Tet1介导DNA羟甲基化对CD4+T细胞活化、分化的调控机制及其在系统性硬化症发病中的作用

At present, the research has confirmed that DNA demethylation contribution to abnormal activation and differentiation of CD4+T cells plays a central role in the pathogenesis of SSc. The molecular basis of DNA demethylation in SSc T cells are still unclear. Rencently, Many studies indicate that the human Tet protein family could catalyse the conversion of 5-methylcytosine(5mC) of DNA to 5-hydroxymethylcytosine (5hmC) raising the possibility that DNA demethylation may be a Tet-mediated process. Because of its demethylation function, DNA hydroxylmethylation play a key role in a variety of biological processes and have attracted much attention. In our previous preliminary study, elevated Tet1 mRNA and protein expression and DNA hydroxylmethylation level were observed in CD4+ T cells from SSc patients. The average level of methylation of the CD11a promoter regions was significantly increased and the percentage of Th17 cells is reduced in SSc CD4+T cells transfected with siRNA-Tet1 as compared with control siRNA–transfected controls. These results suggest that DNA demethylation and activation and differentiation of CD4+T cells may be related to Tet-mediated DNA hydroxylmethylation in SSc patients. On the basis of preliminary experiments, this study is intended to explore Tet-mediated DNA hydroxylmethylation regulatory function of activation and differentiation of CD4+T cells related gene methylation and its molecular mechanism. Furthermore, to reveal the role of Tet-mediated DNA hydroxylmethylation contributing to the development of activation of CD4+T cell, Th17 cell differentiation and autoimmunity by promoting DNA demethylation in SSc CD4 +T cells and its pathogenic role. It will be possible to descover the key aspects and molecular mechanisms of pathological demethylation T cells and autoimmune reactions of SSc patients.These studies provide new insights into the mechanisms causing DNA demethylation in SSc CD4+T cells, and suggest novel approaches for the treatment of SSc and may be a target for more effective SSc treatment.

目前研究已证实DNA低甲基化是引起系统性硬化症（SSc）CD4+T细胞异常活化、分化及发病的重要机制之一，然而其低甲基化机制尚不清楚。DNA羟甲基化是近年来新发现的对DNA甲基化进一步修饰，由Tet蛋白家族氧化所致，可降低甲基化。我们初步研究发现SSc CD4+T细胞Tet1表达及基因组羟甲基化水平增高；抑制SSc中过表达的Tet1，可降低CD11a低甲基化及Th17细胞产生，提示Tet1介导DNA羟甲基化与SSc CD4+T细胞低甲基化及活化、分化有关。本课题拟在上述基础上，检测Tet1表达及染色质局部富集水平；筛选、验证DNA羟甲基化调控的CD4+T细胞活化或分化关键靶基因；探讨Tet1介导DNA羟甲基化对关键靶基因表达、甲基化水平的影响、及在CD4+T细胞活化、向Th17细胞分化、免疫功能及SSc发病中的作用，本课题有助于揭示SSc发病的关键环节和机制，并有望发现SSc治疗的新靶点。