Dormancy-dependent determination of hematopoietic stem cell fate from hemogenic endothelium

标题：生血内皮细胞中造血干细胞命运的休眠依赖性测定 项目概要/摘要： 造血干细胞（HSC），独特的定义是它们同时具有多谱系血细胞的能力， 形成和终身自我更新，代表了治疗和研究血液的宝贵资源 和免疫紊乱。从头产生HSC（例如从多能干细胞（PSC））的方法是： 这是一个巨大的兴趣，因为它们可以显着提高HSC的可用性用于研究和治疗目的。 然而，从PSC生产功能性HSC的可重复方案在很大程度上是难以捉摸的。这可能 反映了我们对HSC规格所需的分子程序的不完全理解， 胚胎发育本项目的主要目标是通过确定 造血干细胞从胚胎前体细胞到造血、造血干细胞 内皮细胞（HE）。为了实现这一目标，我们将利用创新的离体血管利基平台， 支持鼠胚胎HSC的开发，结合整合的单细胞技术， 揭示了HE的独特分子特性，可以在体外获得功能性HSC命运。在初始研究中 使用这种方法，我们确定HSC-感受态HE具有独特的转录特征， 其特征在于与降低的MYC靶基因活性相关的相对代谢和有丝分裂休眠。 我们进一步确定HSC在体外的出现依赖于小生境来源的趋化因子CXCL 12， 其受体CXCR 4在HSC感受态HE上表达。基于这些研究，我们假设， HSC-活性HE的休眠状态起到延迟造血分化和建立自身造血功能的作用。 更新计划对HSC规范至关重要，将在目标1中进行测试。我们进一步假设， CXCL 12-CXCR 4信号转导增强HE中的休眠和自我更新程序，支持它们向 在血管生态位中的功能性HSC，这将在目标2中进行测试。我们更广泛的目标是确定 在小鼠和人类HE特化过程中，是否调节信号通路促进休眠 PSC可以增强体外功能性HSC发育，这将在目标3中进行研究。成功在这些 研究将为HSC发生的分子机制提供新的见解， 从PSC重新产生HSC用于治疗应用的长期目标的进展。

Title: Dormancy-dependent determination of hematopoietic stem cell fate from hemogenic endothelium Project Summary/Abstract: Hematopoietic stem cells (HSCs), uniquely defined by their simultaneous capacity for multilineage blood cell formation and life-long self-renewal, represent a valuable resource for both the treatment and study of blood and immune disorders. Methods to generate HSCs de novo, such as from pluripotent stem cells (PSCs), are of great interest, as they could significantly enhance availability of HSCs for research and therapeutic purposes. However, reproducible protocols to produce functional HSCs from PSCs have been largely elusive. This likely reflects our incomplete understanding of the molecular programs required for HSC specification during embryonic development. The primary objective of this project is to address this critical barrier by identifying the unique factors necessary to impart HSC fate from the embryonic precursors to hematopoiesis, hemogenic endothelium (HE). Toward this goal, we will leverage an innovative ex vivo vascular niche platform that supports the development of murine embryonic HSCs, combined with integrated single cell techniques, to uncover the distinctive molecular properties of HE that can acquire functional HSC fate in vitro. In initial studies using this approach, we determined that HSC-competent HE possess a transcriptional signature uniquely characterized by relative metabolic and mitotic dormancy associated with decreased MYC target gene activity. We further determined that HSC emergence in vitro is dependent on niche-derived chemokine, CXCL12, and that its receptor, CXCR4, is expressed on HSC-competent HE. Based on these studies, we hypothesize that the dormant state of HSC-competent HE functions to delay hematopoietic differentiation and establish self- renewal programs essential for HSC specification, which will be tested in Aim 1. We further hypothesize that CXCL12-CXCR4 signaling reinforces dormancy and self-renewal programs in HE, supporting their transition to functional HSCs in the vascular niche, which will be tested in Aim 2. Our broader objective is to determine whether modulation of signal pathways promoting dormancy during HE specification from murine and human PSCs can enhance functional HSC development in vitro, which will be pursued in Aim 3. Success in these studies would provide new insight into the molecular mechanisms orchestrating HSC genesis and facilitate progress toward the long-term goal of de novo generation of HSCs from PSCs for therapeutic applications.