Background: Most arteriovenous malformations (AVMs) are localized and occur sporadically. However, they also can be multifocal in autosomal-dominant disorders, such as hereditary hemorrhagic telangiectasia and capillary malformation (CM)-AVM. Previously, we identified RASA1 mutations in 50% of patients with CM-AVM. Herein we studied non-RASA1 patients to further elucidate the pathogenicity of CMs and AVMs.

Methods: We conducted a genome-wide linkage study on a CM-AVM family. Whole-exome sequencing was also performed on 9 unrelated CM-AVM families. We identified a candidate gene and screened it in a large series of patients. The influence of several missense variants on protein function was also studied in vitro.

Results: We found evidence for linkage in 2 loci. Whole-exome sequencing data unraveled 4 distinct damaging variants in EPHB4 in 5 families that cosegregated with CM-AVM. Overall, screening of EPHB4 detected 47 distinct mutations in 54 index patients: 27 led to a premature stop codon or splice-site alteration, suggesting loss of function. The other 20 are nonsynonymous variants that result in amino acid substitutions. In vitro expression of several mutations confirmed loss of function of EPHB4. The clinical features included multifocal CMs, telangiectasias, and AVMs.

Conclusions: We found EPHB4 mutations in patients with multifocal CMs associated with AVMs. The phenotype, CM-AVM2, mimics RASA1-related CM-AVM1 and also hereditary hemorrhagic telangiectasia. RASA1-encoded p120RASGAP is a direct effector of EPHB4. Our data highlight the pathogenetic importance of this interaction and indicts EPHB4-RAS-ERK signaling pathway as a major cause for AVMs.

中文翻译：

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EPHB4中的种系功能丧失突变会导致第二种形式的毛细血管畸形-动静脉畸形（CM-AVM2）解除RAS-MAPK信号的调控

背景：大多数动静脉畸形（AVM）是局部性的，偶发发生。但是，它们在常染色体显性疾病（如遗传性出血性毛细血管扩张和毛细血管畸形（CM）-AVM）中也可能是多灶性的。以前，我们在50％的CM-AVM患者中发现了RASA1突变。本文中，我们研究了非RASA1患者，以进一步阐明CM和AVM的致病性。

方法：我们对CM-AVM家族进行了全基因组连锁研究。还对9个不相关的CM-AVM系列进行了全外显子组测序。我们鉴定了候选基因，并在大量患者中对其进行了筛选。还在体外研究了几种错义变体对蛋白质功能的影响。

结果：我们发现了在2个基因座中存在连锁的证据。全外显子组测序数据揭示了与CM-AVM共同分离的5个家族中EPHB4的4个不同的破坏性变异。总体而言，对EPHB4的筛查在54例索引患者中检测到47种不同的突变：27例导致过早终止密码子或剪接位点改变，表明功能丧失。其他20个是导致氨基酸取代的非同义变体。几个突变的体外表达证实了EPHB4功能的丧失。临床特征包括多灶性CM，毛细血管扩张和AVM。

结论：我们发现多灶性CM与AVM相关的患者存在EPHB4突变。表型CM-AVM2模仿了RASA1相关的CM-AVM1，也模仿了遗传性出血性毛细血管扩张。RASA1编码的p120RASGAP是EPHB4的直接效应子。我们的数据突出了这种相互作用的致病性的重要性，并指出EPHB4-RAS-ERK信号通路是AVM的主要原因。