Genetic variation influencing brain AVM

评审员#1： 遗传因素在动静脉动静脉畸形形成中的重要性从未被证实. 这一重要的一点现在在第2.3节中得到了仔细的阐述。尽管大多数Avm都是零星的，但也有 确实有证据支持家族成员的存在。最近的一篇综述文章发现了53例AVM 遗传性出血性延髓扩张症(HHT)25个家庭。 关联分析，确定了七个候选区域，其中最强的信号位于染色体6q25 (LOD=1.88；P=0.002)。25由于样本量小，这项研究的动力不足。 散发性动静脉畸形遗传成分的进一步证据来自对同胞复发风险的估计 患病率，评审员1提出的一个重要考虑因素。这一衡量标准，兄弟姐妹，被定义为风险 疾病患者兄弟姐妹的疾病发病率，除以疾病的人口流行率。40 复杂疾病表现出广泛的西贝值。41‘43根据已报道的文献，我们在 第2.3节估计AVM中的Xsibiing，这与疾病的基因贡献一致。 综上所述，至少有少量证据支持动静脉畸形的家族聚集性 表型，尽管缺乏确凿的证据。也许“零星的”一词的使用也加强了 认为不存在任何基因基础的毫无根据的假设。然而，在我们的初步和其他背景下 根据已公布的数据，似乎有理由继续认为基因变异至少会影响 疾病的易感性和临床病程。我们并不假设动静脉畸形病变的“形成”是 是由单个基因座引起的。相反，动静脉畸形是一种复杂的疾病，可能由多种因素引起。连 遗传性出血性延髓扩张症几乎肯定需要一些未知的修饰基因或 AVM表型表达的因素。这种修饰基因的变异可以是可遗传的，例如 是似乎控制血管内皮生长因子诱导的房角遗传的多个遗传位点。 如果...动静脉畸形是零星的，调查人员...需要[正在]寻找体细胞基因组变异。 尽管我们认为有充分的证据表明动静脉动静脉畸形易感性存在遗传成分，但体细胞突变 是一个很好的替代机制的建议。有证据表明中国存在“二次大热”模式 海绵状血管畸形和全身静脉畸形2‘3尽管这一假设令人兴奋，但它也 给Avm带来了重大的后勤问题，因为我们不知道要针对什么基因，尽管ENG和 ALK-1可能是合理的候选者。尽管如此，我们一致认为，从科学上讲， 动静脉畸形的体细胞遗传变异研究。因此，我们进行了体细胞突变的研究 一个探索性的目标，增加了道格·马尔丘克作为联合研究员，他是体细胞突变研究的专家。 候选基因方法论……鉴于其在复杂医学疾病中的过往记录……是不合理的。 评论家在这方面的许多观点都得到了很好的采纳。因此，我们现在已经重塑了方法。 将重点放在全基因组关联(GWAS)上。然而，我们仍然可以利用我们对 考生考虑我们如何跟进我们最初的GWAS分析(见第4.8.1.A节)。《评论家》 提出了复制的重要问题。我们现在强调(第3.3.1节)，我们最近提供了 首次描述了与散发性动静脉畸形相关的一种常见遗传变体：ALK-1的内含子变体，它 与健康对照组相比，动静脉畸形病例中出现的频率更高。81这种关联是 由波恩大学的团队独立复制。德国；78联合的荟萃分析 79‘146我们现在提供了新的初步数据，这种单核苷酸多态 (SNP)与选择性剪接相关(第3.3.1节)，这为功能性剪接奠定了基础 对该变体对基因产物的影响的表征。 然而，预测自发性出血的候选基因变异的数据尚未被复制； 这些结果是作为初步数据提供的。结果事件很少发生的纵向队列 在这一领域活跃的研究小组如此之少的情况下，(出血)的获得要困难得多。我们建议 对于像动静脉畸形这样的罕见疾病，报告与 重要的临床关联，尽管众所周知的假阳性倾向。ALK-1 SNP示例 上面给出的是不同研究小组之间这种协同作用的一个很好的例子。 PHS 398/2590(11/07版)面板171

Reviewer #1: ...importance of genetic factors in formation ofAVMs has never been established... This important point is now carefully addressed in Section 2.3. Although most AVMs are sporadic, there is indeed evidence supporting a familial component. A recent review article identified 53 cases of AVM without Hereditary Hemorrhagic Telangectasia (HHT) in 25 families.39 Further, there has been one linkage and association analysis, which identified seven candidate regions, with the strongest signal at chromosome 6q25 (LOD=1.88; P=0.002).25 This study was unfortunately underpowered due to the small sample size. Further evidence of a genetic component to sporadic AVMs comes from estimation of sibling recurrence risk ratio of disease, an important consideration raised by Reviewer #1. This measure, Sibling, is defined as the risk of disease in siblings of an individual with disease, divided by the population prevalence of the disease.40 Complex diseases display a wide range of Xsibiing values.41'43 Based on the reported literature, we present in Section 2.3 estimates for XSibiing in AVM which are consistent with a genetic contribution to the disease. Taken together, then, there is at least modest evidence supporting familial aggregation for the AVM phenotype, although definitive proof is lacking. Perhaps use of the term "sporadic" also reinforces an unwarranted assumption that no genetic underpinning exists. However, in context of our preliminary and other published data, it seems reasonable to proceed on the notion that genetic variation at least influences the susceptibility