Rare variants (RVs) in the gene encoding the regulatory enzyme complement factor I (; FI) that reduce protein function or levels increase age-related macular degeneration risk. A total of 3357 subjects underwent screening in the SCOPE natural history study for geographic atrophy secondary to age-related macular degeneration, including sequencing and serum FI measurement. Eleven RV genotypes that were challenging to categorize as type I (low serum level) or type II (normal serum level, reduced enzymatic function) were characterized in the context of pure FI protein in C3b and C4b fluid phase cleavage assays and a novel bead-based functional assay (BBFA) of C3b cleavage. Four variants predicted or previously characterized as benign were analyzed by BBFA for comparison. In all, three variants (W51S, C67R, and I370T) resulted in low expression. Furthermore, four variants (P64L, R339Q, G527V, and P528T) were identified as being highly deleterious with IC50s for C3b breakdown >1 log increased versus the WT protein, while two variants (K476E and R474Q) were ∼1 log reduced in function. Meanwhile, six variants (P50A, T203I, K441R, E548Q, P553S, and S570T) had IC50s similar to WT. Odds ratios and BBFA IC50s were positively correlated (r = 0.76, < 0.01), while odds ratios versus combined annotation dependent depletion (CADD) scores were not (r = 0.43, = 0.16). Overall, 15 s were functionally characterized which may aid future patient stratification for complement-targeted therapies. Pure protein analysis remains the gold standard for determining the functional consequence of s.

中文翻译：

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SCOPE 地理萎缩队列中发现的补体因子 I 罕见变异基因型的综合功能特征


编码调节酶补体因子 I (FI) 的基因中的罕见变异 (RV) 会降低蛋白质功能或水平，从而增加年龄相关性黄斑变性的风险。 SCOPE 自然史研究共有 3357 名受试者接受了年龄相关性黄斑变性继发的地理萎缩的筛查，包括测序和血清 FI 测量。在 C3b 和 C4b 液相裂解测定中的纯 FI 蛋白和新型珠子的背景下，对难以归类为 I 型（低血清水平）或 II 型（正常血清水平，酶功能降低）的 11 种 RV 基因型进行了表征。基于 C3b 裂解的功能测定 (BBFA)。 BBFA 对四种预测或先前定性为良性的变异进行了分析以进行比较。总之，三种变体（W51S、C67R 和 I370T）导致低表达。此外，四种变体（P64L、R339Q、G527V 和 P528T）被确定为高度有害，其 C3b 分解的 IC50 与 WT 蛋白相比增加了 >1 个对数级，而两种变体（K476E 和 R474Q）的功能降低了约 1 个对数级。同时，六种变体（P50A、T203I、K441R、E548Q、P553S 和 S570T）的 IC50 与 WT 相似。比值比和 BBFA IC50 呈正相关（r = 0.76，< 0.01），而比值比与组合注释依赖性缺失 (CADD) 评分则不呈正相关（r = 0.43，= 0.16）。总体而言，对 15 s 进行了功能表征，这可能有助于未来针对补体靶向治疗的患者分层。纯蛋白质分析仍然是确定 s 功能结果的金标准。