The molecular pathogenesis of intracranial aneurysms and subarachnoid hemorrhage

在一般人群中，颅内动脉瘤(IA)的患病率约为3%。未破裂的IAS(UIA)与破裂和随后的动脉瘤性蛛网膜下腔出血(ASAH)的风险相关，ASAH的特点是高死亡率。在患者家属中，UIA和ASAH的风险增加。因此，IA/ASAH的遗传基础是显而易见的；然而，人们对其知之甚少。尽管一些大型外显子组/基因组广泛关联研究和外显子组测序(ES)研究分别确定了各种风险基因和候选基因，但有效的疾病基因尚未被描述。这可能是由于测序技术的技术限制、疾病的基因复杂结构(双基因/少基因遗传)或导致UIA/ASAH的体细胞序列改变所致。因此，本研究的主要目的是解决UIA和ASAH的缺失遗传性问题。我们建立了一个由115人组成的队列，这些人要么有UIA/ASAH家族史，要么有大量的零星表现。我们对37例无血缘关系的患者(31例散发性和6例家族性病例)和10名受影响的家庭成员(来自家族性病例)进行了短读ES。通过使用基于家族的方法(筛选受影响的家庭成员共有的变异)和对进一步影响的个体进行测序，我们在EDIL3和TAGLN基因中定义了新的候选风险变异，这两个基因都编码与血管生物学密切相关的蛋白质。现在，我们的目标是表征EDIL3和TAGLN中已识别的序列变体的功能后果，以确定它们在UIA/ASAH发病机制中的相关性。同时，我们打算扩大我们的研究：(I)我们将在队列的其余部分进行ES，以增加可评估的单个数据集的数量(这对统计评估至关重要)；此外，将在三个受影响的家庭中进行全基因组测序。(Ii)我们调整我们的生物信息学管道，筛选在我们的无血缘关系的患者亚群中丰富的改变基因(基于基因的方法)；为了产生更大的群组，我们与其他财团合作。(Iii)我们将分析配对样本ES数据(血液与动脉瘤组织)，以识别体细胞变异。(Iv)通过对ES数据进行彻底的变异关联测试(基因负担/非负担测试)和基因×基因交互作用测试，我们的目标是发现可能的双基因和少基因遗传；我们也为此与其他财团合作。(V)我们将开展基因产物匹配分析，以表征已识别的序列变异对血管生物学的功能影响。综上所述，我们的研究结果应该会改善常规临床环境下的UIA管理和ASAH的风险分层。

The prevalence of intracranial aneurysms (IA) is around 3% in the general population. Unruptured IAs (UIAs) are associated with a risk for rupture and subsequent aneurysmal subarachnoid hemorrhage (aSAH) which is characterized by a high mortality. The risk for UIA and aSAH is increased among patient’s family members. Thus, a genetic basis of IA/aSAH is obvious; however, it is poorly understood. Although several large exome/genome wide association studies and exome sequencing (ES) studies identified various risk loci and candidate genes, respectively, valid disease genes have not been described. This may be due to technical limitations of sequencing technologies, a genetically complex architecture of the disease (digenic/oligogenic inheritance) or somatic sequence alterations causing UIA/aSAH. Therefore, the main goal of this study is to solve the missing hereditability problem for UIA and aSAH. We established a cohort comprising 115 individuals either with a familial history of UIA/aSAH or with a substantial sporadic manifestation. We performed short-read ES in 37 unrelated patients (31 sporadic and 6 familial cases) and 10 affected family members (from the familial cases). By using a family-based approach (filtering for variants shared by affected family members) and sequencing of further affected individuals, we defined novel candidate risk variants in the genes EDIL3 and TAGLN, both of which encoding proteins that are strongly involved in vascular biology. Now, we aim to characterize the functional consequences of the identified sequence variants in EDIL3 and TAGLN in order to determine their relevance in the pathogenesis of UIA/aSAH. In parallel, we intend to expand our study: (i) We are going to perform ES in the rest of our cohort to increase the number of individual datasets that can be evaluated (this is crucial e.g. for statistical evaluations); in addition, genome-wide sequencing is to be carried out in three affected families. (ii) We adapt our bioinformatics pipeline and filter for altered genes which are enriched in our sub-cohort of unrelated patients (gene-based approach); in order to generate larger cohorts, we cooperate with other consortia. (iii) We will analyze paired-sample ES data (blood vs. aneurysmal tissue) to identify somatic variants. (iv) By performing thorough variant association testing (gene burden/non-burden tests) and gene×gene interaction testing with ES data we aim to uncover possible digenic and oligogenic inheritance; we also cooperate with other consortia for this. (v) We will carry out gene product-matched assays to characterize functional impact of identified sequence variants on vascular biology. Taken together, the results from our study should improve the management of UIA and risk stratification for aSAH in a routine clinical setting.