Notch Signaling in Mouse Arterial-Venous Specification

描述(申请人提供)：我们的长期目标是确定哺乳动物血管系统正常发育和维持的分子机制，并阐明血管发病机制下的分子损伤。最近在斑马鱼上进行的实验表明，Notch的表达促进了动脉的发育，而它的下调导致了静脉的默认发育。尽管在斑马鱼中有这些发现，但小鼠基因敲除实验表明，Notch在乳头动静脉(AV)发育中的作用更为复杂。此外，确切的细胞和分子事件仍有待定义。为了确定Notch通路在小鼠胚胎和成体房室分化中的作用，我们的实验室建立了一个小鼠模型，在该模型中，一种结构上具有活性的Notch形式仅在内皮细胞中表达。此外，激活的Notch表达在时间上是可调节的，从而使我们能够检查它在发育和成年血管系统中的作用。使用该突变体和其他Notch突变体，我们将实现以下特定目标：确定Notch在胚胎房室分化中的作用(目标1)；确定Notch在成人维持房室特性中的作用(目标2)；定义Notch决定动脉和静脉分化的细胞机制(目标3)；以及鉴定Notch在内皮细胞中触发的分子事件(目标4)。这项研究的具体目的，包括形态、细胞和分子分析，需要对内皮细胞中Notch的功能获得和丧失进行研究。这些努力将揭示Notch在血管分化和维持中的作用，并阐明这些过程潜在的分子机制。未来，对Notch在哺乳动物出生前和出生后血管功能的基本了解将指导对其在病理条件下的功能的研究，例如缺血侧支动脉的形成。最终，我们对Notch通路的了解可能会导致识别新的药物靶点和血管疾病的治疗干预。

DESCRIPTION (provided by applicant): Our long-term goal is to ascertain the molecular mechanisms responsible for the normal development and maintenance of the mammalian vasculature and to elucidate molecular lesions underlying vascular pathogenesis. Recent experiments performed on zebrafish have suggested that Notch expression provokes arterial development while its down-regulation results in the default development of veins. Despite these findings in zebrafish, mouse knockout experiments suggest Notch's role in mammilian arterial-venous (AV) development is more complex. Furthermore, the precise cellular and molecular events remain to be defined. To determine the function of the Notch pathway in AV differentiation both in mouse embryos and adults, our lab has developed a mouse model, in which a constituitively active form of Notch is expressed exclusively in endothelial cells. Furthermore, the activated Notch expression is temporally regulatable, thereby allowing us to examine its effects in both developmental and adult vasculature. Using this and other Notch mutants, we will accomplish the following specific aims: define the role of Notch in embryonic AV differentiation (Aim 1); define the role of Notch in adult maintenance of AV identity (Aim 2); define the cellular mechanisms by which Notch specifies differentiation of arteries and veins (Aim 3); and identify the molecular events triggered by Notch in endothelial cells (Aim 4). The specific aims of this study, engaging morphological, cellular, and molecular analyses, entail both gain-and loss-of-function studies of Notch in endothelial cells. These efforts will reveal the role of Notch in vascular differentiation and maintenance and illuminate potential molecular mechanisms underlying these processes. In the future, this basic understanding of Notch in pre and postnatal mammalian vascular function will guide investigations into its function under pathological conditions, such as ischemic collateral artery formation. Ultimately, our understanding of the Notch pathway may lead to the identification of novel drug targets and therapeutic interventions to vascular diseases.