Factor H Competitor Generated by Gene Conversion Events Associates with Atypical Hemolytic Uremic Syndrome
Factor H Competitor Generated by Gene Conversion Events Associates with Atypical Hemolytic Uremic Syndrome
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DOI：
10.1681/asn.2017050518
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发表时间：
2018-01-01
影响因子：
13.6
通讯作者：
de Cordoba, Santiago Rodriguez
中科院分区：
文献类型：
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作者：
de Jorge, Elena Goicoechea;Tortajada, Agustin;de Cordoba, Santiago Rodriguez
非典型溶血性尿毒症综合征（aHUS）是一种罕见的由补体致病变异引起的血栓性微血管病，主要影响肾脏微血管系统。使用多重连接探针扩增对我们的 aHUS 队列 (n=513) 进行回顾性遗传分析，发现 9 名不相关的患者在补体因子 H 相关 1 基因 (CFHR1) 中携带遗传异常，该异常源于 CFH 和 CFHR1 基因之间反复发生的基因转换事件。新型 CFHR1 突变体编码具有两个氨基酸取代 L290S 和 A296V 的 FHR-1 蛋白，将 FHR-1 C 末端转换为 H 因子 (FH) 末端。下一代大规模并行 DNA 测序 (NGS) 分析并未检测到这些遗传异常。除了 CFHR1 突变体之外，六名患者还携带先前未表征的 CFH-411T 突变体。在功能分析中，突变的 FHR-1 蛋白强烈竞争 FH 与细胞表面的结合，损害补体调节，而 CFH-411T 多态性缺乏功能后果。 CFHR1 突变携带者在成年期间出现严重的 aHUS；该队列中 57% 的受影响女性出现在产后期。对患者和未受影响携带者的分析表明，由非突变染色体决定的 FH 血浆水平可调节疾病外显率。至关重要的是，在活化内皮 (HMEC-1) 细胞测定中，非突变染色体产生的 FH 血浆水平降低与补体调节受损呈负相关，测量为 C5b-9 沉积。我们的数据促进了对 aHUS 背后遗传复杂性的理解，说明了进行功能分析的重要性，并支持使用补充检测来揭示当前 NGS 分析未揭示的遗传异常。
Atypical hemolytic uremic syndrome (aHUS), a rare form of thrombotic microangiopathy caused by complement pathogenic variants, mainly affects the kidney microvasculature. A retrospective genetic analysis in our aHUS cohort (n=513) using multiple ligation probe amplification uncovered nine unrelated patients carrying a genetic abnormality in the complement factor H related 1 gene (CFHR1) that originates by recurrent gene conversion events between the CFH and CFHR1 genes. The novel CFHR1 mutants encode an FHR-1 protein with two amino acid substitutions, L290S and A296V, converting the FHR-1 C terminus into that of factor H (FH). Next-generation massive-parallel DNA sequencing (NGS) analysis did not detect these genetic abnormalities. In addition to the CFHR1 mutant, six patients carried the previously uncharacterized CFH-411T variant. In functional analyses, the mutant FHR-1 protein strongly competed the binding of FH to cell surfaces, impairing complement regulation, whereas the CFH-411T polymorphism lacked functional consequences. Carriers of the CFHR1 mutation presented with severe aHUS during adulthood; 57% of affected women in this cohort presented during the postpartum period. Analyses in patients and unaffected carriers showed that FH plasma levels determined by the nonmutated chromosome modulate disease penetrance. Crucially, in the activated endothelial (HMEC-1) cell assay, reduced FH plasma levels produced by the nonmutated chromosome correlated inversely with impairment of complement regulation, measured asC5b-9deposition. Our data advance understanding of the genetic complexities underlying aHUS, illustrate the importance of performing functional analysis, and support the use of complementary assays to disclose genetic abnormalities not revealed by current NGS analysis.