Notch mediated arterial-venous specification in the mammalian cerebrovasculature

描述（由申请人提供）：血管系统在健康和疾病中发挥主要作用，通过建立典型的血管组织来确保适当的组织灌注。动脉将血液从心脏输送到毛细血管，不断减小血管的直径。毛细血管是动脉-静脉（AV）界面，营养物质和废物与组织进行交换，它必然是直径最小的血管。毛细血管后小静脉依次连接较宽的静脉，使血液回流到心脏。在发育过程中，Notch信号已成为内皮细胞（ECs）组装第一对动脉/静脉对时AV规范的关键介质，通过促进动脉/静脉EC的命运。Notch基因在出生后血管内皮中维持表达，提示Notch在建立和/或维持出生后AV组织中起作用。出生后不久，未成熟的脑血管系统经历了一个动态的形态发生时期，在此期间，一个精细的动脉/毛细血管/静脉组织从一个原始的宽孔房室连接丛形成。目前，人们对确保大脑中这种AV组织的遗传控制知之甚少。我们假设Notch信号通过决定单个内皮细胞从未成熟的房室连接到动脉或静脉的分配，控制着未成熟哺乳动物脑血管系统中的房室组织。在Aim 1中，我们假设未成熟脑血管丛内的单个内皮细胞被分配到动脉与静脉，从而允许在房室界面处血管狭窄。为了全面分析脑内的AV组织，我们将：1)随着时间的推移，检查未成熟AV连接内ECs中的AV标记物表达；2)监测EC在体内的迁移。在Aim 2中，我们假设Notch的缺失促进了静脉程序，并增加了EC从大脑中未成熟的AV连接分配到静脉。我们将在未成熟的内皮细胞中特异性地去除Notch信号，并分析与AV标记物表达和内皮细胞在脑血管系统中的迁移相关的表型后果。在Aim 3中，我们假设激活的Notch促进动脉程序，并增加EC从大脑中未成熟的AV连接分配到动脉。我们将在未成熟血管内皮中特异性激活Notch信号，并评估与AV标记物表达和EC分配到动脉与静脉相关的表型效应。在未成熟大脑中血管变窄和电路形成的动态时期，脉管系统特别容易发生异常和相关的神经损伤，强调了适当的房室连接的必要性。这些研究将为目前对产后脑血管形态发生的看法提供分子和细胞的解决方案，并为治疗应用开辟道路。

DESCRIPTION (provided by applicant): The vasculature plays a principal role in health and disease, by establishing stereotypical vessel organization to ensure proper tissue perfusion. Arteries carry blood from the heart to capillaries, successively reducing vessel caliber. Capillaries, the arterial-venous (AV) interface where exchange of nutrients and waste with tissues occurs, are by necessity the smallest diameter vessels. Post-capillary venules join successively wider veins to return blood to the heart. During development, Notch signaling has emerged as a critical mediator of AV specification during assembly of the first artery/vein pair from endothelial cells (ECs), by promoting arterial over venous EC fate. Notch gene expression is maintained in postnatal vascular endothelium, suggesting that Notch has a role in establishing and/or maintaining postnatal AV organization. Shortly after birth, the immature brain vasculature undergoes a dynamic period of morphogenesis, during which a refined organization of arteries/capillaries/veins forms from a primitive plexus of wide-bore AV connections. Currently, little is known about the genetic controls to ensure such AV organization in the brain. We hypothesize that Notch signaling governs AV organization in the immature mammalian cerebrovasculature, by dictating the allocation of individual ECs from immature AV connections to artery vs. vein. In Aim 1, we hypothesize that individual ECs within the immature brain vascular plexus are allocated to artery vs. vein, thereby permitting vessel narrowing at the AV interface. Toward a comprehensive analysis of AV organization within the brain, we will: 1) examine, over time, AV marker expression in ECs within immature AV connections; 2) monitor EC migration in vivo. In Aim 2, we hypothesize that loss of Notch promotes a venous program and increases EC allocation to the vein from immature AV connections in the brain. We will abrogate Notch signaling specifically in immature ECs and analyze the phenotypic consequences, as relate to AV marker expression and EC migration in the cerebrovasculature. In Aim 3, we hypothesize that activated Notch promotes an arterial program and increases EC allocation to the artery from immature AV connections in the brain. We will activate Notch signaling specifically in immature vascular endothelium and assess phenotypic effects, as relate to AV marker expression and EC allocation to artery vs. vein. During this dynamic period of vessel narrowing and circuitry formation in the immature brain, the vasculature is particularly susceptible to aberrations and associated neurological impairments, underscoring the necessity for proper AV connectivity. These studies will provide molecular and cellular resolution toward the current view of postnatal cerebrovascular morphogenesis and open avenues for therapeutic application.