长链非编码RNA IL21-AS1在系统性红斑狼疮Tfh细胞分化和功能异常中的作用及机制研究

Follicular helper T cells (Tfh) is a newly discovered CD4+ helper T cell subset. The proportion of circulating Tfh cells is increased significantly in the peripheral blood of SLE patients, which specialized to help B cells produce a lot of autoantibodies, playing an important role in the pathogenesis of systemic lupus erythematosus (SLE). Up to now, the molecular mechanism of causing the aberrant Tfh cells response in SLE patients still remains unclear. Our previous experiments found that long non-coding RNA (lncRNA) IL21-AS1 expression level was up-regulated significantly in the induced Tfh cells and CD4+ T cells of SLE patients. In addition, we found that IL-21, a key gene for Tfh cells differentiation and function, is a potential target of IL21-AS1. Therefore, we put forward a hypothesis that the increased IL21-AS1 expression causes the aberrant differentiation and functions of Tfh cells through promoting IL-21 expression, playing an important role in the pathogenesis of SLE. To address the hypothesis, the project will investigate the regulation role and mechanism of IL21-AS1 on the expression of IL-21 gene and the effect of overexpression and silencing of IL21-AS1 on the differentiation and function of Tfh cells and SLE mouse model. This study will further reveal the epigenetic mechanism in the occurrence and development of SLE, and identify novel and effective target for SLE therapy.

滤泡性辅助型T细胞（Tfh）是近年来发现的T淋巴细胞新亚类，在系统性红斑狼疮（SLE）患者外周血中比例明显增加，其通过辅助B细胞产生大量自身抗体在SLE发生发展中起重要的作用。迄今为止，导致SLE患者体内异常Tfh细胞反应的分子机制尚未阐明。我们前期实验发现在体外诱导分化的Tfh细胞和SLE患者外周血CD4+T细胞中长链非编码RNA IL21-AS1表达水平显著升高，Tfh细胞分化和功能关键基因IL-21是其潜在靶基因。为此我们提出：IL21-AS1表达升高通过促进IL-21表达导致SLE患者Tfh细胞分化和功能异常，从而参与SLE发病的全新假说。本项目拟通过探讨IL21-AS1对IL-21表达的调控作用和机制、过表达和沉默IL21-AS1对Tfh细胞分化和功能及SLE小鼠模型的影响来证实这一假说。该研究将有助于深入揭示SLE发病的表观遗传学机制，为寻找SLE治疗新靶点提供理论和实验依据。

系统性红斑狼疮患者体内滤泡辅助性（Tfh）细胞分化比例显著升高，促进B细胞分化及自身抗体生成。然而，导致SLE患者Tfh细胞异常分化的机制仍不清楚。IL-21可以由Tfh细胞分泌并促进Tfh细胞分化，IL21-AS1位于IL21基因的反义链上，已经有很多研究报道反义链lncRNA参与了正义链基因的表达调控，IL21-AS1是否调控IL21表达和Tfh分化还不得而知。我们的实验结果显示IL21-AS1在SLE患者外周血CD4+T细胞和体外诱导的Tfh细胞中表达显著升高，进一步揭示过度表达或干扰IL21-AS1可以促进或抑制Tfh细胞分化。此外，我们构建小鼠同源lncRNA mIl21-AS1过表达小鼠模型（Knock-in mIl21-AS1小鼠），发现mIl21-AS1过表达可促进小鼠体内的体液免疫应答和小鼠狼疮样病理改变。机制方面，我们揭示IL21-AS1通过结合hnRNPU蛋白并招募CBP到IL21启动子区，增加IL21启动子区乙酰化修饰，从而促进IL-21表达和Tfh分化。通过本项目研究，阐明了lncRNA IL21-AS1在SLE发病中的作用及分子机制，为SLE治疗提供了干预新靶点。