易感基因应答与感染刺激在Graves病发病中的作用研究

Graves’ disease (GD) is a polygenic disease caused by the interaction of genetic and environmental factors. Current literature shows that bacterial or viral infection is an important environmental factor that induces GD, however the mechanism that triggers the occurrence of GD is not clear. The applicant participated in completing the genome-wide association study of GD as the only one in the world and identified new susceptibility sites. Moreover, the more significant changes in the expression level of GD susceptibility gene ITM2A were identified than individuals with protect genes after stimulation by lipopolysaccharides and interferon-γ. Therefore, we hypothesized that individuals carrying GD susceptibility genes are more likely to prone to GD when mediated by infectious agents. This project intends to verify whether the infection can affect the expression of GD susceptibility genes by detecting the difference in gene expression levels of normal human peripheral blood mononuclear cells stimulated by lipopolysaccharides and interferon-γ at the whole genome level. Further we clarify which susceptibility loci interact with the infection, triggering the occurrence of GD and and its mechanism will be further analyzed. It may provide a new strategy for exploring the interaction between environment and genetics in polygenetic diseases.

弥漫性甲状腺肿伴甲亢（Graves’disease，GD）是一种由遗传易感性和环境因素相互作用所致的多基因疾病。研究表明细菌或病毒感染是诱发GD的重要环境因素，但其通过介导易感基因应答触发GD发生的机制尚不清楚。申请者参与完成了国际上唯一一个GD的全基因组关联研究，识别出了新的易感位点，又首先发现在内毒素、干扰素-γ刺激后，GD易感基因ITM2A的表达水平的变化明显强于携带保护基因的个体。因此，我们设想携带GD易感基因的个体在感染因素介导下，更容易发生GD。本项目拟在全基因组水平上，通过检测正常人外周血单核细胞经内毒素、干扰素-γ刺激后基因表达水平的差异性来验证感染是否可以影响GD易感基因的表达，进一步明确感染是与哪些易感位点相互作用，从而触发GD的发生，并分析其作用机制，为探索多基因病中环境和遗传的相互作用研究提供一种新的策略。

我们利用Fairfax 在单核细胞中发现的影响免疫应答的SNP数据库，与课题组前期的Graves病（GD）易感基因数据进行合并分析，共筛选了711个区段，1,963个SNP群，既和GD高度相关，又影响LPS或IFN刺激前后对基因表达的调控。又将已报道的26个GD易感位点所在的区段与这711个区段进行合并分析，发现有12个区段，GD易感位点及其高度连锁 NP位点，显著调控刺激后的基因表达，其中与刺激后基因表达变化最显著相关的4个GD易感区段为CD40、SLA、RAC2和RNASET2。进一步在中国人外周血单核细胞中的验证同样证实这四个区段的与GD最相关SNP可以调控感染刺激后相应基因的表达。此外，在小鼠腹腔巨噬细胞中的实验发现，RNASET2 基因干扰后，LPS诱导的IL-10表达水平进一步升高，而LPS对TNF-α、IL-6、IFN-β、和IL-1β的表达促进作用不受影响。IL-10是经典的抗炎症细胞因子，对免疫应答有着重要的调节作用。基于以上结果，我们推测RNASET2低表达可能通过促进IL-10对LPS的应答，影响免疫反应，进而影响GD的发生。