Biochemistry of Leukemia Virus Core Binding Factor

描述(申请人提供)：RUNX1-CBFβ转录因子是所有决定性的造血细胞出现所必需的。它是胚胎中产生造血干细胞和祖细胞的位置的最早的特定标记。RUNX1表达于内皮细胞、间充质细胞、主动脉内造血团，以及所有定向造血祖细胞和可移植干细胞。我们推测，RUNX1-CBFbeta至少部分是胎儿发育过程中“血源性内皮细胞”和造血细胞之间的转换所必需的。然而，如果RUNX1在成年小鼠中缺失，在建立造血后，长期再生的造血干细胞持续存在，承诺的红系、髓系和巨核系祖细胞数量增加，红细胞生成和粒细胞终末分化都是正常的。因此，绝对需要RUNX1-CBFbeta在胎儿中建立造血，但不是在成人中维持它的所有方面。我们的目标之一是定义发育窗口和细胞类型，在该窗口中，RUNX1-CBFbeta被要求指定在胚胎中确定的造血。第二个目标是跟进最近的发现，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，以及它们是否与尿囊或胎盘迷路中的内皮细胞分化。最后，我们将尝试确定在胚胎中诱导第一波RUNX1表达和明确的造血的信号源。我们将专门研究Hedgehog是否激活了小鼠胚胎中RUNX1的表达和最终的造血。Hedgehog是斑马鱼最终造血所需的信号级联的上游成分。这些目标将有助于我们理解在小鼠胚胎中建立明确的造血的最早事件，并有助于指导在体外从胚胎来源生产血细胞的努力。

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.