and clinical course of the disease. We do not hypothesize that "formation" of AVM lesions is caused by a single genetic locus. Rather, AVM is a complex disease that is likely due to many factors. Even Hereditary Hemorrhagic Telangectasia almost certainly requires some as yet unknown set of modifier genes or factors for the AVM phenotype to be expressed. Variation in such modifier genes may be heritable, e.g., there are multiple genetic loci that appear to control VEGF-induced angle-genesis.60 61 if...AVMs are sporadic, the investigators ... need to [be] searching for somatic genomic variants. Although we believe there is ample evidence for a genetic component in AVM susceptibility, somatic mutation is an excellent suggestion for an alternative mechanism. There is evidence for a "second-hit" model in cavernous malformations6'64 and systemic venous malformations.2'3 As exciting as this hypothesis is, it also presents significant logistical problems for AVMs since we do not know what gene to target, although ENG and ALK-1 might be reasonable candidates. Nonetheless, we agree that it is scientifically important to initiate investigation of somatic genetic variation in AVMs. Therefore, we have made the search for somatic mutations an exploratory aim, adding Doug Marchuk as a Co-investigator, an expert in somatic mutation studies. Candidate gene methodology...given [its] track record ...in complex medical disorders ...is not welljustified. Many of the reviewer's points in this regard are well taken. Accordingly, we have now reshaped the approach to focus on genome-wide association (GWAS). However, we can still leverage our knowledge of plausible candidates in consideration of how we follow up our initial GWAS analyses (see Section 4.8.1.A). The reviewer brought up the important issue of replication. We now emphasize (Section 3.3.1) that we recently provided the first description of a common genetic variant associated with sporadic AVMs: an intronic variant of ALK-1 that was present at a higher frequency in AVM cases compared to healthy controls.81 This association was independently replicated by the group at the University of Bonn. Germany;78 a meta-analysis of combined results was published.79'146 We now provide new preliminary data that this single nucleotide polymorphism (SNP) is associated with alternative splicing (Section 3.3.1), which sets the stage for functional characterization of the effects of this variant on the gene product. Data for candidate genetic variants that predict spontaneous hemorrhage, however, have not been replicated; these results are presented as preliminary data. A longitudinal cohort with an infrequent outcome event (hemorrhage) is far more difficult to obtain with so few research groups active in this area. We would suggest that for a rare disease like AVM, it is not only reasonable but highly constructive to report initial associations of important clinical associations, despite the well-known propensity for false positives. The ALK-1 SNP example given above is a good example of such synergism between different research groups. PHS 398/2590 (Rev.11 /07) Pane 171