Tan Perciliz L, Garrett Melanie E, Willer Jason R, Campochiaro Peter A, Campochiaro Betsy, Zack Donald J, Ashley-Koch Allison E, Katsanis Nicholas
Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States 2Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, United States.
Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, United States.
Invest Ophthalmol Vis Sci. 2017 Mar 1;58(3):1570-1576. doi: 10.1167/iovs.16-20867.
Genome-wide association (GWAS) and sequencing studies for AMD have highlighted the importance of coding variants at loci that encode components of the complement pathway. However, assessing the contribution of such alleles to AMD, especially when they are rare, remains coarse, in part because of the persistent challenge in establishing their functional relevance. Others and we have shown previously that rare alleles in complement factor I (CFI) can be tested functionally using a surrogate in vivo assay of retinal vascularization in zebrafish embryos. Here, we have implemented and scaled these tools to assess the overall contribution of rare alleles in CFI to AMD.
We performed targeted sequencing of CFI in 731 AMD patients, followed by replication in a second patient cohort of 511 older healthy individuals. Systematic functional testing of all alleles and post-hoc statistical analysis of functional variants was also performed.
We discovered 20 rare coding nonsynonymous variants, including the previously reported G119R allele. In vivo testing led to the identification of nine variants that alter CFI; six of which are associated with hypoactive complement factor I (FI). Post-hoc analysis in ethnically matched, population controls showed six of these to be present exclusively in cases.
Taken together, our data argue that multiple rare and ultra-rare alleles in CFI contribute to AMD pathogenesis; they improve the precision of the assessment of the contribution of CFI to AMD; and they offer a rational route to establishing both causality and direction of allele effect for genes associated with this disorder.
年龄相关性黄斑变性（AMD）的全基因组关联（GWAS）和测序研究突出了编码补体途径成分的基因座上编码变异的重要性。然而，评估这些等位基因对AMD的贡献，尤其是当它们罕见时，仍然很粗略，部分原因是在确定其功能相关性方面一直存在挑战。我们和其他人之前已经表明，补体因子I（CFI）中的罕见等位基因可以通过斑马鱼胚胎视网膜血管生成的替代体内试验进行功能测试。在这里，我们应用并扩展了这些工具，以评估CFI中罕见等位基因对AMD的总体贡献。
我们对731例AMD患者的CFI进行了靶向测序，随后在511名老年健康个体的第二个患者队列中进行了验证。还对所有等位基因进行了系统功能测试，并对功能变异进行了事后统计分析。
我们发现了20个罕见的编码非同义变异，包括先前报道的G119R等位基因。体内测试导致鉴定出9个改变CFI的变异；其中6个与补体因子I（FI）活性降低有关。在种族匹配的人群对照中的事后分析表明，其中6个仅在病例中出现。
综上所述，我们的数据表明CFI中的多个罕见和超罕见等位基因促成了AMD的发病机制；它们提高了评估CFI对AMD贡献的准确性；并且它们为确定与该疾病相关基因的等位基因效应的因果关系和方向提供了一条合理的途径。
