组蛋白甲基化转移酶EZH2调控Tfh细胞分化的机制研究

Follicular helper CD4 T cells (Tfh cells) play an important role in germinal center B cells (GC B cells)- mediated long-term persisting humoral immune response. Gaining an in-depth investigation of Tfh cells is of vital importance to humoral immunity. Epigenetic regulation plays an important role in various CD4 T cell differentiation, and epigenetic regulator Enhancer of Zeste Homolog2 (EZH2), functioning as a methyltransferase to induce the trimethylation of the histone H3 lysine 27 (H3K27me3), proves to play a critical role in differentiation of various types of CD4 T cells, including Th1, Th2 and regulatory T (Treg) cells. However, whether and how EZH2 regulates Tfh cells differentiation has not been answered. Our previous data showed Tfh cells selectively expressed high levels of EZH2 and ablation of EZH2 resulted in a decreased frequency and total number of Tfh cells in mice during acute viral infection, indicating that epigenetic regulation of EZH2 plays an important role in Tfh cells differentiation. Next, this project will use gene-knockout and overexpression strategy, combined with microarray and ATAC-seq analysis, to explore the regulatory role and molecular mechanism of EZH2 in Tfh cells differentiation, which will provide fundamental basis and valuable insights for future clinical interference in humoral immunity and high-efficiency vaccine development.

滤泡辅助性T细胞（Tfh cells）对生发中心B细胞（GC B）介导的长效体液免疫具有重要作用，深入研究Tfh细胞的分化及作用机制至关重要。多种表观遗传调控作用在CD4 T细胞亚群的分化中起重要作用，其中，组蛋白甲基化转移酶EZH2被证实参与调控包括Th1、Th2和Treg在内的多种CD4 T细胞亚群的分化，但EZH2是否以及如何调控Tfh细胞分化仍未知。本研究前期结果表明，Tfh细胞选择性上调EZH2；条件性敲除EZH2导致病毒感染小鼠模型中Tfh细胞的数量及频率显著降低，以上结果提示：EZH2的表观遗传调控参与Tfh细胞的分化过程。下一步，本课题拟利用基因敲除及过表达技术，结合Microarray与ATAC-seq高通量测序技术，探索EZH2在Tfh细胞分化过程中的调节方式及分子机制，为将来对体液免疫的临床干预以及探索高效的疫苗研发提供新的思路与理论支持。

抗体是机体抗感染免疫的关键，而高效抗体的产生依赖于生发中心(GC）B细胞反应，而Tfh细胞在GC B的形成以及分化中发挥着重要作用，因此深入研究Tfh细胞分化及功能对B细胞介导的体液免疫至关重要。. 我们前期研究发现表观调控因子EZH2介导的H3K27me3表观修饰在LCMV急性病毒感染早期调控Tfh细胞的分化，EZH2缺失导致Tfh细胞分化受到明显抑制。项目获批后，我们继续深入研究，发现在李斯特菌感染模型中，EZH2同样调控Tfh早期分化，且这种调控是内源性；而通过多种动物模型，结合逆转录病毒介导的EZH2基因的调控，以及运用ATAC-seq，Microarray和CHIP-seq等多种高通量手段，揭示了EZH2调控Tfh细胞早期分化的分子机制，即EZH2介导的H3K27me3表观修饰促进Bcl6的表达，从而促进Tfh细胞的分化。.此外，EZH2还通过mTOR信号通路调控其代谢通路，从而调控Tfh细胞高效的免疫反应。并且，mTORC2通过抵抗铁死亡的发生而促进记忆性CD4 T细胞的长效维持。.本课题的研究成果可为开发高效的疫苗以及治疗自身免疫疾病提供新的思路。