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

标题：依赖休眠的血液内皮细胞对造血干细胞命运的决定 项目摘要/摘要： 造血干细胞(HSCs)，以其同时具有多系血细胞的能力为唯一定义 形成和终身自我更新，是治疗和研究血液的宝贵资源 和免疫紊乱。产生造血干细胞的方法，例如从多能干细胞(PSCs)中产生，有 非常感兴趣，因为它们可以显著提高用于研究和治疗目的的造血干细胞的可用性。 然而，从PSCs生产功能性HSCs的可重复性方案在很大程度上是难以捉摸的。这很有可能 反映了我们对HSC规范所需的分子程序的不完全理解 胚胎发育。该项目的主要目标是通过确定 将HSC命运从胚胎前体传给造血者所需的独特因素 内皮细胞(HE)。为了实现这一目标，我们将利用创新的体外血管利基平台 支持发展小鼠胚胎造血干细胞，结合综合单细胞技术，以 揭示HE独特的分子特性，可以在体外获得功能强大的HSC命运。在初步研究中 使用这种方法，我们确定了具有HSC能力的HE具有唯一的转录签名 以相对代谢和有丝分裂休眠为特征，伴随着MYC靶基因活性的降低。 我们进一步确定HSC在体外的出现依赖于利基来源的趋化因子CXCL12和 其受体CXCR4在具有HSC活性的HE上表达。基于这些研究，我们假设 HSC能力性HE的休眠状态具有延迟造血分化和建立自我的功能。 对HSC规范至关重要的更新计划，将在目标1中进行测试。我们进一步假设 CXCL12-CXCR4信号加强了HE中的休眠和自我更新程序，支持他们向 血管壁龛中的功能性造血干细胞，将在目标2中进行测试。我们更广泛的目标是确定 小鼠和人HE诱导过程中信号通路的调节是否促进休眠 PSCs在体外可以促进功能性HSC的发育，这将在目标3中进行探索。 研究将为协调HSC发生的分子机制提供新的见解，并促进 向从PSCs中从头生成用于治疗应用的HSC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.