Ikaros family genes and lupus susceptibility across ethnically diverse populations

项目摘要 系统性红斑狼疮（SLE）是一种复杂的自身免疫性疾病，有大量的遗传成分。 最近的全基因组关联研究（GWAS）已经确定了SLE相关的基因座，包括IKZF 1和 IKZF 2，分别编码ikaros和helios蛋白。这些蛋白质在调节 免疫细胞的分化在SLE发展中是重要的，调节这些蛋白水平的药物是 用于治疗难治性皮肤狼疮和肾炎，为这些基因的重要性提供了有力的证据 在SLE中。我们最近在亚洲人中进行的基于免疫芯片的相关性研究牢固确立了IKZF 1与SLE的相关性 并检测到额外的独立变体（10-24虽然IKZF 1结果也得到了 在非亚洲人群中，由于SNP覆盖率低，欧洲-GWAS鉴定的IKZF 2（1.2x10-13）不能被 在我们的研究中进行了全面评估。然而，我们的生物信息学数据预测了几种IKZF 1 -2变体， eQTL，再次表明其在表达中的调节作用。尽管有确凿的证据表明存在关联， 因此，IKZF 1 -2风险等位基因在SLE中的功能作用 仍然基本上没有得到解决。由于SLE在非欧洲血统的个体中的患病率高3-5倍， 全面的、基于序列的跨种族绘图（TEM）方法将为双方提供信息 额外的因果变异，并了解不同种族的SLE临床异质性。我们已经成功 在SLE中应用TEM，我们的研究团队拥有必要的专业知识，资源和基础设施， 超越GWAS，加速功能变体的发现和分析。我们成功地确定了 在ITGAM、BLK、IFIH 1和NCF 2中的变体及其功能后果。我们将运用我们的专业知识， 新的变异发现，定位功能变异，以及IKZF 1 -2中功能风险变异的相关性， 与SLE相关的细胞和分子替代物。在目标1中，我们将定位其他SLE易感因素， 通过在四个不同种族中进行全面的跨种族作图， 人群（N> 20，000，来自亚洲、非洲裔美国人、欧洲裔美国人和西班牙裔）。有前途 将通过确证性基因分型验证变异体，尤其是插补和低频变异体。我们将 还使用临床亚表型和自身抗体谱关联遗传和临床异质性。在 目的2，我们将使用最先进的方法来直接识别IKZF 1 -2增强子中的功能变体 重要的是使用一种新的等位基因特异性报告系统，在天然的 染色质背景和相关细胞类型。这使得能够直接实验验证最重要的 人类模型细胞系统中的变异。生成的数据将提供有关SLE疾病机制的答案 受IKZF 1 -2变异体的影响，并了解分子变异体对这种调节的功能。 这一途径可以使现有的治疗靶向这一途径的精确应用，并阐明新的 目标没有严重的不良事件和这些目前的沙利度胺家庭为基础的治疗的局限性。

Project Summary Systemic lupus erythematosus (SLE) is a complex autoimmune disease with a substantial genetic component. Recent genome-wide association studies (GWAS) have identified SLE associated loci, including IKZF1 and IKZF2, encoded for ikaros and helios proteins, respectively. These proteins play important roles in regulation of differentiation of immune cells important in SLE development and drugs which regulate these protein levels are used to treat refractory cutaneous lupus and nephritis making a strong case for the importance of these genes in SLE. Our recent ImmunoChip-based association study in Asians firmly established IKZF1-SLE association and detected additional independent variants (10-24<p<10-8). While IKZF1 results are also well-supported in non-Asian populations, due to poor SNP coverage, European-GWAS identified IKZF2 (1.2x10-13) could not be thoroughly assessed in our study. However, our bioinformatics data predicted several IKZF1-2 variants as eQTLs, again indicating their regulatory roles in expression. Despite solid evidence of association, a gap exists in defining mechanisms with IKZF1-2 variants, hence, the functional effects of IKZF1-2 risk alleles in SLE remains largely unaddressed. Since SLE is 3-5 times more prevalent in individuals of non-European ancestry, a comprehensive, sequence-based trans-ethnic mapping (TEM) approach will be informative to both identify additional causal variants, and understand SLE clinical heterogeneity across ethnicities. We have successfully applied TEM in SLE, and our research team has the expertise, resources and infrastructure necessary to move beyond GWAS and accelerate discovery and analysis of functional variants. We successfully identified causal variants and their functional consequences in ITGAM, BLK, IFIH1 and NCF2. We will apply our expertise in new variant discovery, localizing functional variants, and correlation of functional risk variants in IKZF1-2 on cellular and molecular surrogates associated with SLE. In Aim 1, we will localize additional SLE-predisposing variants from IKZF1-2 by performing comprehensive trans-ethnic mapping across four ethnically diverse populations (N>20,000 from Asian, African-American, European-American, and Hispanic descent). Promising variants, especially imputed and low frequency variants, will be validated by confirmatory genotyping. We will also correlate genetic and clinical heterogeneity using clinical sub-phenotypes and autoantibody profiles. In Aim 2, we will use cutting-edge approaches to directly identify functional variants in the enhancers of IKZF1-2 important for regulating expression using a novel allele-specific reporter system which works in the native chromatin context and in relevant cell types. This enables direct experimental validation of the most important variants in a human model cell system. Data generated will provide answers about SLE disease mechanisms influenced by IKZF1-2 variants, and the understanding of function of molecular variants on regulation of this pathway may enable precision application of existing treatments targeting this pathway and elucidate of new targets without the serious adverse events and limitations of these current thalidomide family-based therapies.