Functional Genomics of IL-33 expression and asthma risk

描述（由申请人提供）：哮喘影响全球约3亿人，是基础科学造福临床医学的重要挑战。最近，两项独立的全基因组关联研究数据荟萃分析发现，编码IL-1家族细胞因子IL-33及其受体IL1RL1 （ST2）的基因是哮喘的易感位点。IL-33具有多种功能，包括激活2型先天淋巴样细胞、扩增Th2细胞和增强CD8 T细胞的抗病毒功能。随着将IL-33与哮喘病因联系起来的细胞和分子机制成为人们密切关注的焦点，几个基本问题仍未得到解答。该应用侧重于阐明人类il - 33表达的调控，无论是在转录水平还是在组织水平。虽然已知IL-33在上皮细胞和结构细胞中组成性表达，但我们和其他人最近发现IL-33由小鼠造血细胞产生。我们现在证明了IL33在人肺白细胞中表达，并且过敏原诱导IL33在人CD14+单核细胞中表达。这些发现提示了肺中IL33表达的新范式，并代表了了解该细胞因子在气道Th2炎症中的组织特异性表达的影响的创新机会。利用ENCODE和1000基因组数据库，我们对IL33基因座的调控表观遗传景观进行了计算机分析，并确定了两个高度关注的区域；一个区域具有很强的增强子活性，第二个区域包含两个确定的CTCF结合位点，提示绝缘子活性。我们现在证明，第一个区域可以作为一个增强子，重要的是，这种活性是由一个在非洲血统个体中发现的特异性SNP修饰的。尽管这些公共数据库很有用，但它们未能突出只有在环境刺激诱导基因表达后才变得明显的调控元件。因此，过敏原刺激后原代细胞中IL33表达的调控可能会阐明在静态细胞系中未实现的新调控元件。本研究的核心假设是，调控元件内的非编码遗传变异改变了IL33的时空表达模式，这是IL33位点snp与哮喘风险相关的核心机制。为了验证这一假设，我们提出了以下目标：1)确定受刺激的造血细胞和支气管上皮细胞中IL33基因表达发生的表观遗传变化；2)确定角色

DESCRIPTION (provided by applicant): Asthma affects an estimated 300 million people worldwide and represents an important challenge for basic science to benefit clinical medicine. Recently, two independent meta-analysis of genome wide association studies GWAS data have identified the genes encoding the IL-1¿ family cytokine, IL-33, and its receptor, IL1RL1 (ST2), as susceptibility loci for asthma. A plethora of functions have been attributed to IL-33 including activation of type-2 innate lymphoid cells, expansion of Th2 cells, and augmentation of anti-viral function of CD8 T cells. As the cellular and molecular mechanisms connecting IL-33 to asthma etiology become the focus of intense scrutiny, several basic questions remain unanswered. This application focuses on elucidating the regulation of human IL33 expression, both at the transcriptional level as well as the organismal level. While IL33 is known to be constitutively expressed in epithelial cells and structural cells, we and others have recently found IL-33 produced by murine hematopoietic cells. We now demonstrate that IL33 is expressed in human lung leukocytes and that allergens induce IL33 expression in human CD14+ monocytes. These findings suggest a new paradigm of IL33 expression in the lungs, and represent an innovative opportunity to understand the impact tissue specific expression of this cytokine in airway Th2 inflammation. Using ENCODE and 1000 Genomes databases, we have performed in silico interrogation of the regulatory epigenetic landscape of the IL33 locus and have identified two regions of high interest; one region has strong enhancer activity, and a second region contains two defined CTCF binding sites, suggestive of insulator activity. We now demonstrate that the first region can function as an enhancer, and importantly, this activity is modified by a SNP found specifically in individuals of African ancestry. However useful, these public databases fail to highlight regulatory elements that only become evident after induction of gene expression by environmental stimulation. Thus, regulation of IL33 expression in primary cells after allergen stimulation will likely elucidate novel regulatory elements not realized in static cell lines. The central hypothesis of our study posits that noncoding genetic variants within regulatory elements alter the temporal and spatial expression patterns of IL33, and that this is a central mechanism behind the association of SNPs at the IL33 locus with asthma risk. To test this hypothesis the following aims are proposed: 1) identify the epigenetic changes that occur upon IL33 gene expression in stimulated hematopoietic cells and bronchial epithelial cells.; 2) determine the role the enhancer element(s) play in the regulation of IL33 expression; and 3) determine the role of CTCF in IL33 expression.