The Functional Consequences of the 17q12 Asthma Susceptibility Locus

 描述(由申请人提供)：这项建议的目的是确定导致染色体17q12上的遗传关联与哮喘的哮喘基因。染色体17q12上的常见单倍型是全基因组关联研究中出现的最强、最稳定的可重复性哮喘易感基因。17q12单倍型导致ORMDL3、GSDMB和ZPBP2三个相邻基因的区域染色质重塑。然而，仅从现有的基因数据来看，不可能得出任何确定的结论，这三个人中的哪一个对基因关联负有责任。根据我们的初步数据，我们观察到ORDML3和GSDMB在支气管上皮中都有结构性表达，并且它们的过度表达导致离散的 在哮喘中具有重要意义的分子和细胞后果。相反，我们发现ZPBP2在支气管上皮或其他与哮喘相关的细胞类型中都不表达。因此，我们假设ORMDL3或GSDMB，而不是ZPBP2，会增加哮喘的风险。为了检验这一假设，我们提出了三个具体目标。在具体目标1中，我们将研究我们实验室产生的有条件地在支气管上皮过表达ORMDL3或GSDMB的可诱导转基因小鼠。我们将评估每个基因在已建立的过敏性哮喘小鼠模型中的过度表达的影响，检查其生理、组织学和代谢后果。在具体目标2中，我们将通过实验评估(通过体外基因敲除和过度表达研究)ORMDL3和GSDMB在人类支气管上皮细胞中表达的独立细胞后果，这些细胞来自具有风险和保护性17q12单倍型的纯合个体。在特定的目标3中，我们将从几个方面研究17q12单倍型与鞘脂代谢的关系：(I)我们将测量我们在目标1中研究的小鼠呼吸道和肺组织匀浆中的鞘脂水平，以确定ORMDL3表达的体内影响；(Ii)我们将通过遗传关联来检查17q12调节变异体功能是否导致200名哮喘患者血浆鞘脂水平的变化；以及(Iii)我们将这些血浆鞘脂水平关联起来。 对沙丁胺醇有支气管扩张反应，对乙酰甲胆碱有呼吸道高反应性。通过这些拟议的努力获得的知识将促进我们对这一最重要的哮喘易感基因的理解，并将为开发新的哮喘治疗方法提供必要的基础。

 DESCRIPTION (provided by applicant): The objective of this proposal is to identify the asthma gene that is responsible for the genetic associations on chromosome 17q12 with asthma. A common haplotype on chromosome 17q12 is the strongest, most consistently reproducible asthma-susceptibility locus to emerge from genome-wide association studies. The 17q12 asthma-risk haplotype confers regional chromatin remodeling of three neighboring genes: ORMDL3, GSDMB, and ZPBP2. However, from the available genetic data alone, it is impossible to conclude with any certainty which of these three is responsible for the genetic association. From our preliminary data, we observe that both ORDML3 and GSDMB are constitutively expressed in bronchial epithelium, and that their overexpression results in discrete molecular and cellular consequences of importance in asthma. In contrast, we find that ZPBP2 is not expressed in either bronchial epithelium or other asthma-relevant cell types. We thus hypothesize that ORMDL3 or GSDMB, but not ZPBP2, confers asthma risk. To test this hypothesis, we propose three Specific Aims. In Specific Aim 1, we will study inducible transgenic mice generated in our lab that conditionally over express ORMDL3 or GSDMB in bronchial epithelium. We will assess the effects of each gene's over expression in an established murine model of allergic asthma, examining the physiological, histological, and metabolic consequences. In Specific Aim 2, we will experimentally assess (via in vitro knockdown and over expression studies) the independent cellular consequences of ORMDL3 and GSDMB expression in human bronchial epithelial cells derived from individuals homozygous for the risk and protective 17q12 haplotypes. In Specific Aim 3, we will study the relationship of 17q12 haplotype with sphingolipid metabolism in several ways (i) we will measure sphingolipid levels in the airways & lung homogenates from our murine studies in Aim 1 to determine the in vivo effects of ORMDL3 expression; (ii) we will examine by genetic association whether the functional 17q12 regulatory variant contributes to variations in plasma sphingolipid levels in 200 asthmatics; and (iii) we will correlate these plasma sphingolipid levels with bronchodilator response to albuterol and airways hyperreactivity to methacholine. The knowledge gained through these proposed efforts will advance our understanding of this most important asthma-susceptibility locus, and will provide the requisite foundations for the development of novel asthma therapies.