Systemic complement and age-related macular degeneration.

描述（由申请人提供）：视网膜相关性黄斑变性（AMD）是发达国家老年人视力丧失的主要原因。补体因子H（CFH）和CFH相关蛋白（CFHR 1至CFHR 5）与AMD的发展有关。这些相关蛋白质编码在人类染色体1 q31中的补体激活调节（RCA）基因簇中。CFH的两种主要蛋白变体Y 402 H和I62 V与AMD的风险密切相关。CFHR 3/CFHR 1的纯合缺失在AMD中具有保护作用。Y 402 H和I62 V风险变体具有损害抗炎和调节CFH功能的结构变化。CFHR蛋白在几个结合位点与CFH竞争。虽然RCA基因簇中编码的补体蛋白在AMD发病机制中的遗传研究中有很强的关联，但知识的主要空白是CFH和五种CFHR蛋白的系统水平如何与AMD相关。这项多中心的合作研究将使用流行病学方法，从遗传水平到循环蛋白及其变体和亚型的表达来推进知识。我们已经开发了一种新的多路复用多反应监测（MRM）分析的基础上，质谱法，可以测量所有四种变体的CFH的血浆水平。MRM克服了免疫测定法在检测高度相似的同源物和序列变体（如在CFH和CFHR蛋白中发现的同源物和序列变体）方面的局限性。我们的初步研究表明，系统性CFH风险变异与AMD相关。在该提案的支持下，我们建议进一步开发MRM测定法，以包括所有五种CFHR蛋白及其亚型。我们假设：（1）AMD的风险与CFH变体Y 402 H和I62 V的血浆浓度以及补体因子H相关蛋白CFHR 1至CFHR 5的血浆浓度相关，（2）常见的单核苷酸多态性（SNP）和其他因素与CFH变体和CFHR蛋白的血浆水平的变化相关。具体目标是：（1）表征血浆CFH Y 402 H和I62 V变体水平与AMD风险之间的关系，（2）开发用于测量血浆CFHR 1至CFHR 5的MRM测定，（3）表征血浆CFHR 1至CFHR 5水平与AMD风险之间的关系，和（4）通过全基因组关联研究（GWAS）鉴定与CFH变体和CFHR 1至CFHR 5的血浆水平相关的SNP和其它因素。为了实现这些目标，我们将在年龄，基因/环境易感性-雷克雅未克（AGES-Reykjavik）研究中的4，907名参与者中检查基线时血浆CFH Y 402，H402，I62和V62变体以及CFHR 1与CFHR 5的关系。GWAS将鉴定与各自CFH和CFHR蛋白水平相关的SNP。AGES-Reykjavik研究是一项以人群为基础的流行病学研究，旨在确定导致老年人疾病的因素。这项研究将评估有希望的候选生物标志物，并帮助确定系统性CFH和CFHR蛋白是否在AMD中发挥作用，并代表风险分层和/或治疗干预的潜在途径。

DESCRIPTION (provided by applicant): Age-related macular degeneration (AMD) is the leading cause of visual loss among older adults in developed countries. Complement factor H (CFH) and CFH-related proteins (CFHR1 to CFHR5) are implicated in the development of AMD. These related proteins are encoded in the Regulation of Complement Activation (RCA) gene cluster in human chromosome 1q31. Two major protein variants of CFH, Y402H and I62V, are strongly associated with risk of AMD. A homozygous deletion in CFHR3/CFHR1 is protective in AMD. The Y402H and I62V risk variants have structural changes that impair anti-inflammatory and regulatory CFH functions. CFHR proteins compete with CFH at several binding sites. Although complement proteins encoded in the RCA gene cluster are strongly implicated by genetic studies in the pathogenesis of AMD, a major gap in knowledge is how systemic levels of CFH and the five CFHR proteins are related to AMD. This multi-center, collaborative study will use an epidemiological approach to advance knowledge from the genetic level to the expression of circulating proteins and their variants and isoforms. We have developed a novel multiplexed multiple reaction monitoring (MRM) assay based upon mass spectrometry that can measure the plasma levels of all four variants of CFH. MRM overcomes the limitations of immunoassays in detection of highly similar homologues and sequence variants such as that found in CFH and CFHR proteins. Our pilot studies suggest that systemic CFH risk variants are associated with AMD. We propose, under the support of this proposal, to further develop the MRM assay to include all five CFHR proteins and their isoforms. We hypothesize: (1) risk of AMD is associated with plasma concentrations of CFH variants Y402H and I62V and plasma concentrations of complement factor H-related proteins CFHR1 to CFHR5, (2) common single nucleotide polymorphisms (SNPs) and other factors are associated with variations in plasma levels of both CFH variants and CFHR proteins. The specific aims are to: (1) characterize the relationship between plasma CFH Y402H and I62V variant levels and risk of AMD, (2) develop MRM assays for measuring plasma CFHR1 to CFHR5, (3) characterize the relationship between plasma CFHR1 to CFHR5 levels and risk of AMD, and (4) identify SNPs and other factors associated with plasma levels of CFH variants and CFHR1 to CFHR5 through a genome-wide association study (GWAS). To address these aims, we will examine the relationship of plasma CFH Y402, H402, I62, and V62 variants and CFHR1 to CFHR5 at baseline in 4,907 participants in the Age, Gene/Environment Susceptibility-Reykjavik (AGES-Reykjavik) Study with prevalent and incident AMD. A GWAS will identify SNPs associated with respective CFH and CFHR protein levels. The AGES-Reykjavik Study is a population-based epidemiological study aimed at identifying factors that contribute to disease in older adults. This study will evaluate promising candidate biomarkers and help to determine whether systemic CFH and CFHR proteins play a role in AMD and represent a potential pathway for risk stratification and/or therapeutic intervention.