LNPEP基因与汉族人银屑病发病机制相关性研究

Psoriasis is a common immune-mediated polygenic disease that affects the skin, nails and joints. The etiology remains unclear, and it severely affects physical and mental health of patients.The applicant has been endeavoring to the research of the pathogenesis of psoriasis for serveral years. Based on the previous psoriasis GWAS data，we further explore the susceptibility genes with a large sample size（8,339 cases and 12,185 controls）, and identified a new susceptibility gene LNPEP (non-synonymous mutation rs2303138, P=1.87E-12). Some research indicated that LNPEP gene was involved in immune antigen-presenting process through interacting with known psoriasis susceptibility genes MHC-I molecules and ERAP1, activated NF-κB signal pathway and also played a role in the development of diabetes and hypertension that associated with psoriasis. Therefore, It suggests LNPEP gene may play an important role in the pathogenesis of psoriasis. In order to further confirm the association between the LNPEP gene and psoriasis，and investigate the potential role of the gene in the development of psoriasis at the DNA, RNA and cellular level, we plan to perform LNPEP gene sequencing to search for the functional variants and conduct some functional experiment, such as RT-PCR, electrophoresis mobility shift assay (EMSA), luciferase double reporter gene experiments, RNA-mediated interference and so on. Combined with the biological features of previously identified psoriasis genes, it will provide new clues and theoretical basis for promoting the understanding of the pathogenesis of psoriasis.

银屑病是一种常见的免疫相关性多基因病，常累及皮肤、关节和甲。其病因尚未明确，严重危害患者身心健康。申请人一直从事银屑病遗传学研究，基于前期银屑病GWAS数据库，大样本量（8339病例，12185对照）深入发掘，发现银屑病新的易感基因LNPEP（非同义突变rs2303138，P=1.87E-12)。有研究表明该基因与银屑病公认易感基因MHC及ERAP1基因相互作用介导抗原呈递，激活NF-κB信号通路，且与糖尿病、高血压等银屑病伴发疾病的发病密切相关，提示LNPEP基因可能在银屑病发病机制中发挥重要作用。本研究拟通过对LNPEP基因测序搜寻疾病功能性变异，结合RT-PCR、EMSA实验、双报告基因及RNA干扰等功能学实验，在DNA、RNA及细胞水平上验证该基因与银屑病的关联性,提示其在银屑病发病中可能发挥的作用，结合既往发现易感基因的生物学特点，为揭示银屑病发病机制提供新的研究线索和理论依据。

本课题组在前期研究发现LNPEP基因编码变异SNP rs2303138与银屑病相关的基础上，通过基因分型，功能预测，基因表达，通路分析及基因型与表型分析等多角度研究证实LNPEP基因为银屑病易感基因，并提出可能通过肾素-血管紧张素信号通路参与银屑病的发病机制。具体研究如下：1.在7,200例银屑病患者及10,491健康对照人群中进行基因分型，通过大样本量再次证实LNPEP与银屑病存在显著关联性；2.通过运用Polyphen 权威网络服务器检索，发现LNPEP编码区域SNP rs2303138所导致的氨基酸改变 (A763T)，是一种有害变异，极易导致基因生物学功能的破坏；3. 在对GEO 数据库 (Nair et al., 2009)里来自180个皮肤标本（包括58名银屑病患者皮损与非皮损组织和64例正常对照皮肤组织）的表达水平进行检测，发现LNPEP在银屑病患者皮损中的表达不仅与正常对照存在显著性差异(P=1.44*10-6)，与银屑病患者非皮损中的表达也显示显著性差异(P=2.95*10-4)，从组织表达的功能学角度再次证实LNPEP可能参与银屑病发病机制；4.运用KEGG数据库的通路分析发现LNPEP基因涉及血管紧张素信号通路，而该信号通路在心血管疾病及糖尿病发病机制中发挥作用，提示银屑病可能与高血压、糖尿病存在共同的发病通路，而此研究结果恰好也为临床解释银屑病患者易伴发高血压、糖尿病提供了科学依据；5.本研究发现LNPEP基因与早发型银屑病（发病年龄≦40岁）的关联性更强，为银屑病基因型与临床表型的相关性研究提供了初步的遗传学证据。此外，本项目还就银屑病发病机制相关的基因-基因、基因-环境交互作用，功能性编码变异搜寻；非编码变异搜寻及调节基因进行搜寻，以完善银屑病发病机制研究，为最终揭示其发病机制提供更多的前期理论基础和研究思路。