Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement
The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.
Altered Fli1 Regulation and Expression in Lupus T Cells and Effects On T Cell Function
Nowling2, Tamara K., Svenson1, John L.
Lupus is a systemic autoimmune disease characterized by increased expression of several inflammatory and transcription factor genes. Mounting evidence indicates strongly that the expression level of the transcription factor gene Fli1 has a significant impact on the pathogenesis of lupus. Currently, little is understood about how Fli1 is regulated in lymphocytes and how its expression affects lymphocyte survival and/or function. To identify mechanisms involved in the transcriptional regulation of Fli1 gene expression in lymphocytes from MRL/lpr lupus mice.
We first isolated splenic T cells from MRL/lpr lupus prone mice and C57BL/6 non-autoimmune prone mice. Cells were stimulated with PMA and Ionomycin. Total RNA was collected and subjected to real-time PCR to assess effects on Fli1 expression. Next, chromatin immunoprecipitation was used to assess the in vivo binding of Ets factors to the Fli1 promoter in MRL/lpr compared to C57BL/6 T cells. Finally, Flow cytometry was used to assess proliferation when Fli1 levels were reduced or increased in T cells of C57BL/6 mice.
Our results demonstrate that Fli1 expression decreases in stimulated T cells from C57BL/6 non-autoimmune prone mice but not MRL/lpr lupus mice. In vivo binding assays demonstrate that the binding of Ets1, Ets2, Fli1 and Elf1 to the endogenous Fli1 promoter in C57BL/6 T cells is altered in primary T cells from MRL/lpr lupus mice. Finally, proliferation of T cells isolated from C57BL/6 with genetically reduced Fli1 activity is increased in response to immune stimuli whereas over-expressing Fli1 in T cells isolated from C57BL/6 results in decreased proliferation.
These results demonstrate that Fli1 expression fails to become down-regulated in MRL/lpr T cells upon activation, likely due aberrant transcriptional regulation. The failure to become down-regulated likely leads to Fli1 over-expression in T cells and these results demonstrate that Fli1 levels impact the proliferation of T cells. Together, our results provide evidence of how changes in regulatory mechanisms may influence expression, cellular function and the pathogenesis of lupus.
To cite this abstract, please use the following information:
Nowling, Tamara K., Svenson, John L.; Altered Fli1 Regulation and Expression in Lupus T Cells and Effects On T Cell Function [abstract]. Arthritis Rheum 2009;60 Suppl 10 :1093