Molecular Pathogenesis of Brain Arteriovenous Malformation

 描述（由申请人提供）：脑动静脉（AV）畸形（BAVM）可导致危及生命的卒中，治疗选择有限。该项目的目标是阐明BAVM发病机制的细胞和分子机制，以确定新的候选人作为治疗靶点，以改善这种疾病。AVM的特征是异常AV分流，使介入毛细血管移位。我们提出了一种跨学科的方法，融合尖端的小鼠遗传学和成像技术，以测试我们的假设，即Notch突变可以重新编程AV身份和改变AV差异一氧化氮（NO）信号传导，从而内皮功能障碍，引发BAVM。Notch受体和配体在动脉中表达，但在静脉中不表达。Notch信号通过增强动脉和抑制静脉分子标志物以静脉分化为代价促进动脉分化。我们已经报道了组成型激活的Notch 4突变（Notch 4 *）的内皮表达可诱导小鼠BAVM。Notch 4 * 重新编程静脉以获得动脉和失去静脉分子身份，并且纠正因果Notch 4 * 导致已建立的BAVM正常化。我们已经建立了一个定制的双光子显微镜，最适合活小鼠脑血管的结构和血流动力学成像。因此，我们可以通过颅窗获得5D数据（3D加上随时间的血流速度），以揭示小鼠BAVM形成的过程。基于我们强大的背景和初步数据，我们提出：目的1 -确定内皮Notch 4 * 对静脉内皮功能障碍和BAVM形成的影响。我们将检验我们的假设，即Notch 4 * 上调静脉中的NO水平，改变静脉内皮对血流的反应，从而允许AVM形成。我们将研究Notch 4 * 对静脉NO信号传导、内皮对血流的反应和血流介导的BAVM形成的影响;目的2 -确定内皮Notch缺陷对动脉内皮功能障碍和BAVM形成的影响。我们将检验我们的假设，即内皮Notch基因功能的丧失减少了动脉NO信号传导，导致动脉功能障碍，从而导致AVM。我们将分析内皮缺失Rbpj的小鼠的BAVM病理学、动脉NO信号传导和内皮对血流刺激的反应;目的3 -比较Notch和Alk 1小鼠突变体在DA和CV发育和BAVM形成中的作用。我们将检验我们的假设，即Notch与遗传性出血性毛细血管扩张症（HHT）2（或Alk 1）在AV分化和AVM形成中相互作用。我们将使用双光子成像和3D渲染比较Notch和HHT突变体表型，并进行遗传拯救。这项研究的结果将在概念上推进我们对AVM发病机制的细胞和分子机制的理解，揭示Notch在调节动脉和静脉独特生理学方面的新功能，并揭示Notch和HHT通路之间的相互作用。这项工作的成功将激发AVM、Notch信号传导和血管病理生理学领域的新研究领域。

 DESCRIPTION (provided by applicant): Brain arteriovenous (AV) malformations (BAVMs) can cause life-threatening strokes and have limited treatment options. The goal for this project is to elucidate the cellular and molecular mechanisms underlying BAVM pathogenesis to identify novel candidates as therapeutic targets to ameliorate this disease. AVMs are characterized by abnormal AV shunts that displace intervening capillaries. We propose a cross-disciplinary approach, fusing cutting-edge mouse genetics and imaging technologies, to test our hypothesis that Notch mutations can reprogram AV identity and alter AV differential nitric oxide (NO) signaling, and thus endothelial dysfunction, to elicit BAVMs. Notch receptors and ligands are expressed in arteries but not veins. Notch signaling promotes arterial at the expense of venous differentiation by enhancing arterial and suppressing venous molecular markers. We have reported that endothelial expression of a constitutively active Notch4 mutation (Notch4*) elicits BAVMs in mice. Notch4* reprograms veins to gain arterial and lose venous molecular identity, and correcting the causal Notch4* leads to normalization of established BAVMs. We have built a custom two-photon microscope, optimal for structural and hemodynamic imaging of cerebral vasculature in live mice. We can thus obtain 5D data (3D plus blood velocity over time) through a cranial window to reveal the process of BAVM formation in mice. Built on our strong background and preliminary data, we propose: Aim 1 - Determine the effect of endothelial Notch4* on venous endothelial dysfunction and BAVM formation. We will test our hypothesis that Notch4* upregulates NO levels in the veins, alters venous endothelial response to blood flow, and thus permits AVM formation. We will examine the effect of Notch4* on venous NO signaling, endothelial response to blood flow, and flow mediated BAVM formation; Aim 2 - Determine the effect of endothelial Notch deficiency on arterial endothelial dysfunction and BAVM formation. We will test our hypothesis that loss of endothelial Notch gene function reduces arterial NO signaling, leading to arterial dysfunction and thus AVMs. We will analyze mice with endothelial deletion of Rbpj for BAVM pathology, arterial NO signaling, and endothelial response to blood flow stimuli; Aim 3 - Compare Notch and Alk1 mouse mutants in DA and CV development and BAVM formation. We will test our hypothesis that Notch interacts with Hereditary Hemorrhagic Telangectasia (HHT) 2 (or Alk1) in AV differentiation and AVM formation. We will compare the Notch and HHT mutant phenotypes using two-photon imaging and 3D rendering and perform genetic rescue. The findings from this study will conceptually advance our understanding of the cellular and molecular mechanisms of AVM pathogenesis, reveal novel functions for Notch in regulating the unique physiology of arteries and veins, and uncover interactions between the Notch and HHT pathways. The success of this work will inspire new areas of investigation in the fields of AVMs, Notch signaling, and vascular pathophysiology.