TNFSF15在麻风、克罗恩病和原发性胆汁性肝硬化中的功能研究

Leprosy is an infectious disease caused by Mycobacterium leprae while both Crohn's disease (CD) and PBC (Primary biliary cirrhosis) are immune-related inflammatory diseases. Studies have confirmed that the Pathogenesis of the three diseases were associated with the host genetic predisposition, and TNFSF15 is shared susceptibility gene among leprosy, CD and PBC. More importantly, Genome-wide Scan data demonstrate that the effects of the three Tag SNPs of TNFSF15 (rs4366152 in leprosy，rs6478108 in CD，rs4979462 in PBC)are opposite between leprosy and CD, PBC. Moreover, the expression level of TNFSF15 is increased in CD and PBC, but decreased in leprosy, this suggest that TNFSF15 may show opposite effect between infectious disease and inflammatory disease, and the elucidation of pathogenesis of the three diseases are important. We are planing to perform validation analysis in leprosy cases and controls from China, CD cases and controls from Korea and PBC cases and controls from Japan respectively under the help of Katsushi Tokunaga from the University of Tokyo. Then,we will carry out statistical analysis of genotyping data of the validation samples and confirm the effect in these three diseases. Furthermore, we will collect tissues from leprosy, CD and PBC cases, perform functional analysis of TNFSF15 by RT-PCR, immunohistochemistry, flow cytometry and so on. This study will be helpful for the elucidation of the link among the pathogenesis of the infectious and inflammatory diseases.

麻风是由麻风分枝杆菌感染所致的一种传染病，而克罗恩病（CD）和原发性胆汁性肝硬化（PBC）均为与免疫密切相关的炎症性疾病。研究已经证实三者的发生均与宿主的遗传素质相关，其中TNFSF15为三者共有易感基因位点。该基因在以上三种疾病中的SNPs位点在麻风与在CD和PBC中效应相反，后续研究又发现其在麻风中低表达，而在CD和PBC中却高表达，提示该基因在感染性疾病与炎症性疾病中发病机制不同，了解其具体机制对阐述三种疾病的发病机理至关重要。因此课题组拟在日本Katsushi Tokunaga教授协助下，将前期发现的SNPs在三种疾病中进行验证，获得分型数据，以确定TNFSF15基因在三种疾病中的效应。同时利用这些疾病的组织标本，采用模式动物实验等功能研究对TNFSF15在疾病发病免疫应答中的作用进行探索，为阐述感染性疾病与炎症性疾病发病间的内在关联奠定基础。

基因组9q32区域既往报道与多种疾病相关联，且存在相同或相反的效应，如原发性胆汁性硬化、克罗恩病和麻风等。但是，目前仍不清楚该区域内哪个基因的哪个变异起作用，起何种作用,而其中的TNFSF15基因则是研究的热点，在本课题组既往麻风研究中也发挥了重要作用。本项目通过三阶段精细定位研究对9q32区域进行分析，样本来源于三个大规模的疾病队列，中国的麻风（9,619 病例 和 12,896对照）,韩国的克罗恩病(1,576 病例和 3,013对照) 以及 日本的原发性胆汁性肝硬化 (1,594 病例和1,529对照)。方法为全基因组关联分析、基因型推算、大规模基因分型及变异注释等。在麻风和克罗恩病中发现了两个独立的关联信号，且在不同疾病中效应相反；在原发性胆汁性肝硬化发现了一个独立的关联信号。显著的eQTL效应提示该关联信号可以对TNFSF15的表达具有调控作用，且具有细胞/组织特异性。TNFSF15基因对原发性胆汁性肝硬化、克罗恩病和麻风均具有作用，且调控其作用的变异不同且具有细胞/组织特异性。