TNFAIP3 (A20) and Susceptibility to Systemic Lupus Erythematosus

描述（由申请人提供）：系统性红斑狼疮（SLE）的特征是对大量自身抗原失去免疫耐受性。广泛存在的先天性和适应性免疫功能障碍包括干扰素通路失调、高滴度自身抗体产生、补体功能和免疫复合物清除缺陷。炎症过程导致全身终末器官损伤。尽管几十年的研究，狼疮的潜在遗传基础显然是复杂的和不完全了解。我们的实验室发现TNFAIP3是一种有效的NF-κB信号负调控因子，是SLE风险基因。除SLE外，TNFAIP3区域的遗传变异还与类风湿性关节炎、牛皮癣、克罗恩病、乳糜泻、1型糖尿病、干燥综合征、系统性硬化症和幼年类风湿性关节炎相关，这表明TNFAIP3是自身免疫的主要调节因子。因此，阐明调控TNFAIP3表达和功能的机制可能对人类健康产生广泛影响。通过对多种族SLE队列的精细定位和对TNFAIP3风险单倍型的深度测序，我们在TNFAIP3区域分离出两个与SLE相关的功能变异（rs148314165, rs200820567）。我们发现rs148314165和rs200820567（被称为TT>A变体）存在于一个结合NF-κB和SATB1的增强子元件中，使增强子通过远程DNA环与TNFAIP3启动子相互作用。NF-κB与含有TT>A风险等位基因的增强子结合受损，抑制增强子与TNFAIP3启动子的相互作用，导致A20表达降低。这些结果揭示了rs148314165和rs200820567减弱A20表达的一种新的功能机制，并支持这些变异在自身免疫性疾病易感性中的因果作用。这项建议的主要科学目标将是在这些发现的基础上进一步发展

DESCRIPTION (provided by applicant): Systemic lupus erythematosus (SLE) is characterized by a loss of immunologic tolerance to a multitude of self-antigens. Widespread innate and adaptive immune dysfunction includes interferon pathway dysregulation, high titer autoantibody production, and deficiencies in complement function and immune complex clearance. Inflammatory processes result in systemic end-organ damage. Despite decades of research, the underlying genetic basis of lupus is clearly complex and incompletely understood. Our laboratory identified TNFAIP3, a potent negative regulator of NF-κB signaling, as an SLE risk gene. In addition to SLE, genetic variants in the region of TNFAIP3 are associated rheumatoid arthritis, psoriasis, Crohn's disease, celiac disease, type 1 diabetes, Sjogren's syndrome, systemic sclerosis and juvenile rheumatoid arthritis suggesting that TNFAIP3 is a master regulator of autoimmunity. Therefore, clarifying the mechanisms that regulate TNFAIP3 expression and function are likely to have broad impact on human health. By fine mapping in SLE cohorts of multiple ethnicities and deep sequencing of TNFAIP3 risk haplotypes, we isolated two functional variants (rs148314165, rs200820567) responsible for association with SLE in the region of TNFAIP3. We showed that rs148314165 and rs200820567 (referred to as the TT>A variants) reside in an enhancer element that binds NF-κB and SATB1 enabling the interaction of the enhancer with the TNFAIP3 promoter through long-range DNA looping. Impaired binding of NF-κB to the enhancer harboring the TT>A risk allele, inhibits interaction of the enhancer with the TNFAIP3 promoter resulting in reduced A20 expression. These results reveal a novel functional mechanism by which rs148314165 and rs200820567 attenuate A20 expression and support a causal role for these variants in the predisposition to autoimmune disease. The primary scientific objective of this proposal will be to build upon these discoveries by elucidating mechanisms of TNFAIP3 transcriptional control that influence autoimmune disease risk. In the next funding period we will define the dynamic chromatin state for the TT>A enhancer and other SLE enhancers in primary B cells following stimulation using ChIP-sequencing (Aim 1), characterize the transcription factors and chromatin modifiers that assemble on the TT>A enhancer (Aim 2) and explore the functional effect of a putative novel enhancer 55 kb upstream of the TNFAIP3 promoter (Aim 3). All of these studies will be performed in the context of the SLE risk and nonrisk haplotypes to maximize the clinical relevance of our findings. These studies will serve to clarify new functional mechanisms that regulate TNFAIP3 expression and lay the groundwork for developing of rational therapeutics to restore homeostatic potency of TNFAIP3 in autoimmune disease.