骨髓移植治疗血液疾病的核心是利用健康的造血干细胞重建病人造血系统，但该方法存在很多局限，临床上也没有从体外获得大量可移植造血干细胞的有效方案。解决此问题的瓶颈在于虽然已证实造血干细胞是由生血内皮通过内皮-造血转化过程产生的，但关于此过程机制却知之甚少。本课题组前期围绕“造血干细胞产生及分化”开展了一系列工作。这些成果拓展了我们对血液系统发育的认识，然而造血干细胞产生尤其是内皮-造血转化过程仍需要深入系统的研究。本项目拟从体内造血干细胞产生关键阶段的单细胞全基因组转录水平检测入手，寻找并验证生血内皮命运决定和内皮-造血转化（EHT）过程的关键因子，解析信号通路动态调控该过程的分子机制；以体内造血干细胞产生的调控机制为理论基础，利用新发现关键因子和信号的动态调控方式，探索体外诱导并获得大量造血干细胞的新方法，为体外获得有功能的造血干细胞并应用于转化医学提供新思路。

The key of bone marrow transplantation (BMT) for treatment of hematological diseases is to reconstitute hematopoietic system in patients with healthy hematopoietic stem cells (HSCs). However, there are limitations with this BMT method including the lack of BM donors, and allogeneic graft issues, and so far, it is not possible yet to obtain a large amount of transplantable HSCs for clinical application. The bottleneck to address this question is that our understanding on the de novo production of HSCs through endothelial-to-hematopoietic transition (EHT) is still incomplete. Our group has been working on ‘hematopoietic stem cell development and differentiation’ for the past six years and published our work in high profile journals including PNAS, Blood, Nature Communications, Cell Research etc. In this grant proposal, we plan to study the critical stages of HSC development, by using single-cell transcriptome sequencing and other assays, with hope to determine the key factors involved in the EHT process and to define the underlying molecular mechanism. Importantly, these findings derived from in vivo studies will help us design a more realistic and efficient method to generate and/or expand HSCs in vitro or ex vivo for therapeutic use.