THU0004 Camp responsive element modulator (CREM) alpha contributes to decreased NOTCH-1 expression in T cells from patients with systemic lupus erythematosus (SLE)
Authors: T. Rauen, A. Grammatikos, C.M. Hedrich, V.C. Kyttaris, K. Tenbrock, U. Raffetseder, J. Floege, G.C. Tsokos
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Notch signaling constitutes an evolutionarily conserved pathway that transduces signals between neighbouring cells and determines major decisions in cell proliferation, survival and differentiation. Notch signaling has been shown to play a pivotal role in T cell lineage specifications. T lymphocytes from patients with systemic lupus erythematosus (SLE) display a severely altered phenotype with several molecular and functional aberrations including defective capacities to up-regulate Notch-1 receptor expression upon T cell receptor activation (1-3). <h3>Objectives</h3> The goal of the present study was to analyze basal Notch-1 expression levels and differential mechanisms of Notch-1 gene transcription in T cells from SLE patients and healthy controls. <h3>Methods</h3> We analyzed basal Notch-1 mRNA expression using real-time quantitative PCR in total T cells from a cohort of 61 SLE patients (diagnosed according to ACR criteria) with 32 of them classified as active patients (SLEDAI ≥4) and 24 healthy control individuals. Subpopulations of these individuals were analyzed for Notch-1 protein expression in various T cell subsets by FACS surface staining (e.g. CD4<sup>+</sup>, CD8<sup>+</sup>, double negative T cells). Chromatin immunoprecipitation, CpG-DNA methyl-immunoprecipitation assays, transfection studies and reporter assays were performed to analyze mechanisms of Notch-1 regulation. <h3>Results</h3> We demonstrate that also basal Notch-1 expression is decreased in T cells from active SLE patients at the messenger and protein level in various T cell subpopulations. <i>Notch1</i> transcript numbers inversely correlate to disease activity in SLE patients. We provide evidence that both, enhanced histone H3 and CpG-DNA methylation of the human <i>Notch1</i> promoter contribute to decreased Notch-1 expression in SLE T cells. Previous data from our group identified cAMP responsive element modulator (CREM)α, which is up-regulated in SLE T cells, as a key regulator of the epigenetic conformation and gene transcription, e.g. that of <i>IL2</i> and <i>IL17</i> genes. In this study, we observed increased CREMα binding to the <i>Notch1</i> promoter which results in a significantly repressed <i>Notch1</i> promoter activity and gene transcription. <h3>Conclusions</h3> Our data suggest a critical role for Notch-1 in SLE immunopathogenesis and, for the first time, we present molecular mechanisms that mediate dysregulated Notch-1 expression in SLE T cells. <h3>References</h3> Amsen D et al. 2009. The different faces of Notch in T-helper-cell differentiation. Nat Rev Immunol 9:116-124. Tsokos GC. 2011. Systemic lupus erythematosus. The New England Journal of Medicine 365:2110-2121. Sodsai P et al. 2008. Defects in Notch1 upregulation upon activation of T Cells from patients with systemic lupus erythematosus are related to lupus disease activity. Lupus 17:645-653. <h3>Disclosure of Interest</h3> None Declared