Interferon Regulatory Factor 5 in Human Lupus Pathogenesis

 描述(申请人提供)：干扰素调节因子5(IRF5)是一种转录因子，在Toll样受体(TLR)信号转导后被激活。在全基因组和候选基因关联研究中，IRF5的遗传变异与系统性红斑狼疮(SLE)的易感性有很强的相关性。虽然IRF5与SLE密切相关，但IRF5诱发人类SLE的机制仍不清楚。我们的中心假设是IRF5中与SLE相关的变异促进了自身抗体的形成，并在TLR结扎后改变了人类免疫细胞中的转录模式，从而导致了SLE的风险。我们之前已经证明，在SLE患者和自身抗体阳性的健康个体中，IRF5的SLE风险单倍型与自身抗体的形成有关。人类白细胞抗原基因座与系统性红斑狼疮密切相关，该基因座编码的MHC分子可引导机体对特定自身抗原的免疫应答。我们认为，MHC分子中的SLE相关变异体呈现来自特定核抗原的自体多肽，然后IRF5变异体通过增强针对这些抗原的自身反应性B细胞的激活而协同产生自身抗体。在我们的初步数据中，我们支持这一概念，证据表明在SLE患者形成自身抗体时，IRF5和HLA之间存在强烈的基因-基因相互作用(OR=3.42)。IRF5是一种转录因子，似乎风险变异体可能通过改变免疫细胞的转录谱来影响SLE的风险。在初步数据中，我们发现在人类细胞系中，IRF5风险变异导致与ISRE启动子元件的不同结合。在SLE患者单核细胞中，IRF5易位显著增加，而在NK和T细胞系中，易位几乎没有增加。这些数据支持IRF5变异在人类单核细胞中的重要作用。我们有两个特定的目标：目标1：确定人类群体中自身抗体性状与人类白细胞抗原单倍型和IRF5基因变异之间的基因-基因相互作用。我们将对1500名SLE患者进行IRF5和HLA基因分型，以检测IRF5-HLA基因-基因相互作用对自身抗体性状的影响。此外，我们将研究一组独特的患有SLE相关自身抗体的患者，他们有一系列的诊断，包括有进展为SLE风险的无症状患者。目的：检测系统性红斑狼疮患者、自身抗体阳性的无症状患者和健康对照的单核细胞和B细胞中IRF5的转录靶向性变化。我们将从上述两个谱系中提纯IRF5风险或保护性单倍型纯合子受试者的细胞。细胞将被TLR7或TLR9配体刺激。将进行CHIP-SEQ，并比较不同基因型类别和不同患者组之间的峰值。我们的长期目标是了解人类系统性红斑狼疮的发病机制，以便通过特定个体的疾病分子生物学来了解诊断和治疗方法。我们将通过以下预期结果朝着这一目标取得进展：1.确定在自身免疫性疾病中观察到的有助于打破对核抗原耐受性的IRF5-HLA相互作用；2.定义具有SLE风险单倍型特征的IRF5的转录靶点，并确定这些转录模式如何与人类群体中不同程度和不同阶段的自身免疫(健康、无症状血清阳性和SLE)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).