THU0008 Hypermethylation of Treg-Specific Demethylated Regions in the Ikaros Transcription Factor Family Members, Helios and EOS, in Rheumatoid Arthritis Tregs

Abstract

BackgroundMembers of the Ikaros family of transcription factors have been implicated in controlling the characteristic phenotype of regulatory T cells (Tregs). Ikaros family zinc finger 4 (IKZF4, Eos) mediates Foxp3-dependent gene silencing and is required to maintain the phenotype of Foxp3-positive Tregs, whereas IKFZ2 (Helios) is involved in the suppression of IL2 gene transcription and upregulation of Foxp3. An important regulation level of tissue-specific gene-expression is DNA methylation. In particular, Treg-specific gene expression is controlled by DNA methylation within characteristic clusters, Treg-specific demethylation regions.ObjectivesTo analyze the DNA methylation status of Treg-specific demethylated regions of Helios and Eos in T cells from patients with rheumatoid arthritis (RA) and to compare the level of methylation to that in T cells from healthy controls.MethodsIn both genes, DNA methylation was assessed by bisulfite sequencing in a CpG island located in an intragenic conserved non-coding sequence (CNS). In addition, a CpG-rich region in exon 6 of the Helios gene was also analyzed.ResultsAll analyzed regions were completely methylated in effector T cells from RA patients and controls. In contrast, considerable degrees of demethylation were detected in the regions of interest in CD25+CD127- T cells, in line with the hypothesis of an important regulatory mechanism facilitating Treg-specific gene expression. Importantly, the methylation rate of the CNS CpG island in the Helios gene was significantly higher in Tregs from RA patients than in those from controls (55% vs. 40%, p<0.05). Similarly, the CpGs within exon 6 of the Helios gene were demethylated to a significantly different level between RA patients and controls (50% vs. 40% methylation, respectively; p<0.05). Finally, in the CNS CpG island of the Eos gene, the methylation level in Tregs from RA patients was also significantly higher as compared to healthy control Tregs (68% vs. 53%, p<0.01).ConclusionsThe data are consistent with the hypothesis of Treg specific expression of Helios and Eos regulated by DNA methylation within Treg-specific demethylation regions. Furthermore, the data suggest that impaired function Tregs in RA might be related to an altered expression of Helios and Eos as a consequence of increased DNA methylation. This mechanism might provide a molecular epigenetic insight into the pathogenesis of autoimmune diseases.Disclosure of InterestNone declared