The molecular pathogenesis of intracranial aneurysms and subarachnoid hemorrhage

颅内动脉瘤（IA）的患病率在一般人群中约为3%。未破裂的蛛网膜下腔动脉瘤（UIAs）与破裂和随后的动脉瘤性蛛网膜下腔出血（aSAH）的风险相关，其特点是死亡率高。患者家庭成员患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，人们对它知之甚少。尽管几项大型外显子组/基因组全关联研究和外显子组测序（ES）研究分别确定了各种风险位点和候选基因，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，疾病的遗传结构复杂（基因/少基因遗传）或体细胞序列改变导致UIA/aSAH。因此，本研究的主要目标是解决UIA和aSAH的缺失遗传性问题。我们建立了一个包括115人的队列，这些人要么有UIA/aSAH家族史，要么有大量的散发表现。我们对37例不相关的患者（31例散发病例和6例家族病例）和10名受影响的家庭成员（来自家族病例）进行了短读ES。通过使用基于家族的方法（过滤受影响家庭成员共有的变异）和进一步受影响个体的测序，我们在基因EDIL3和TAGLN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序列变异的功能后果，以确定它们在UIA/aSAH发病机制中的相关性。与此同时，我们打算扩展我们的研究：(i)我们将在我们的其他队列中执行ES，以增加可以评估的单个数据集的数量（这对于统计评估至关重要）；此外，将对三个受影响家庭进行全基因组测序。（ii）我们调整我们的生物信息学管道并过滤在我们的非相关患者亚队列中富集的改变基因（基于基因的方法）；为了产生更大的队列，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gene×gene相互作用测试，我们旨在发现可能的遗传和寡基因遗传；为此，我们还与其他财团合作。(v)我们将进行基因产品匹配试验，以确定已确定的序列变异对血管生物学的功能影响。综上所述，我们的研究结果将改善UIA的管理和日常临床环境中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.