Purpose

To identify genetic variants associated with complement activation, which may help to select age-related macular degeneration (AMD) patients for complement-inhibiting therapies.

Design

Genome-wide association study (GWAS) followed by replication and meta-analysis.

Participants

AMD patients and controls (n = 2245).

Methods

A GWAS on serum C3d-to-C3 ratio was performed in 1548 AMD patients and controls. For replication and meta-analysis, 697 additional individuals were genotyped. A model for complement activation including genetic and non-genetic factors was built, and the variance explained was estimated. Haplotype analysis was performed for 8 SNPs across the CFH/CFHR locus. Association with AMD was performed for the variants and haplotypes found to influence complement activation.

Main Outcome Measures

Normalized C3d/C3 ratio as a measure of systemic complement activation.

Results

Complement activation was associated independently with rs3753396 located in CFH (P_discovery = 1.09 × 10⁻¹⁵; P_meta = 3.66 × 10⁻²¹; β = 0.141; standard error [SE] = 0.015) and rs6685931 located in CFHR4 (P_discovery = 8.18 × 10⁻⁷; P_meta = 6.32 × 10⁻⁸; β = 0.054; SE = 0.010). A model including age, AMD disease status, body mass index, triglycerides, rs3753396, rs6685931, and previously identified SNPs explained 18.7% of the variability in complement activation. Haplotype analysis revealed 3 haplotypes (H1–2 and H6 containing rs6685931 and H3 containing rs3753396) associated with complement activation. Haplotypes H3 and H6 conferred stronger effects on complement activation compared with the single variants (P = 2.53 × 10⁻¹⁴; β = 0.183; SE = 0.024; and P = 4.28 × 10⁻⁴; β = 0.144; SE = 0.041; respectively). Association analyses with AMD revealed that SNP rs6685931 and haplotype H1–2 containing rs6685931 were associated with a risk for AMD development, whereas SNP rs3753396 and haplotypes H3 and H6 were not.

Conclusions

The SNP rs3753396 in CFH and SNP rs6685931 in CFHR4 are associated with systemic complement activation levels. The SNP rs6685931 in CFHR4 and its linked haplotype H1–2 also conferred a risk for AMD development, and therefore could be used to identify AMD patients who would benefit most from complement-inhibiting therapies.

中文翻译：

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全基因组关联研究揭示了与系统补体激活相关的CFH和CFHR4的变异

目的

鉴定与补体激活相关的遗传变异，这可能有助于选择年龄相关性黄斑变性（AMD）患者进行补体抑制疗法。

设计

全基因组关联研究（GWAS），然后进行复制和荟萃分析。

参加者

AMD患者和对照组（n = 2245）。

方法

在1548名AMD患者和对照中进行了血清C3d与C3之比的GWAS分析。为了进行复制和荟萃分析，对另外697个个体进行了基因分型。建立了包括遗传和非遗传因素的补体激活模型，并估计了解释的方差。对CFH / CFHR基因座中的8个SNP进行了单倍型分析。对于发现影响补体激活的变体和单倍型，与AMD进行了关联。

主要观察指标

标准化的C3d / C3比值作为系统补体激活的量度。

结果

补体激活与位于CFH中的rs3753396 （P_发现 = 1.09×10 ^-15 ; P _meta  = 3.66×10 ^-21 ;β= 0.141;标准误差[SE] = 0.015）和位于CFHR4中的rs6685931（P_发现 = 8.18×10 ^-7 ; P _meta  = 6.32×10 ^-8; β= 0.054；SE = 0.010）。包括年龄，AMD疾病状态，体重指数，甘油三酸酯，rs3753396，rs6685931和先前确定的SNP的模型解释了补体激活的18.7％变异性。单倍型分析揭示了与补体激活相关的3个单倍型（H1–2和H6含rs6685931，H3含rs3753396）。与单个变体相比，单倍型H3和H6对补体激活作用更强（P  = 2.53×10 ^-14；β= 0.183； SE = 0.024；P  = 4.28×10 ^-4; β= 0.144；SE = 0.041；分别）。与AMD的关联分析显示，含有rs6685931的SNP rs6685931和单倍型H1-2与AMD发育风险相关，而与SNP rs3753396和单倍型H3和H6无关。

结论

在SNP rs3753396 CFH和SNP rs6685931在CFHR4与全身补体激活水平有关。CFHR4中的SNP rs6685931及其相关的单倍型H1-2也具有AMD发生的风险，因此可用于鉴定从补体抑制疗法中受益最大的AMD患者。