HEMATOPOIETIC COMMITMENT: MOLECULAR MECHANISMS

描述（由申请人提供）：我们的长期目标是了解造血系统是如何在发育中的胚胎中建立的。ER 71、Fli 1、Erg、Ets 1、Ets 2、Elk 3和Tel Ets转录因子以及GATA 2和Scl与胚胎发生期间的造血和血管发育相关。它们在造血细胞和内皮细胞中表达。此外，当这些基因中的任何一个失活时，小鼠表现出不同程度的造血和血管缺陷。显然，我们需要了解Ets、GATA 2和Scl下游的基因调控网络存在重叠。事实上，新兴的研究认为Ets-GATA-Ebox基序对造血发育至关重要。例如，Runx 1在造血干细胞中的表达受Ets-GATA-Ebox基序调控。至于Ets因子，目前还不清楚Ets因子的特异性是如何确定的，也不清楚在造血和血管发育中Ets因子之间存在多少功能冗余。我们有令人兴奋的初步数据表明，有一个Ets层次结构，ER 71位于顶部。值得注意的是，与其他Ets因子、GATA 2或Scl缺乏相比，ER 71缺乏导致最严重的造血和血管缺陷。有趣的是，ER 71在胚胎发生过程中的表达是短暂的：它在原始条纹和背主动脉的大血管中表达，在那里造血程序被激活。在后期阶段，卵黄囊、胎肝或 在骨髓中，ER 71表达大大降低，但其它Ets因子表达突出。从这些数据，我们设想ER 71诱导Ets-GATA 2-Scl三联体介导的造血程序激活。在本研究中，我们验证了以下假设：1）ER 71在造血程序诱导中处于Ets转录因子层级的顶部; 2）Ets转录 Ets因子与GATA 2和Scl共同激活原始和确定的造血程序; 3）Ets因子与GATA 2和Scl三联体是动态的，其中Ets因子将决定具有Ets GATA Ebox基序的靶基因的特异性和随后的细胞命运。Aim 1将决定ER 71在造血诱导中发挥作用的时间窗口。Aim 2将确定ER 71位于Ets层级的顶部并直接激活Ets基因表达。Aim 3将确定ER 71介导的Ets活化导致协同的Ets-GATA 2-Scl靶基因活化和造血程序诱导。这个主题是造血和血管领域发育生物学的基础。这项工作的成功完成将使我们更深入地了解胚胎发育过程中造血系统是如何建立的。这些知识也将直接适用于再生生物学和医学、骨髓造血和造血障碍等多能干细胞研究。

DESCRIPTION (provided by applicant): Our long-term goal is to understand how the hematopoietic system is established in the developing embryo. ER71, Fli1, Erg, Ets1, Ets2, Elk3 and Tel Ets transcription factors as well as GATA2 and Scl are relevant for hematopoietic and vascular development during embryogenesis. They are expressed in hematopoietic and endothelial cells. Moreover, mice display varying degrees of hematopoietic and vascular defects when any of these genes is inactivated. Clearly, there is an overlap in the gene regulatory network downstream of Ets, GATA2 and Scl that we need to understand. Indeed, emerging studies argue that Ets-GATA-Ebox motif is critical for hematopoietic development. For example, Runx1 expression in hematopoietic stem cells is regulated by the Ets-GATA-Ebox motif. As for Ets factors, it is not yet apparent how the Ets factor specificity is determined nor how much of the functional redundancy exists among Ets factors in hematopoietic and vascular development. We have exciting preliminary data suggesting that there is an Ets hierarchy and that ER71 is at the top. Notably, ER71 deficiency leads to the most severe hematopoietic and vascular defects compared to other Ets factors, GATA2 or Scl deficiency. Intriguingly, ER71 expression during embryogenesis is transient: it is expressed in the primitive streak and large vessels of dorsal aorta where definitive hematopoietic program is activated. In later stages yolk sac, fetal liver or bone marrow, ER71 expression is greatly reduced, but other Ets factor expression is prominent. From these data, we envision that ER71 induces Ets-GATA2-Scl triad mediated hematopoietic program activation. In this proposal, we test the following hypotheses: 1) ER71 is at the top of the hierarchy of Ets transcription factors in hematopoietic program induction; 2) Ets transcription factors together with GATA2 and Scl will activate primitive and definitive hematopoietic program; 3) Ets-GATA2-Scl triad is dynamic, in which Ets factors will dictate the specificity of target gene with Ets-GATA-Ebox motif and subsequent cellular fate. Aim1 will determine the window of time that ER71 functions in hematopoietic induction. Aim2 will establish that ER71 is at the top of Ets hierarchy and directly activates Ets gene expression. Aim3 will determine that ER71 mediated Ets activation results in cooperative Ets-GATA2-Scl target gene activation and hematopoietic program induction. This topic is most fundamental to the developmental biology of hematopoietic and vascular fields. Successful completion of the work will lead to a deeper understanding of how hematopoietic system is established during embryogenesis. Such knowledge will also be directly applicable for pluripotent stem cell research on regenerative biology and medicine, bone marrow hematopoiesis and hematopoietic disorders.