Transgenic Analysis of Platelet Receptor Expression

这项建议的目的是研究控制成熟的分子事件， 巨核细胞、血小板生物发生和正常血小板功能。实验方案利用 转基因动物和变异膜受体的表达。我们的目标是描述 巨核细胞生成过程中发生的独特生物学事件及其后果 正常血小板功能人类Bernard-Soulier综合征（BSS）的鼠模型已经被证实是一种新的动物模型。 通过靶向缺失GP Ib的α-亚基（GP Iba），血小板受体的亚基， GP Ib-IX.小鼠模型显示严重出血表型，伴有巨血小板减少症镜像 人类伯-苏二氏综合征通过表达人GP拯救鼠表型 Iba亚基。新的数据提出建立GP Iba控制血小板的胞质尾区 形态学和血小板从巨核细胞释放。此外，还发现了一条通过 GP Iba的尾部被描述为具有血小板释放和血小板功能的功能性后果。 提出实验来检验假设：i）GP Ib-IX受体控制以下方面： 巨核细胞成熟和血小板通过GP Iba亚基内的结构元件释放，和ii） GP Ib-IX复合物通过受控的信号传导途径促进巨核细胞发育， 也与正常的血小板功能有关。目标1确定GP Iba结构要求 这是促进正常血小板释放所必需的，并定义了导致血小板释放的分子缺陷。 BSS中的巨血小板减少症。目的2描述GP Iba nu_ 老鼠.目的3研究血小板膜糖蛋白Iba的信号转导及其在血小板生成中的作用。目标4确定 基因工程血小板中GP Iba细胞质相互作用的止血相关性。 虽然GP Ib-IX复合物在血小板生成中的作用非常重要，但人们对其了解甚少 反映了缺乏适当的体外模型。然而，模型，如鼠BSS，呈现出一种 有机会研究这些独特的事件，并将提供新的信息机制控制 巨核细胞生成、血小板的释放和血小板在血栓形成中的作用。

The objectives of this proposal are to examine the molecular events controlling maturation of the megakaryocyte, platelet biogenesis and normal platelet function. The experimental plan utilizes transgenic animals and the expression of variant membrane receptor. Our goals are to characterize the unique biological events occurring during megakaryocytopoiesis and the consequences of these events on normal platelet function. A murine model of the human Bernard-Soulier syndrome (BSS) has been established via a targeted deletion of the a-subunit of GP Ib (GP Iba), a subunit of the platelet receptor, GP Ib-IX. The mouse model displays a severe bleeding phenotype with macrothrombocytopenia mirroring the human Bernard-Soulier syndrome. The murine phenotype is rescued by expression of a human GP Iba subunit. New data is presented establishing the cytoplasmic tail of GP Iba controls platelet morphology and platelet release from the megakaryocyte. Moreover, a signal transduction pathway via the tail of GP Iba is described with functional consequences for platelet release and platelet function. Experiments are proposed to test the hypotheses: i) The GP Ib-IX receptor controls aspects of megakaryocyte maturation and platelet release via structural elements within the GP Iba subunit and ii) the GP Ib-IX complex contributes to megakaryocyte development via controlled signaling pathways that also become relevant for normal platelet function. Aim 1 determines the GP Iba structural requirements necessary for facilitating normal platelet release and defines the molecular defect responsible for the macrothrombocytopenia in BSS. Aim 2 characterizes the megakaryocytopoiesis defect in the GP Iba nu_ mouse. Aim 3 characterizes signaling through GP Iba and its role in thrombopoiesis. Aim 4 determines the hemostastic relevance of GP Iba cytoplasmic interactions in genetically engineered platelets. Although clearly important, the role of the GP Ib-IX complex in thrombopoiesis is poorly understood reflecting the lack of appropriate in vitro models. However, models, such as the murine BSS, present an opportunity to study these unique events and will provide new information on the mechanisms controlling megakaryocytopoiesis, the release of blood platelets and role of platelets in thrombus formation.