Background and aims EZH2 is an epigenetic regulator that trimethylates lysine 27 of histone 3 (H3K27me3). We have previously suggested that increased EZH2 might be mediating a pro-inflammatory epigenetic reprograming of naïve CD4+ T cells as an early event in lupus flares. Here we examined how overexpression of EZH2 affects the DNA methylome and function in CD4+ T cells.
Methods Naïve CD4+ T cells were isolated from lupus patients and healthy controls. EZH2 was overexpressed, and genome-wide DNA methylation changes were evaluated. Gene expression and miRNAs were assessed by qPCR while protein expression was examined by Western blotting. A cell adhesion assay was used to assess adhesion of T cells to human microvascular endothelial cells (HMVEC).
Results EZH2 expression and H3k27me3 were increased in naïve CD4+ T cells in lupus compared to healthy controls. Both miR-26a and miR-101, which regulate EZH2, were decreased. DNA methylation analysis identified 156 hypomethylated and 168 hypermethylated CpG sites in naïve CD4+ T cells transfected with EZH2. Genes involved in leukocyte adhesion and migration, such as F11R encoding JAM-A (junctional adhesion molecule A), and SELPLG encoding PSGL-1 (P-selectin glycoprotein ligand 1), were hypomethylated. Overexpression of EZH2 resulted in ˜2-fold increased adhesion of CD4+ T cells to endothelial cells. Pre-incubation of EZH2-transfected CD4+ T cells with neutralising antibodies against JAM-A significantly blunted cell adhesion.
Conclusions We uncovered an important role for EZH2 in T cell adhesion. EZH2 overexpression results in hypomethylation of JAM-A, which might increase the migratory ability of T cells and contribute to aggressive T cell extravasation in lupus.
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