Interferon Regulatory Factor 5 in Human Lupus Pathogenesis

 描述（由申请人提供）：干扰素调节因子5（IRF 5）是一种转录因子，在Toll样受体（TLR）信号传导后被激活。在全基因组和候选基因关联研究中，IRF 5的遗传变异与系统性红斑狼疮（SLE）易感性强相关。虽然IRF 5与SLE密切相关，但IRF 5易患人类SLE的机制仍不清楚。我们的中心假设是SLE相关的IRF 5变异体促进自身抗体的形成，并改变TLR连接后人类免疫细胞的转录模式，导致SLE的风险。我们先前已经表明，SLE风险单倍型IRF 5与SLE患者和健康自身抗体阳性个体的自身抗体形成相关。HLA基因座与SLE密切相关，由该基因座编码的MHC分子可以指导针对特定自身抗原的免疫应答。我们提出，SLE相关的变体在MHC分子中呈现来自特定核抗原的自身肽，然后IRF 5变体通过增强针对这些抗原的自身反应性B细胞的激活来协同产生自身抗体。在我们的初步数据中，我们支持这一概念的证据表明，在SLE患者自身抗体形成后，IRF 5和HLA之间存在强烈的基因-基因相互作用（OR=3.42）。IRF 5是一种转录因子，似乎风险变体应该通过改变免疫细胞中的转录谱来影响SLE风险。在初步数据中，我们表明IRF 5风险变体导致与人类细胞系中ISRE启动子元件的差异结合。在SLE患者单核细胞中，IRF 5易位到细胞核中大大增加，而在NK和T细胞谱系中观察到的易位增加很少。这些数据支持IRF 5变异在人单核细胞中的重要作用。我们有两个具体目标：目标1：定义人类群体中HLA单倍型和IRF 5遗传变异对自身抗体性状的影响。我们将在IRF 5和HLA位点对1500例SLE患者进行基因分型，以检查IRF 5-HLA基因-基因相互作用对自身抗体性状的影响。此外，我们将研究一个独特的SLE相关自身抗体人群，他们有一系列诊断，包括有进展为SLE风险的无症状人群。目标二：确定SLE患者、自身抗体阳性无症状受试者和健康对照的单核细胞和B细胞中IRF 5 SLE风险变体的转录靶向变化。我们将从IRF 5的风险或保护性单倍型纯合的受试者中纯化来自上述两个谱系的细胞。将用TLR 7或TLR 9配体刺激细胞。将进行ChIP-seq，并比较基因型类别和患者组之间的峰。我们的长期目标是了解人类SLE的致病机制，以便通过特定个体疾病的分子生物学来了解诊断和治疗方法。我们将通过以下预期成果来实现这一目标：1。确定强有力的IRF 5-HLA相互作用，有助于破坏在自身免疫性疾病中观察到的对核抗原的耐受性; 2.定义SLE风险单倍型特征的IRF 5转录靶点，并确定这些转录模式如何与人群（健康、无症状血清阳性和SLE）中不同程度和阶段的自身免疫相关。

 DESCRIPTION (provided by applicant): Interferon regulatory factor 5 (IRF5) is a transcription factor that is activated following Toll-like receptor (TLR) signaling. Genetic variants in IRF5 hav been robustly associated with systemic lupus erythematosus (SLE) susceptibility in both genome-wide and candidate gene association studies. While IRF5 is strongly and consistently associated with SLE, the mechanisms by which IRF5 predisposes to human SLE are still unclear. Our central hypothesis is that SLE-associated variants in IRF5 promote autoantibody formation and alter transcriptional patterns in human immune cells following TLR ligation, resulting in risk of SLE. We have previously shown that SLE-risk haplotypes of IRF5 are associated with autoantibody formation in both SLE patients and healthy autoantibody positive individuals. The HLA locus is strongly associated with SLE, and the MHC molecules encoded by this locus can direct the immune response against particular self-antigens. We propose that SLE-associated variants in MHC molecules present self-peptides derived from particular nuclear antigens, and then IRF5 variants cooperate in autoantibody production by enhancing activation of self-reactive B-cells directed against these antigens. In our preliminary data, we support this concept with evidence for a strong gene-gene interaction between IRF5 and HLA upon autoantibody formation in SLE patients (OR=3.42). IRF5 is a transcription factor, and it seems likely that risk variants should influence SLE risk by altering transcriptional profiles in immune cells. In preliminary data, we show that IRF5 risk variants result in differential binding to ISRE promoter elements in human cell lines. IRF5 translocation to the nucleus was greatly augmented in SLE patient monocytes, while little increased translocation was observed in NK and T cell lineages. These data support an important role for IRF5 variations in human monocytes. We have two Specific Aims: Aim 1: Define gene-gene interactions between HLA haplotypes and IRF5 genetic variants upon autoantibody traits in human populations. We will genotype 1500 SLE patients at the IRF5 and HLA loci to examine IRF5-HLA gene-gene interactions upon autoantibody traits. Additionally, we will study a unique cohort of individuals with SLE-associated autoantibodies who have a range of diagnoses, including asymptomatic people who are at risk of progression to SLE. Aim 2: Determine changes in transcriptional targeting of the IRF5 SLE-risk variants in monocytes and B cells from SLE patients, autoantibody positive asymptomatic subjects, and healthy controls. We will purify cells from the two lineages noted above from subjects homozygous for risk or protective haplotypes of IRF5. Cells will be stimulated with TLR7 or TLR9 ligands. ChIP-seq will be performed, and peaks will be compared between genotype categories and between patient groups. Our long-term goal is to understand the pathogenic mechanisms of human SLE, so that diagnostic and therapeutic approaches can be informed by the molecular biology of disease in a given individual. We will make progress toward this goal via the following expected outcomes: 1. Identify robust IRF5-HLA interactions that contribute to the break in tolerance to nuclear antigens observed in autoimmune disease and 2. Define transcriptional targets of IRF5 that are characteristic of the SLE-risk haplotypes and determine how these transcriptional patterns are associated with varying degrees and stages of autoimmunity in human populations (healthy, asymptomatic seropositive, and SLE).