Reprogramming Gene Regulatory Networks to a Hematopoietic Stem Cell State

项目概要/摘要 造血是一个连续的过程，血细胞生产发生通过精心策划的活动， 造血干细胞（HSCs）尽管HSC由于其具有以下能力而具有巨大的临床用途： 虽然通过移植重建造血系统，但由于缺乏匹配的造血干细胞， 捐助者。最近，通过诱导重编程因子将内皮细胞直接重编程为HSC， 成为一个有前途的替代品。我们建议的总体目标是揭示分子机制， 其中重编程因子FOSB、GFI 1、RUNX 1和SPI 1（FGRS）使内皮细胞恢复功能， 重编程HSC（reHSC）。了解基因网络为此而重新连接的基础 深刻的细胞类型转换将提供对不同形式的重编程，发育和 疾病我们发现，在重编程过程的早期，FGRS直接协调两项任务： 以及多能HSC增强子的激活和内皮增强子和转录因子的破坏 （TF）。我们假设FGRS对内皮TF结合的影响对于重编程来说与内皮TF结合的影响一样重要。 激活多能性增强子，我们建议剖析这些潜在的分子机制 流程.使用单细胞多组学（scRNA & ATAC-seq）分析，我们进一步发现，在中间体中， 重编程后，相对同质的起始内皮细胞被异质性HSC取代， 人口。从体细胞（内皮）到多能（HSC）调节程序的转变是如何发生的， 经历体外重编程的单个细胞仍然是未知的。为了加强体内重编程，我们 产生了一种新的转基因小鼠模型，该模型允许在所有体细胞组织中恒定表达FGRS， 便于记录导致HSC建立和维护的所有关键分叉事件。基于 我们的研究，我们建议剖析FGRS促进细胞命运的分子和细胞机制 在内皮细胞到HSC重编程的背景下的变化。在我们的第一个目标中，我们将揭示 FGRS靶向和调节内皮和HSC基因调控网络的机制。在第二 目的是，我们将描述促进内皮细胞向HSC转化的内在和外在信号通路。 重新编程我们希望我们的计划将产生对哺乳动物细胞控制的基本见解 鉴定，并可能导致新的策略，以高效率产生治疗相关的HSC。

PROJECT SUMMARY/ABSTRACT Hematopoiesis is a continuous process of blood-cell production occurring through the orchestrated activity of hematopoietic stem cells (HSCs). Although HSCs have tremendous clinical utility due to their ability to reconstitute the hematopoietic system by transplantation, their benefit remains limited by the lack of matched donors. Direct reprogramming of endothelial cells into HSCs via induction of reprogramming factors has recently emerged as a promising alternative. The overall goal of our proposal is to reveal the molecular mechanisms by which the reprogramming factors FOSB, GFI1, RUNX1, and SPI1 (FGRS) revert endothelial cells to functional reprogrammed HSCs (reHSCs). Understanding the basis by which the genetic networks become rewired for this profound cell type conversion will provide insights into diverse forms of reprogramming, development, and disease. We discovered that early in the reprogramming process, FGRS directly coordinate two tasks: selection and activation of multipotent HSC enhancers and disruption of endothelial enhancers and transcription factors (TFs). We hypothesize that the effect of FGRS on endothelial TF binding is as crucial for reprogramming as the activation of multipotency enhancers, and we propose to dissect the underlying molecular mechanisms for these processes. Using single-cell multiomic (scRNA & ATAC-seq) profiling, we further discovered that in intermediate reprogramming, the relatively homogenous starting endothelial cells are replaced by heterogeneous HSC populations. How the transition from somatic (endothelial) to multipotent (HSC) regulatory programs occurs in individual cells undergoing in vitro reprogramming remains unknown. To potentiate in vivo reprogramming, we generated a novel transgenic mouse model that allows constant FGRS expression in all somatic tissues and facilitates the recording of all key bifurcating events that lead to HSC establishment and maintenance. Based on our studies, we propose to dissect the molecular and cellular mechanisms by which FGRS promote cell fate changes in the context of endothelial-to-HSC reprogramming. In our first aim, we will uncover the molecular mechanisms by which FGRS target and modulate endothelial and HSC gene regulatory networks. In the second aim, we will delineate the intrinsic and extrinsic signaling pathways that promote endothelial-to-HSC reprogramming. We expect that our program will yield fundamental insights into the control of mammalian cell identity and may lead to novel strategies to generate therapeutically relevant HSCs with high efficiency.