DNA甲基化调控的转录因子EGR1对树突状细胞的功能调控研究

Dendritic cells (DCs) are the most important professional antigen-presenting cells. immature DCs(imDCs) are characterized by high endocytic activity and low T-cell activation potential.when activated by pathogens through pattern recognition receptors (PRRs) such as Toll-like receptor 4 (TLR4) signaling, imDC will become maturation(mDCs) characterized by highly expressing kinds of cytokines and co-stimulatory factors and high ability to present antigens to and activate T cells.How do maturation signal induce this functional switch between immature DC and mature DC? To answer this question from the point of view of epigenetic regulation,we have established DNA methylome and transcriptome of imDCs and mDCs..Take advantage of the database, we have found that a region in the promoter of egr1 undergone upregulated DNA methylation level during DC maturation. This study will reveal that how infection signal induce change of DNA methylation level in the promoter of egr1, and whether high methylated promoter of egr1 repress transcription of egr1. we will also find the targets of EGR1 in DCs and reveal how EGR1 repress the maturation of DC. From this study we will start to know that how infection of pathgen pass signal from plasm membrane to nucleus, and establish special epigenetic regulation network in the level of chromation in mDCs. And we will begin to understand that how DC specific epigenome regulate transcription of key genes that play import roles in induce or repress the maturation of DCs, and establish imDC or mDC specific function. This will also provide new clues to prompt DC vaccine in clinic application for cancer treatment and find more drug targets for DC related immunotherapy, for example DC induced immunologic tolerance in treatment of autoimmune disease.

树突状细胞（DC）为专职抗原提呈细胞，抗原吞噬与加工能力强，但抗原提呈能力弱，当其被感染信号活化后，成熟DC高分泌细胞因子，抗原提呈能力显著增强，可以有效激活T细胞，因此DC是连接天然免疫和适应性免疫的桥梁。基于本课题组建立的人DC分化成熟的全基因组甲基化组和转录组的数据平台，本课题旨在研究DC成熟信号如何完成从胞外经胞浆传递入核，在染色质水平介导表观遗传改变，来调控关键基因的转录，建立起DC特异性的功能状态。通过对DC甲基化谱的分析，发现DC成熟过程中，转录因子EGR1的启动子区存在DNA甲基化变化的区域，针对这一现象，拟研究感染信号如何诱导EGR1启动子区DNA甲基化的改变，DNA甲基化是否参与调控EGR1的转录，EGR1作为转录因子又如何参与调控DC的成熟，从而揭示感染信号如何诱导表观遗传改变来建立成熟DC特有的基因表达模式，从而解释未成熟DC与成熟DC的功能状态转变的机制。

通过树突状细胞（DC)分化成熟的DNA甲基化组，组蛋白H3K4me3和H3K27me3的全基因组分布的组学数据进行整合分析，我们发现了一批DC分化成熟时关键功能分子。首先我们发现DNA甲基化调控的转录因子EGR1，其基因上游在DC成熟时存在差异甲基化区域，通过实验分析发现，DNA甲基化在DC成熟时抑制EGR1的表达，从而促进DC的成熟和对T细胞的活化。同时进一步分析组学数据库发现，Ezh1是树突状细胞成熟过程中最大水平上调的组蛋白甲基转移酶，功能研究发现沉默Ezh1通过直接靶向tollip的近端启动子抑制了Tollip的转录促进TLR信号的活化。进一步分析组学数据发现，炎症诱导的DNA羟甲基化酶Tet2能够在炎症过程中选择性介导IL-6的转录抑制。而Tet2对炎症的抑制作用不依赖于DNA甲基化和羟甲基化，它能够招募Hdac2调节组蛋白的乙酰化修饰水平，达到抑制IL-6 转录的目的。本项目从已建立的组学数据出发，建立了筛选天然免疫关键转录调控分子的研究思路和技术体系，鉴定了一批关键的天然免疫转录调控蛋白，也为免疫和炎症相关疾病提供了靶标。