Genetic and Environmental Determinants of Asthma Endophenotypes

 描述(申请人提供)：许多流行病学研究表明，暴露于交通相关的空气污染(TRAP)对儿童和成人的哮喘和相关炎症表型有不利影响。尽管全基因组关联研究已经发现了与哮喘相关的变异，但在识别调节诱捕暴露易感性的基因方面取得的成功有限。我们在小鼠和人类中提出了一种创新的遗传学方法，以确定与TRAP相互作用的新变异，以影响免疫调节内表型和儿童哮喘的风险。具体目标1将确定来自杂交小鼠多样性小组(HMDP)的约150个小鼠品系对柴油废气颗粒物(DEP)的免疫调节反应，DEP是一种与交通相关的模型污染物。小鼠将接受为期两周的鼻内暴露方案，之后将确定肺和脾的细胞免疫调节表型。还将评估这些特征与肺功能之间的关系。我们将使用这些数据进行基因-环境(GxE)GWARD，以确定通过与DEP接触相互作用而影响免疫调节的基因座。在对约40株HMDP菌株的初步研究中，我们观察到免疫调节内表型的~10倍变异性，并在第4和16号染色体上发现了2个与肺Treg频率高度相关的基因座。值得注意的是，以前的GWA已经分别确定了人类1号和3号染色体上的相应基因与儿童哮喘相关的表型有关。这些初步发现与我们的假设一致，即遗传背景调节对TRAP的反应，并支持使用我们提出的整合遗传学方法来识别新的哮喘易感基因。在具体目标2中，我们将使用共线作图来识别通过GxE相互作用影响儿童哮喘相关表型的基因座。这将通过利用4个大型队列中现有的遗传、暴露和临床数据来实现。首先，我们将 使用儿童健康研究(CHS)的Gwas结果来确定人类基因组中与HMDP同源的区域是否与TRAP接触相互作用，从而影响哮喘相关特征。显示GxE相互作用的基因座将在《拉美裔美国人哮喘遗传学》(GALA)1和II以及《非裔美国人哮喘、基因和环境研究》(SAGE)II队列中复制。对于表现出一致的GxE相互作用的基因座，我们将利用这些队列中现有的生物样本来研究FoxP3启动子和FoxP3 mRNA水平的甲基化，作为Treg功能/频率的替代测量。重要的是，在这4个队列中，临床表型和对TRAP暴露的估计高度相似，因此增加了识别和验证真实GxE基因座的可能性。本文提出的综合基因组学方法可以更好地理解基因、环境暴露、免疫调节内表型和哮喘之间的相互关系，这可能对开发新的治疗策略具有重要的临床、流行病学和翻译意义。

 DESCRIPTION (provided by applicant): Numerous epidemiological studies have shown the adverse effects of traffic-related air pollution (TRAP) exposure on asthma and related inflammatory phenotypes in children and adults. Although genome-wide association studies (GWAS) have identified variants associated with asthma, there has been limited success in identifying genes that modulate susceptibility to TRAP exposure. We propose an innovative genetics approach in mice and humans to identify novel variants that interact with TRAP to affect immunoregulatory endophenotypes and risk of childhood asthma. Specific Aim 1 will determine the immunoregulatory responses of ~150 mouse strains from the Hybrid Mouse Diversity Panel (HMDP) to diesel exhaust particles (DEP), a model traffic-related pollutant. Mice will undergo a 2-week intranasal exposure protocol after which cellular immunoregulatory phenotypes will be determined in lung and spleen. The relationship between these traits to lung function will also be assessed. We will use these data to carry out a gene-environment (GxE) GWAS to identify loci that influence immunoregulation through interactions with DEP exposure. In preliminary studies with ~40 HMDP strains, we observed ~10-fold variability in immunoregulatory endophenotypes and identified 2 loci on chromosomes 4 and 16 that exhibited highly suggestive association with pulmonary Treg frequency. Notably, previous GWAS have identified the corresponding loci on human chromosomes 1 and 3, respectively, as being associated with childhood asthma-related phenotypes. These preliminary findings are consistent with our hypothesis that genetic background modulates the response to TRAP and support the use of our proposed integrative genetics approach to identify novel asthma susceptibility loci. In Specific Aim 2, we will use synteny mapping to identify loci that affect asthma-related phenotypes in children through GxE interactions. This will be accomplished by leveraging already existing genetic, exposure, and clinical data in 4 large cohorts. First, we will use GWAS results from the Children's Health Study (CHS) to determine whether regions of the human genome that are syntenic to those identified the HMDP interact with TRAP exposure to affect asthma-related traits. Loci exhibiting GxE interactions will be replicated in the Genetics o Asthma in Latino Americans (GALA) 1 & II and Study of African Americans, Asthma, Genes, & Environments (SAGE) II cohorts. For loci exhibiting consistent GxE interactions, we will leverage already existing biological samples in these cohorts to investigate methylation at the FoxP3 promoter and FoxP3 mRNA levels, as surrogate measures of Treg function/frequency. Importantly, the clinical phenotypes and estimates of TRAP exposure are highly comparable in these 4 cohorts, thus increasing the likelihood of identifying and validating true GxE loci. The integrative genomics approaches proposed herein could lead to a better understanding of the interrelationships between genes, environmental exposures, immunoregulatory endophenotypes, and asthma, which could have important clinical, epidemiological, and translational implications for developing novel treatment strategies.