Background/Purpose: CD4 T helper 1 (Th1) and Th17 cells producing IFN-γ and IL-17 are aberrantly increased and contribute to inflammatory responses in autoimmune diseases including systemic lupus erythematosus (SLE) and multiple sclerosis. Better understanding of the molecules and mechanisms that control these aberrant responses are important to design better therapeutic strategies. By discovery approaches we previously identified the multifunctional protein serine arginine-rich splicing factor 1 (SRSF1) in human T cells, and showed that it controls genes involved in signaling and cytokine production. We further showed that SRSF1 is low in T cells from SLE patients and associates with active disease. We recently generated T cell restricted Srsf1-conditional knockout (Srsf1-ko) mice. Srsf1-ko mice develop T cell hyperactivity, systemic autoimmunity, and inflammation in peripheral organs. While SRSF1 is an important regulator of gene expression, it is unknown how SRSF1 specifically contributes to CD4 T cell activation/differentiation and resulting inflammation in immune-mediated disease. To this end, we evaluated the role of SRSF1 in the Th1/Th17-dependent experimental autoimmune disease (EAE) and nephrotoxic nephritis (NTN) in vivo.

Methods: T cell conditional Srsf1-heterozygous (het) and homozygous (ko) knockout mice were generated by crossing
Srsf1-flox mice with d.Lck.Cre mice. Peripheral lymphoid organs were analyzed for immune cell phenotype and stimulated ex vivo with PMA/Ionomycin and analyzed by flow cytometry. Naïve CD4 T cells were cultured for 72h with CD3/CD28 and IL-12 for Th1 differentiation. RNA from in vitro generated effector CD4 T cells from WT and Srsf1-ko (n=3 each) mice was subjected to RNA-sequencing. EAE was induced by injecting mice with myelin oligodendrocyte glycoprotein (MOG) peptide with CFA i.p. on day 0, and pertussis toxin i.p. on day 0 and 2. Body weight (BW) and disease scores were recorded daily for 28 days. To induce NTN, mice were preimmunized with sheep IgG (100μg), and 3 days later, nephrotoxic serum (100μl)was administered intravenously. Mice were euthanized on day 24, and tissues collected for analysis. Kidneys were fixed, processed and evaluated blind for histopathology scoring.

Results: CD4 T cells from the Srsf1-ko mice exhibit an increased activated (CD69hi and CD44hi) phenotype and produce increased amounts of IFN-γ and IL-17 upon ex vivo stimulation with PMA/Ionomycin. Increased in vitro Th1 differentiation was observed in CD4 T cells from
Srsf1-ko mice. RNA-seq revealed an overall elevated T cell activation gene signature, increased inflammatory cytokine genes (IL-17A, IL-17F, IFN-γ, IL-4 and IL-21) and increased representation of the Th1/Th17 differentiation pathways in the ko mice. Srsf1-ko mice developed more severe glomerular histopathology scores in NTN and the Srsf1-het mice developed more severe EAE as evidenced by clinical disease scores and BW loss.

Conclusion: SRSF1 is a novel regulator of CD4 T cell activation/differentiation, and its deficiency in T cells leads to autoimmunity and target organ damage. Therefore, deficiency of SRSF1 in T cells may represent a molecular defect that contributes to the pathogenesis of autoimmune disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/serine-arginine-rich-splicing-factor-1-srsf1-restrains-ifn-%ce%b3-and-il-17-inflammatory-cytokine-production-and-its-selective-deficiency-in-t-cells-exacerbates-experimental-autoimmune-encephalomyel/