Biochemistry of Leukemia Virus Core Binding Factor

描述（由申请人提供）：Runx 1-CBFbeta转录因子是所有永久造血细胞出现所必需的。它是胚胎中造血干细胞和祖细胞产生部位的最早特异性标志物。Runx 1在内皮细胞、间充质细胞和主动脉内造血簇中以及在所有定向造血祖细胞和可移植干细胞中表达。我们假设Runx 1-CBFbeta是必需的，至少部分是在胎儿发育过程中“生血内皮”和造血细胞之间的过渡。然而，如果Runx 1在成年小鼠中缺失，在造血建立后，长期再生的造血干细胞持续存在，定向红系、髓系和巨核细胞祖细胞的数量增加，红细胞生成和终末粒细胞分化都是正常的。因此，Runx 1-CBFbeta绝对需要在胎儿中建立造血，但不是在成人中维持造血的所有方面。我们的目标之一是确定Runx 1-CBFbeta在孕体中指定确定性造血所需的发育窗口和细胞类型。第二个目标是最近的发现，即胎盘可能是造血干细胞的来源。我们将确定造血干细胞在胎盘中的位置，以及它们是否从尿囊或胎盘迷路中的内皮细胞分化。最后，我们将试图确定信号源，诱导Runx 1的表达和明确的造血在孕体的第一波。我们将专门研究刺猬，在斑马鱼中的造血所需的信号级联的上游组件，激活Runx 1的表达和小鼠孕体中的造血。这些目标将有助于我们了解在小鼠孕体中建立确定性造血的最早事件，并有助于指导体外从胚胎来源产生血细胞的努力。

DESCRIPTION (provided by applicant): The Runx1-CBFbeta transcription factor is required for the emergence of all definitive hematopoietic cells. It is the earliest specific marker of sites from which hematopoietic stem and progenitor cells are produced in the conceptus. Runx1 is expressed in endothelial cells, mesenchymal cells, and in intra-aortic hematopoietic clusters, and in all committed hematopoietic progenitors and transplantable stem cells. We hypothesize that Runx1-CBFbeta is required, at least in part, for the transition between "hemogenic endothelium" and hematopoietic cells during fetal development. However, if Runx1 is deleted in adult mice, after hematopoiesis is established, long-term repopulating hematopoietic stem cells persist, committed erythroid, myeloid, and megakaryocytic progenitors increase in number, and both erythropoiesis and terminal granulocyte differentiation are normal. Thus, there is an absolute requirement for Runx1-CBFbeta to establish hematopoiesis in the fetus, but not to maintain all aspects of it in the adult. One of our goals is to define the developmental window and cell types in which Runx1-CBFbeta is required to specify definitive hematopoiesis in the conceptus. A second aim follows up on recent findings that the placenta may be a source of hematopoietic stem cells. We will determine where in the placenta hematopoietic stem cells reside, and whether they differentiate from endothelial cells in the allantois or in the placental labyrinth. Finally, we will attempt to identify the signaling sources that induce the first wave of Runx1 expression and definitive hematopoiesis in the conceptus. We will specifically examine whether Hedgehog, the upstream component of a signaling cascade required for definitive hematopoiesis in zebrafish, activates Runx1 expression and definitive hematopoiesis in the mouse conceptus. Together these aims will contribute to our understanding of the earliest events that establish definitive hematopoiesis in the mouse conceptus, and should help guide efforts to produce blood cells from embryonic sources in vitro.