Functional Analysis of Complement Receptor 2 as a Lupus Susceptibility Gene

描述(申请人提供)：补体受体2(CR2/CD21)是狼疮NZM2410小鼠模型中SLE 1c狼疮易感区间中最强的候选基因，基于其蛋白产物的结构和功能变化。在人类中，CR2位于一个共生遗传区间，该区间也与狼疮易感性有关。人CR2基因5‘非翻译区的单核苷酸多态(SNP)降低了基因转录，改变了转录因子的结合。由该SNP和另外两个CR2 SNP组成的三个SNP单倍型与SLE患者及其父母所在的高加索和中国人群中的狼疮易感性相关。该提案中概述的项目将解决CR2是人类狼疮易感基因的假设。其具体目的是确定不同种族中与狼疮相关的CR2单倍型区块；充分表征5‘UTRSNP对基因转录的影响；确定CR2基因中额外的SNPs是否改变CR2功能；以及阐明单个SNPs和SNP单倍型在狼疮发病中的作用。首先，将在非洲裔美国人、高加索人、中国人和拉美裔美国人中进行SNP分析，以确定单倍型块及其与这四个民族中狼疮的联系和联系。在同时进行的研究中，将检查CR2基因编码域和调节域中的SNPs的功能效应。对于5‘非编码区中的SNP，其功能效应已经被确定，将进行详细的研究来表征它如何改变基因功能。对于调节域和编码域的其他SNP，在更深入地研究这些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，还将产生表达单个CR2 SNPs的细菌人工染色体(BAG)转基因小鼠，以及在小鼠CR2缺乏背景下的CR2 SNP单倍型，以确定特定等位基因是保护还是促进疾病发展。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，并提供对其促进疾病发展的机制的洞察，从而有可能导致针对CR2的SLE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.