Molecular mechanisms underlying Arteriovenous Malformations associated with HHT

项目总结 遗传性出血性毛细血管扩张症是一种常染色体显性遗传病，影响男性 和来自所有种族和民族的女性，每5000人中有1人。HHT的特征是 动脉和静脉之间不适当的连接，称为动静脉畸形(Avms)。这些 脆弱的连接可能会出血和破裂，导致贫血、动脉瘤、中风甚至死亡。值得注意的是， 目前还没有有效治疗HHT患者动静脉曲张的药物，尽管先前发现了 与HHT相关的信号通路缺陷。HHT的遗传原因与转化有关 生长因子-β(转化生长因子β)信号通路，大约85%的患者表现出 Endoglin(Eng)或激活素受体样激酶1(Acvrl1)共受体。约4%的人在 下游转录因子Smad相关蛋白4(Smad4)。尽管多年来HHT的研究主要是 集中在英语和Acvrl1上，我们的知识中仍然存在两个关键差距-全面理解 HHT血管系统的细胞形态和生物学缺陷及其下游基因的鉴定 它们对血管缺陷负有机械上的责任。我们已经创造了一种新的小鼠模型 AVM/HHT通过基因消融血管中的Smad4有效复制细胞 与羟色胺相关的生物缺陷。使用我们的模型，我们已经开始了详细的分子和细胞 体内HHT血管的特征，以及初步的RNA-SEQ和CHIP-SEQ实验已经确定 AVM/HHT潜在的新调节因子，包括血管信号蛋白Tek和Angiopoietin 2 (ANG2)和转录辅助因子Zmiz1。这个应用程序的中心目标是回答两个问题 基本问题：AVM/HHT发病的分子和细胞机制是什么 哪些是转化生长因子β通路的下游效应因子，促进动静脉畸形/高血压？我们将讨论这些主题 通过检验我们的假设，Smad4转录控制下游途径组件，这些组件是 通过以下具体目标，从机械上负责动静脉畸形的形成：1)确定分子和 导致AVM形成的细胞事件和与AVM/HHT相关的Smad4下游效应因子；2) 检查Tek/Angiopoietin信号在动静脉动静脉畸形的发生和分解中的作用；以及3)检查该信号在动静脉动静脉畸形的发生和分解中的作用 Zmiz1基因在AVM发病机制中的作用从这些研究中获得的结果将促进我们对 AVM发病机制的介导物和发现治疗该疾病的新药靶点 HHT的作用机制。

PROJECT SUMMARY Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant genetic disease that affects males and females from all racial and ethnic groups, and is found in ~1 in every 5000 people. HHT is characterized by inappropriate connections between arteries and veins, called arteriovenous malformations (AVMs). These fragile connections can bleed and rupture leading to anemia, aneurysms, stroke and even death. Remarkably, there are currently no drugs for effective treatment of AVMs in HHT patients, despite the previous identification of the defective signaling pathway associated with HHT. Genetic causes of HHT are linked to the Transforming Growth Factor-β (TGFβ) signaling pathway, with approximately 85% of patients showing mutations in the Endoglin (Eng) or Activin receptor-like kinase 1 (Acvrl1) co-receptors. About 4% have defects in the downstream transcription factor, Smad-related protein 4 (Smad4). Despite many years of HHT research mainly focused on Eng and Acvrl1, two crucial gaps in our knowledge remain - a comprehensive understanding of the cell morphological and biological defects of the HHT vasculature, and identification of the downstream genes that are mechanistically responsible for the vascular defects. We have created a novel mouse model of AVM/HHT whereby genetic ablation of Smad4 specifically in blood vessels effectively replicates the cell biological defects associated with HHT. Using our model we have begun a detailed molecular and cellular characterization of HHT vessels in vivo, and initial RNA-seq and ChIP-seq experiments have identified potential novel regulators of AVM/HHT, including the vascular signaling proteins Tek and Angiopoietin 2 (Ang2), and the transcriptional co-factor Zmiz1. The central objective of this application is to answer two fundamental questions: What are the molecular and cellular mechanisms driving AVM/HHT pathogenesis and what are the downstream effectors of the TGFβ pathway that promote AVM/HHT? We will address these topics by testing our hypothesis that Smad4 transcriptionally controls downstream pathway components that are mechanistically responsible for AVM formation, via the following specific aims: 1) Identify the molecular and cellular events causing AVM formation and the Smad4 downstream effectors associated with AVM/HHT; 2) Examine the role of Tek/Angiopoietin signaling in generation and resolution of AVMs; and 3) Examine the role of Zmiz1 in AVM pathogenesis. Results obtained from these studies will advance our understanding of the mechanistic mediators of AVM pathogenesis and uncover new drug targets designed to treat the disease mechanisms of HHT.