Background/Purpose: T cells from patients with systemic lupus erythematosus (SLE) express reduced amounts of the critical CD3 zeta signaling chain, and are poor producers of the vital cytokine interleukin (IL)-2. Using a discovery approach (mass spectrometry analysis of proteins “pulled-down” by a CD3 zeta mRNA-defined oligonucleotide), we identified the splicing regulator serine arginine-rich splicing factor 1 (SRSF1). We showed that SRSF1 promotes generation of a full-length CD3 zeta transcript over a short spliced unstable isoform to promote normal expression of CD3 zeta chain in human T cells. Recently we showed that overexpression of SRSF1 into SLE T cells rescues IL-2 production. SRSF1 expression levels are decreased in SLE T cells, more so in patients with worse disease. Although these findings suggest that SRSF1 deficiency is important in the expression of SLE T cell dysfunction, it remains unknown whether SRSF1 contributes to immune-mediated disease. To this end, we generated mice with a T cell-restricted deletion of SRSF1 to evaluate the mechanistic role of SRSF1 in T cell dysfunction and the development of immune-mediated disease in vivo.

Methods: We used the Cre-lox recombination strategy to cross Srsf1 “floxed” B6/129 mice with Lck.Cre (distal promoter) transgenic mice to delete SRSF1 specifically in mature T cells and generate the T cell Srsf1 conditional knockout (Srsf1-cko) mice. Mice were euthanized at 10-16 weeks of age, or aged to >1 year. Central (thymus) and peripheral (spleen, lymph nodes) lymphoid organs were analyzed for immune cell phenotype and function by flow cytometry, enzyme-linked immunosorbent assay (ELISA) and intracellular staining. Serum and urine were collected at monthly intervals to assess autoantibody levels and proteinuria respectively. Lymphoid tissues from aged mice were analyzed for immune cell phenotype and function by flow cytometry. Non-lymphoid (lung, liver, kidney) tissues were fixed, sectioned and stained with hematoxylin and eosin to evaluate histopathology.

Results: The Srsf1-cko mice exhibit T cell lymphopenia, with a striking reduction in the CD8 compartment. The CD4 T cells exhibit increased proportions of activated (CD69hi) cells, and produce increased amounts of IFN-γ and IL-17 upon ex vivo stimulation. The Srsf1-cko mice develop increased levels of anti nuclear autoantibodies (ANA), and exhibit increased proteinuria compared to control mice. Tissue histopathology displays glomerular capillary hyperplasia, glomerular hyperproliferation and interstitial infiltration of mononuclear cells in the kidneys. These results indicate that lack of SRSF1 leads to a reduction of CD8 T cells, aberrantly increased inflammatory cytokine production, autoantibody development and renal pathology. 

Conclusion: Our results reveal that the splicing factor SRSF1 is a novel regulator of T cell homeostasis and function, and its deficiency leads to autoimmunity and kidney damage. Therefore, deficiency of SRSF1 may represent a molecular defect that contributes to the pathogenesis of systemic autoimmune disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/t-cell-restricted-deletion-of-serinearginine-rich-splicing-factor-1-srsf1-in-mice-causes-immune-cell-dysfunction-and-contributes-to-lupus-like-nephritis/