Functional Analysis of Complement Receptor 2 as a Lupus Susceptibility Gene

描述（由申请人提供）：补体受体2 （CR2/CD21）是NZM2410狼疮小鼠模型Sle 1c狼疮易感性区间中最强的狼疮易感性候选基因，基于其蛋白产物的结构和功能改变。在人类中，CR2位于一个与狼疮易感性相关的同步遗传区间。人类CR2基因5'非翻译区（UTR）的单核苷酸多态性（SNP）减少基因转录并改变转录因子结合。由该SNP加上另外两个CR2 SNP组成的三SNP单倍型与白种人和中国SLE患者及其父母的狼疮易感性相关。该项目概述在本提案将解决的假设，即CR2是人类狼疮易感基因。具体目的是鉴定不同种族群体中与狼疮相关的CR2单倍型块；全面表征5'UTR SNP对基因转录的影响；确定CR2基因中的其他snp是否会改变CR2功能；并证明单个SNP和SNP单倍型对狼疮发病机制的影响。首先，将对非洲裔美国人、高加索人、中国人和西班牙人进行SNP分析，以确定这四个种族群体中单倍型块及其与狼疮的联系和关联。在同时进行的研究中，将对CR2基因编码和调控区域的snp进行功能影响研究。在5'UTR中的SNP的情况下，其功能效应已经被确定，将进行详细的研究来描述它如何改变基因功能。对于调控和编码域的其他snp，在深入研究这些snp可能改变基因功能的机制之前，将进行更一般的评估以确定功能意义。此外，将产生细菌人工染色体（BAG）转基因小鼠，表达个体CR2 SNP以及在小鼠CR2缺陷背景下的CR2 SNP单倍型，以确定特定等位基因是否保护或促进疾病的发展。这些研究将促进我们对CR2作为人类狼疮易感基因的作用的理解，并深入了解其促进疾病发展的机制，从而有可能导致针对CR2的SLE靶向治疗。

DESCRIPTION (provided by applicant): Complement receptor 2 (CR2/CD21) is the strongest candidate gene for lupus susceptibility in the Sle 1c lupus susceptibility interval of the NZM2410 mouse model of lupus, based on structural and functional alterations in its protein products. In humans, CR2 is located in a syntenic genetic interval that is also linked and associated with lupus susceptibility. A single-nucleotide polymorphism (SNP) in the 5' untranslated region (UTR) of the human CR2 gene reduces gene transcription and alters transcription factor binding. A three SNP haplotype consisting of this SNP plus two other CR2 SNPs is associated with lupus susceptibility in Caucasian and Chinese cohorts containing SLE patients and their parents. The project outlined in this proposal will address the hypothesis that CR2 is a lupus susceptibility gene in humans. The specific aims are to identify the CR2 haplotype blocks that are associated with lupus in different ethnic groups; to fully characterize the effects of the 5'UTR SNP on gene transcription; to determine whether additional SNPs in the CR2 gene alter CR2 function; and to demonstrate the effect of individual SNPs and SNP haplotypes on lupus pathogenesis. First, SNP analyses will be performed in cohorts of African-Americans, Caucasians, Chinese, and Hispanics to define haplotype blocks and their linkage and association with lupus in these four ethnic groups. In concurrent studies, the SNPs in the coding and regulatory domains of the CR2 gene will be examined for functional effects. In the case of the SNP in the 5'UTR, for which a functional effect has already been identified, elaborate studies will be performed to characterize how it alters gene function. For the other SNPs in regulatory and coding domains, a more general evaluation to determine functional significance will be performed before delving more deeply into the mechanisms by which these SNPs may alter gene function. In addition, bacterial artificial chromosome (BAG) transgenic mice expressing individual CR2 SNPs as well as CR2 SNP haplotypes on a murine CR2-deficient background will be generated in order to determine whether specific alleles protect from or promote disease development. These studies will advance our understanding of the role of CR2 as a human lupus susceptibility gene and provide insight into the mechanisms by which it contributes to disease development, leading potentially to CR2-targeted therapies for SLE.