Notch mediated arterial-venous specification in the mammalian cerebrovasculature

描述(申请人提供)：血管系统在健康和疾病中起主要作用，通过建立刻板印象的血管组织来确保适当的组织灌流。动脉将血液从心脏输送到毛细血管，从而使血管口径不断缩小。毛细血管是动脉-静脉(AV)界面，营养物质和废物与组织发生交换的地方，必然是直径最小的血管。毛细血管后的小静脉依次加入更宽的静脉，使血液回流到心脏。在发育过程中，Notch信号通过促进动脉对静脉内皮细胞的命运，在从内皮细胞(ECs)组装第一个动/静脉对的过程中成为房室规范的关键中介。Notch基因在出生后的血管内皮细胞中持续表达，提示Notch在建立和/或维持出生后的房室组织中具有作用。出生后不久，未成熟的脑血管系统经历了一个形态发生的动态期，在此期间，动脉/毛细血管/静脉的精细组织由大口径房室连接的原始神经丛形成。目前，人们对确保大脑中这种AV组织的基因控制知之甚少。我们假设，Notch信号控制着未成熟哺乳动物脑血管系统中的房室组织，这是通过决定单个内皮细胞从未成熟的房室连接到动脉与静脉的分配。在目标1中，我们假设未成熟脑血管丛内的单个内皮细胞被分配给动脉与静脉，从而允许血管在房室交界处变窄。为了全面分析脑内的房室组织，我们将：1)随着时间的推移，检测未成熟的房室连接内皮细胞中AV标志物的表达；2)监测EC在体内的迁移。在目标2中，我们假设Notch的丢失促进了静脉程序，并增加了大脑中未成熟的房室连接对静脉的EC分配。我们将在未成熟的内皮细胞中特异性地取消Notch信号，并分析其表型后果，与AV标记的表达和EC在脑血管系统中的迁移有关。在目标3中，我们假设激活的Notch促进了动脉程序，并增加了大脑中未成熟的房室连接对动脉的EC分配。我们将在未成熟的血管内皮细胞中特异性地激活Notch信号，并评估与AV标记表达和EC在动脉与静脉中的分配有关的表型效应。在未成熟大脑中血管变窄和回路形成的这一动态时期，血管系统特别容易受到畸形和相关的神经损伤的影响，这突显了适当的房室连接的必要性。这些研究将为目前关于出生后脑血管形态发生的观点提供分子和细胞分辨率，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.