the EGFP is non-functional. To assure Sh2d1a was not expressed, a threonine to isoleucine substitution at amino acid 68 (T68I) was introduced in exon 3, upstream of the GFP-PGK-neo cassette. However, the mRNA for this mutant allele is unstable and no protein is made. Sh2d1a encodes a signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) that binds to phosphorylated tyrosine-based motifs in the cytoplasmic tails of the SLAM family surface receptors and links them to downstream signal transduction networks. In the absence of SAP, SLAM family receptors act as strong inhibitory receptors. Mutations in SAP and SAP deficiency have been associated with X-linked lymphoproliferative disease (XLP), a genetic disorder characterized by immune dysregulation and lymphoproliferation caused by fatal responses to Epstein–Barr virus (EBV) infection. XLP leads to symptoms including severe mononucleosis, dysgammaglobulinemia, lymphoproliferation and lymphoma.
SAP- mice exhibit alterations in both CD8+ and CD4+ T cell function, with altered expression of cytokines, severe defects in germinal center formation, defective T follicular helper cell function, and a lack of Natural Killer T cells. Challenge with the infectious agents Toxoplasma Gondii and lymphocyte choriomeningitis virus (LCMV) results in abnormal immune responses, T cell hyperactivation, increased IFN-γ production, decreased B cell function with a lack of long-term antibody responses, and increased morbidity and mortality during chronic infection. Homozygotes are viable and fertile.
Of note, the GFP in these mice is non-functional.
A targeting vector was designed to introduce an enhanced green fluorescent protein (EGFP) and a neomycin (neo) selection cassette into exons 3 of the X-linked SH2 domain protein 1A (Sh2d1a) gene. A threonine to isoleucine substitution at amino acid 68 (T68I) was introduced in exon 3, upstream of the GFP-PGK-neo cassette, to ensure the production of a null allele. The T68I mutation recapitulates mutations found in humans carrying X-linked lymphoproliferative disease (XLP). However, this allele does not generate stable mRNA nor protein. The construct was electroporated into 129S6/SvEvTac-derived TC1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts and the resulting chimeric males were bred to C57BL/6J females. These mice SAP- were backcrossed at least 10 generations to C57BL/6J mice. Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J (Stock No. 000664) for at least one generation to establish the colony.
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 rederived living colony at The Jackson Laboratory Repository. Two of the 43 markers were segregating with 129 on Chromosomes 3 and 16.
|Allele Name||targeted mutation 1, Pamela L Schwartzberg|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Sh2d1a, SH2 domain containing 1A|
|Strain of Origin||129S6/SvEvTac|
|Molecular Note||A splice mutation was introduced to the beginning of exon 3 along with an in-frame GFP-PGK-neo cassette. A threonine to isoleucine substitution at amino acid 68 (T68I), a mutation found in human X-linked lymphoproliferative disease (XLP) that inhibits protein binding, was also incorporated to ensure a null allele. Western blot analysis of thymocyte protein from homozygous mutant animals failed to detect a protein product. Antibodies against GFP also failed to detect a protein product.|
When maintaining a live colony, homozygous mice may be bred together.
When using the B6.129S6-Sh2d1atm1Pls/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #025754 in your Materials and Methods section.
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