Molecular pathogenetic mechanisms in CM-AVM

毛细血管畸形-动静脉畸形（CM-AVM）是一种常染色体显性遗传性血管疾病 特征为CM和危及生命的AVM和动静脉瘘。生殖系失活突变 RASA 1基因，其编码RASA 1，RASA 1是Ras信号通路和EPHB 4的负调节因子， 编码EPHB 4生长因子受体的基因，已被确定为大多数CM病例的原因， 反车辆这表明RASA 1和EPHB 4在相同的分子途径中起作用，以保护免受 在这种疾病中，血管（BV）病变的发展。RASA 1和EPHB 4缺陷小鼠的研究 这两种分子都是发育性血管生成所必需的，而这一过程中的缺陷导致了 CM-AVM中BV异常的发生率。然而，RASA 1和EPHB 4如何促进发育 血管生成是未知的。King实验室的一个长期目标是了解Ras信号的作用 在健康和疾病的不同生理系统的途径。本申请的总体目标是， 这是符合这一长期目标，是了解参与发展的分子机制， CM-AVM中BV病变的评价。我们的中心假设是RASA 1-和RASA 2-中Ras信号的失调， EPHB 4缺陷型BV内皮细胞（BEC）导致PLOD 2胶原IV表达增加。 一种修饰酶，主要负责胶原蛋白IV折叠受损，从而导致其保留 在BEC中，它阻止了发育中的血管生成。因此，我们假设，化学物质，协助col- IV层折叠将防止CM-AVM病变的发展。拟议研究的理由是， 他们将告知CM-AVM中BV病变病因学所涉及的分子机制，以及 可能的预防措施。我们计划检验我们的中心假设，从而达到本研究的目的。 通过追求以下三个具体目标来应用：在第一个目标中，我们将使用不同的分子生物学- IC、蛋白质组学和小鼠遗传学方法来确定RASA 1缺陷BEC中Ras信号转导失调。 由于PLOD 2表达增加，naling损害胶原IV折叠和输出。第二个目标， 我们将采用类似的方法来确定EPHB 4的缺失是否通过以下途径损害发育性血管生成： 相同的机制，如果这是由与RASA 1的物理相互作用的缺乏解释。第三 目的，我们将描述一种新的CM-AVM生理嵌合RASA 1缺陷小鼠模型， 用于检测促进IV型胶原折叠的药物预防BV病变发展的能力， 这种疾病。拟议的研究具有创新性，因为使用了新型CM-AVM小鼠模型， Ras信号转导失调与IV型胶原蛋白折叠和输出之间的联系的意外发现。 这些研究具有重要意义，因为它们有可能阐明CM的分子发病机制。 AVM和可能在遗传易感个体中预防病变发展的方法。 !

Capillary malformation-arteriovenous malformation (CM-AVM) is an autosomal dominant vascular disorder characterized by CM and life-threatening AVM and arteriovenous fistulas. Germline inactivating mutations of the RASA1 gene, which encodes RASA1, a negative-regulator of the Ras signaling pathway, and of EPHB4, which encodes the EPHB4 growth factor receptor, have been identified as the cause of most cases of CM- AVM. This suggests that RASA1 and EPHB4 function in the same molecular pathway to protect against the development of blood vascular (BV) lesions in this disease. Studies of RASA1- and EPHB4-deficient mice indi- cate that both molecules are required for developmental angiogenesis and that defects in this process underlie the occurrence of BV abnormalities in CM-AVM. However, how RASA1 and EPHB4 promote developmental angiogenesis is unknown. A long-term goal of the King laboratory is to understand the role of the Ras signaling pathway in different physiological systems in health and disease. The overall objective of this application, which is consistent with this long-term goal, is to understand the molecular mechanisms involved in the devel- opment of BV lesions in CM-AVM. Our central hypothesis is that dysregulated Ras signaling in RASA1- and EPHB4-deficient BV endothelial cells (BEC) results in increased expression of the PLOD2 collagen IV- modifying enzyme that is primarily responsible for impaired folding of collagen IV, thus leading to its retention in BEC, which blocks developmental angiogenesis. Accordingly, we hypothesize that chemicals that assist col- lagen IV folding will prevent the development of CM-AVM lesions. The rationale of the proposed studies is that they will inform upon the molecular mechanisms involved in the etiology of BV lesions in CM-AVM, as well as possible means of prevention. We plan to test our central hypothesis and, thereby, attain the objective of this application by pursuing the following three specific aims: In the first aim, we will use different molecular biolog- ic, proteomic, and mouse genetic approaches to establish that in RASA1-deficient BEC dysregulated Ras sig- naling impairs collagen IV folding and export as a result of increased expression of PLOD2. In the second aim, we will employ similar approaches to determine if loss of EPHB4 impairs developmental angiogenesis through the same mechanism and if this is explained by an absence of physical interaction with RASA1. In the third aim, we will characterize a novel physiological mosaic RASA1-deficient mouse model of CM-AVM that will be used to test the ability of drugs that promote collagen IV folding to prevent the development of BV lesions in this disease. The proposed studies are innovative because of the novel mouse models of CM-AVM used and the unexpected discovery of the link between dysregulated Ras signaling and collagen IV folding and export. The studies are significant because of their potential to illuminate upon the molecular pathogenesis of CM- AVM and ways in which lesion development might be prevented in genetically susceptible individuals. !