Investigating Vegfa transcriptional regulation by co-repressors ETV6 and ETO2 in haematopoietic stem cell development

组织干细胞是具有产生特定器官的所有细胞类型的独特能力的多能细胞。出于这个原因，它们在临床环境中的再生潜力得到了广泛的研究：研究人员的目标是从更不成熟的多能前体细胞（如早期胚胎中的细胞）中“在培养皿中”生产干细胞。为了实现这一雄心勃勃的目标，人们必须能够在体外复制这些早期前体细胞在胚胎体内分化成专门的干细胞时通常整合的发育线索。血液（或造血）系统是研究最好的组织之一，造血干细胞（HSC）通常作为干细胞生物学的范例。然而，到目前为止，还没有人能够成功地在体外产生HSC。因此，有必要全面剖析胚胎中HSC发育的调控机制，以开发维持体外HSC生产的培养条件。血液发育中的一个关键分子是生长因子VEGFA。VEGFA不仅是血管形成所必需的，而且是胚胎发育过程中HSC特化所必需的。我们最近描述了需要这种生长因子来发育HSC的特定阶段。具体地说，我们已经证明了来自分子的不同输入控制VEGFA水平和时空表达的转录调节因子（称为转录调节因子）导致VEGFA在以下方面的不同活性：（i）形成第一批HSC出现的血管，和（ii）我们现在建议进一步研究VEGFA在胚胎中的表达是如何通过表征HSC的性质和功能来控制的。直接参与这一过程的转录调节因子。我们相信这些分子之间复杂的相互作用是VEGFA精确及时表达的原因，我们将致力于剖析它们的作用机制。从长远来看，我们将利用这些信息，以及该领域其他科学家的发现，来确定关键的调控信号，这将有助于在体外制造HSC。这项研究将进一步加深我们对基本生物学过程的理解，并使从事干细胞发育，基因表达调控和VEGFA信号传导的研究人员受益。最终，它将有助于改善人类健康。造血干细胞生产方案的建立将使需要干细胞移植的白血病等血液疾病患者受益。

Tissue stem cells are multipotent cells that have the unique capacity to generate all cell types of a specific organ. For this reason, they are extensively studied for their regenerative potential in clinical settings: researchers are aiming at producing stem cells "in a dish" from more immature, pluripotent precursor cells, such as those present in the early embryo. To achieve this ambitious goal, one will have to be able to reproduce in vitro the developmental cues normally integrated by these early precursors as they differentiate into specialised stem cells in vivo in the embryo. The blood (or haematopoietic) system is amongst the best studied tissues and haematopoietic stem cells (HSCs) often serve as a paradigm in stem cell biology. So far, however, no one has successfully been able to generate HSCs in vitro. A full dissection of the regulatory mechanisms underlying HSC development in the embryo is therefore necessary to be able to develop the culture conditions that will sustain in vitro HSC production. One key molecule in blood development is the growth factor VEGFA. VEGFA is not only necessary for blood vessel formation but also for HSC specification during embryonic development. We have recently described specific stages that require this growth factor for development of HSCs. Specifically, we have shown that distinct inputs from molecules (called transcriptional regulators) that control VEGFA level and spatio-temporal expression lead to the distinct activities of VEGFA in (i) formation of the vessel where the first HSCs emerge and (ii) production of HSCs themselves.We now propose to further investigate how expression of VEGFA is controlled in the embryo through characterisation of the nature and function of the transcriptional regulators directly involved in this process. We believe that a complex interplay between these molecules is responsible for the exquisite timely expression of VEGFA, and we will aim at dissecting their mechanisms of action. In the longer term, we will use this information, together with findings from other scientists in the field, to define the critical regulatory signals that will help make HSCs in vitro.This research will further our understanding of fundamental biological processes and benefit researchers working on stem cell development, regulation of gene expression and VEGFA signaling. Ultimately, it will contribute to the improvement of human health. Establishment of protocols for production of HSCs will benefit patients with blood disorders such as leukaemia who require stem cell transplantation.