IgA肾病IgA1糖化缺陷及补体活化异常相关基因的精细定位及功能研究

The pathogenesis of IgAN is incompletely understood yet. Recently it has been found that the disease is correlated with Galactose-Deficient IgA1 and aberrant activation of alternative pathway of complement system. A recent extended whole genome wide association study identified one susceptible locus at 1q31 region which cover the regulator complement activation region (RCA). We have successfully identified 5 independent susceptible loci of Gd-IgA1 and established the methods for testing copy number variation (CNV) of RCA by MLPA and Taqman methods. To carry out fine mapping, we plan to perform exome sequencing to identify candidate genes. Replication study will be conducted in new recruited families as well as sporadic IgAN patients with high Gd-IgA1 levels. We are further about to test the CNV of RCA region in both IgAN patients and healthy controls from an extended cohort, analyze the correlation between RCA CNV and IgAN via association analysis approach and study the biological function of CNV in RCA region through blood, urine and renal tissue complement component testing. The function of candidate variations will be further confirmed by cell model or knock-out mice model. Our study is very important to clarify genetic mechanism of IgAN.

IgA肾病（IgAN）机制不明。最近发现糖化缺陷IgA1（Gd-IgA1）和补体旁路途径异常活化与IgAN密切相关，同时一项全基因组关联分析将IgAN易感基因定位于1q31补体调节区域（RCA）。为探索这两项重要机制的遗传学基础，本课题组已应用QTL连锁分析成功将Gd-IgA1的易感基因定位在5个独立区段，并采用MLPA和Taqman探针方法建立RCA拷贝数变异（CNV）的检测方法。课题组拟采用外显子组测序，对上述易感区段进行精细定位，并在其他高Gd-IgA1家系及散发患者中验证候选基因。同时，拟对大组IgAN患者和正常人进行RCA区域CNV检测，通过关联分析明确候选基因CNV与IgAN之间的相关性，通过对患者血、尿、肾组织补体相关因子的检测阐明其生物学功能。识别出的致病基因通过基因敲除小鼠以及细胞模型验证其功能。本研究对揭示IgAN遗传机制有重要意义。

本课题以我国发病率最高、危害最大的肾小球肾炎，IgA肾病作为研究对象。聚焦IgA1分子糖化障碍和补体活化异常这两项IgAN重要病理生理机制，应用高通量测序、关联分析、拷贝数变异分析、和分子生物学等知识和技术，深入研究其遗传学背景和临床意义，取得系列的研究结果：1）通过拷贝数变异（CNV）研究对CFH因子所在补体调节区域进行精细定位，首次发现CFHR1和CFHR3拷贝数缺失为IgA肾病保护性遗传变异，携带该遗传变异患者间质病变较轻；2）发现补体凝集素途径的启动分子MBL和L-ficolin的遗传变异存在协同作用，加速IgAN患者的肾功能恶化；3）通过关联分析发现G1GALT1和C1GALT1C1的2个遗传位点与糖基化异常IgA1 (Gd-IgA1)相关，可分别解释7%欧洲人和2%亚洲人的血清Gd-IgA1水平变化；4）通过候选位点关联分析，发现HLA-DQ/DR与ST6GAL1常见遗传变异与IgAN预后相关，rs2856717 (HLA-DQ/DR,HR=1.92, 95%CI 1.07-3.43)和rs7634389 (ST6GAL1 c.-182-18109T>C, HR=2.05, 95%CI 1.34-3.12)存在协同效应，同时携带危险等位基因的患者(rs2856717/CT or TT, rs7634389/TT or TC)进展至终点事件的风险增加4倍(HR=4.24, 95%CI 1.81-9.92)；5）Gd-IgA1与基线MAP、UA、血清白蛋白、IgA、IgG水平等具有显著正相关，而与基线eGFR存在显著负相关。采用Cox风险比例模型对Gd-IgA1水平与ESRD的发生进行回归分析，经基线临床参数校正后，与疾病进展风险独立相关(HR=2.45, 95%CI 1.12-5.37)。本课题共发表课题标注论文14篇，其中SCI收录10篇，包括JASN、Kidney International，JMCB等国际高水平杂志，累计影响因子54.2分，中文核心期刊4篇。本研究紧扣临床，所取得一系列原创性成果对推动我国IgAN基础和临床研究具有重要意义，获得2017年教育部科学技术进步奖一等奖（第二完成人）。