Investigating the Role of Somatic Mutations in Arteriovenous Malformations

项目摘要 遗传性出血性毛细血管扩张症（HHT）是一种孟德尔疾病，其特征是发展为 多发性局灶性血管畸形（VM），包括大脑中的大型内脏动静脉畸形， 肝和肺;以及粘膜和皮肤组织中的大量毛细血管扩张。这些虚拟机是曲折的 导致动脉和静脉系统之间血液直接高流量分流的血管集合。 HHT相关VM通常导致急性出血、慢性出血、贫血、中风、心脏和肝脏衰竭。 尽管发病率和死亡率与HHT有关，但仍然没有有效的药物治疗， 治疗HHT相关VM;唯一的治疗方法是手术栓塞或切除。这些手术治疗并不 治疗疾病的根源，手术切除后有许多VM再生的病例。此外，本发明还提供了一种方法， 这些治疗是为最大的VM保留的;然而，HHT患者有大量的小VM 其经常出血并且仍然是重要的但不可治疗的医学问题。几十年的研究 专注于了解HHT相关VM的潜在遗传学和血管生物学，然而， 引发VM的分子事件仍然知之甚少。本提案的总体目标是， 对引发血管畸形的分子事件的基本理解。我们早就知道 HHT是由ENG、ACVRL 1或SMAD 4中的常染色体显性功能丧失突变引起的。这些 这些发现使人们相信HHT相关的VM是由突变基因的单倍不足引起的;然而， 这种机制不能解释为什么HHT相关VM是严格的局灶性病变，尽管全身性 突变与单倍不足假说相反，我已经确定HHT相关的VM具有体细胞缺陷。 与致病种系突变相同的基因突变，导致基因的双等位基因功能丧失 产品这些突变与Knudsonian两次击中机制一致，强烈支持功能性突变。 体细胞突变在HHT相关VM发病机制中的作用。本建议的目的是建立在这一发现的基础上 目的是了解这些体细胞突变如何损害血管发育， 畸形这些具体目标的成功实现将填补我们在这方面长期存在的一个关键空白。 HHT生物学的理解，并可能识别新的分子/途径易受治疗干预。 目的1：确定突变细胞类型，并确定畸形中嵌合现象的程度。 目的2：阐明体细胞突变对突变体和野生型细胞的功能影响。 目的3：探讨散发性和遗传性脑VM中体细胞突变的存在。

PROJECT SUMMARY Hereditary Hemorrhagic Telangiectasia (HHT) is a Mendelian disease characterized by the development of multiple focal vascular malformations (VMs) including large visceral arteriovenous malformations in the brain, liver, and lungs; and numerous telangiectasia in mucosal and cutaneous tissue. These VMs are tortuous collections of vessels that result in the direct high-flow shunting of blood between arterial and venous systems. HHT-related VMs often lead to acute hemorrhage, chronic bleeding, anemia, stroke, heart and liver failure. Despite the morbidity and mortality associated with HHT, there remains no effective pharmaceutical therapy to treat HHT-related VMs; the only therapy is surgical embolization or resection. These surgical treatments do not treat the source of the disease and there are numerous cases of VM regrowth after surgical resection. In addition, these treatments are reserved for the largest VMs; however, individuals with HHT have a multitude of small VMs which frequently bleed and remain a significant, yet untreatable, medical problem. Decades of research have focused on understanding the underlying genetics and vascular biology of HHT-related VMs, however the molecular events that initiate VMs remain poorly understood. The overall objective of this proposal is to gain a fundamental understanding of the molecular events that initiate vascular malformation. We have long known that HHT is caused by autosomal dominant loss-of-function mutations in either ENG, ACVRL1, or SMAD4. These findings led to the belief that HHT-related VMs results from haploinsufficiency of the mutated gene; however, this mechanism does not account for why HHT-related VMs are strictly focal lesions despite the systemic mutation. Counter to the haploinsufficiency hypothesis, I have identified that HHT-related VMs harbor a somatic mutation in the same gene as the causal germline mutation resulting in biallelic loss-of-function of the gene product. These mutations are consistent with a Knudsonian two-hit mechanism, strongly supporting a functional role for somatic mutations in the pathogenesis of HHT-related VMs. The aims of this proposal build on this finding with the goal of understanding how these somatic mutations impair vascular development to result in vascular malformation. Successful completion of these specific aims will fill a long-standing critical gap in our understanding of HHT biology and may identify new molecules/pathways susceptible to therapeutic intervention. Aim 1: Identify the mutant cell type and determine the extent of mosaicism in the malformation. Aim 2: Elucidate the functional effects of the somatic mutation on mutant and wild-type cells. Aim 3: Interrogate the presence of somatic mutations in sporadic and hereditary brain VMs.