Tracking the embryonic origin of the adult haematopoietic system

当接受化疗或放疗的患者接受骨髓移植时，它包括血液干细胞，也称为造血干细胞（hsc），这是正常血液的长期来源。然而，骨髓和脐带移植缺乏，在实验室条件下产生造血干细胞是一个主要的兴趣。虽然造血干细胞是在胚胎发育过程中发育的，但目前尚不清楚如何在培养细胞中复制这一过程。为了了解胚胎产生造血干细胞的机制，研究人员需要首先在胚胎中追踪它们的起源并追踪它们的发育，这是一个令人惊讶的知之甚少的过程。早期胚胎的第一批血细胞在体外形成一种叫做卵黄囊的膜。然而，真正的造血干细胞可以在成年动物体内持续存在，并在发育中的胚胎的特定部位出现。本研究计划的主要目的是确定成人造血干细胞的确切起源位置。鸡胚对这项研究非常有用，因为我们可以在培养皿或鸡蛋中看到它的发育，而不会破坏正常的发育。为此，我们开发了新的工具——表达荧光蛋白的转基因鸡，这样就可以在显微镜下很容易地在活胚胎中跟踪它们的细胞。通过将怀疑含有造血干细胞祖先的区域的精确转基因鸡胚胎组织片段移植到正常的鸡胚胎中，我们将监测它们是否发育成血液。这将使我们能够确定造血干细胞发育的胚胎细胞的确切位置。用不同的荧光报告蛋白标记特定细胞类型的新型转基因鸡株将进一步确定更精确的造血干细胞胚胎祖先定位。这些新工具的发展将为我们识别和表征造血干细胞提供一个独特的机会。从长远来看，这一知识将为开发从胚胎干细胞生成造血干细胞的方法提供信息，用于治疗因化疗或放疗导致造血受损的患者。

When a patient who has undergone chemotherapy or radiotherapy receives a bone marrow transplant, it includes blood stem cells also known as haematopoietic stem cells (HSCs) which are the long-term source of normal blood. However, there is a shortage of bone marrow and umbilical cord transplants and there is a major interest to generate HSCs in the laboratory conditions. Although HSCs develop during embryo development, it is not yet clear how to reproduce this process in cultured cells. To understand mechanisms that the embryo uses to generate HSCs, researchers need to first trace their origin in the embryo and track their development, which is a surprisingly poorly understood process. The first blood cells in the early embryo develop outside its body in a membrane called the yolk sac. However, true HSCs which can persist in the adult animal appear later in a specific part of the developing embryo. The main objective of this research proposal is to identify the precise site of origin of adult HSCs. The chick embryo is very useful for this research as we can see its development in a dish or in the egg, without disrupting normal development. To this end we have developed new tools - transgenic chickens that express fluorescent proteins, so that their cells can be easily followed in live embryos under the microscope. By transplantation of precise transgenic chick embryonic tissue fragments from regions suspected to harbour the ancestors of HSCs into normal chicken embryos we will monitor whether they develop into blood. This will allow us to define the exact location of embryonic cells from which HSCs develop. Novel transgenic chick strains where particular cell types are labelled by different fluorescent reporter proteins will further define more precise localisation of embryonic ancestors of HSCs. The development of these new tools will give us a unique opportunity to identify and characterise HSCs. In the longer terms, this knowledge will inform the development of methods for generation of HSCs from embryonic stem cells for treatment of patients whose blood formation was impaired due to chemo- or radiotherapy.