A disease-associated PTPN22 variant promotes systemic autoimmunity in murine models
Xuezhi Dai, … , Jane H. Buckner, David J. Rawlings
Xuezhi Dai, … , Jane H. Buckner, David J. Rawlings
Published April 24, 2013
Citation Information: J Clin Invest. 2013;123(5):2024-2036. https://doi.org/10.1172/JCI66963.
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Research Article

A disease-associated PTPN22 variant promotes systemic autoimmunity in murine models

Abstract

Multiple autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, Graves disease, and systemic lupus erythematosus, are associated with an allelic variant of protein tyrosine phosphatase nonreceptor 22 (PTPN22), which encodes the protein LYP. To model the human disease-linked variant LYP-R620W, we generated knockin mice expressing the analogous mutation, R619W, in the murine ortholog PEST domain phosphatase (PEP). In contrast with a previous report, we found that this variant exhibits normal protein stability, but significantly alters lymphocyte function. Aged knockin mice exhibited effector T cell expansion and transitional, germinal center, and age-related B cell expansion as well as the development of autoantibodies and systemic autoimmunity. Further, PEP-R619W affected B cell selection and B lineage–restricted variant expression and was sufficient to promote autoimmunity. Consistent with these features, PEP-R619W lymphocytes were hyperresponsive to antigen-receptor engagement with a distinct profile of tyrosine-phosphorylated substrates. Thus, PEP-R619W uniquely modulates T and B cell homeostasis, leading to a loss in tolerance and autoimmunity.

Authors

Xuezhi Dai, Richard G. James, Tania Habib, Swati Singh, Shaun Jackson, Socheath Khim, Randall T. Moon, Denny Liggitt, Alejandro Wolf-Yadlin, Jane H. Buckner, David J. Rawlings

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Figure 3

PEP-R619W alters T cell homeostasis and TCR signaling.

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PEP-R619W alters T cell homeostasis and TCR signaling. (A) Increased CD4...
(A) Increased CD4+ memory/effector T cells in aged T/C and T/T versus WT littermates. Splenocytes or LN cells were analyzed by FACS for CD4, CD8, CD44, and CD62L expression. Percentages indicate cells within the CD4+ gate (left panels). Absolute numbers of naive and memory/effector CD4+ cells (right panel). Error bars represent SD based on 8 animals/genotype. **P < 0.01. (B) TCR-induced calcium flux in CD4+CD8+ thymocytes (top) and splenic CD4+ T cells (bottom). Cells were stained with indo-1 AM, anti-CD4, and anti-CD8, then stimulated with biotin-conjugated anti-CD3 antibody and cross-linked by streptavidin (arrow). Ca2+ mobilization was determined by flow cytometry. (C and D) Proliferation of naive (C) and memory/effector (D) CD4+ T cells. CD4+CD25–CD62Lhi naive T cells and CD4+CD25–CD62Llo/– memory/effector T cells were isolated from 2-month-old T/C, T/T, and WT littermates. Sorted cells were labeled with CellTrace and stimulated with various doses of anti-CD3 with or without anti-CD28. Cell proliferation was determined by dye dilution. (E) PEP-R619W expression enhances antigen-specific T cell responses in vivo. T/C, T/T, and control mice were immunized with OVA in CFA. Splenocytes were isolated 1 week later and stimulated in vitro with OVA peptide. IL-2 production was measured at 24 hours after stimulation by ELISA. Error bars represent SD based on 3 animals/genotype. *P < 0.05; **P < 0.01. Data shown are representative of 8 (A), 3 (B), 4 (C and D), and 2 (E) independent experiments.