Stem Cell-Niche Interactions in the Establishment of Hematopoietic Stem Cell Heterogeneity

摘要 在血液中，造血干细胞（HSC）在谱系上存在丰富的多样性， 贡献、增殖、刺激反应和表面标记。虽然已经观察到HSC异质性， 在胚胎发育过程中，它是如何产生的尚不清楚。我的目标是了解克隆多样性 在HSC中，造血干细胞和祖细胞（HSPCs）是由新生的内皮细胞形成的， 生殖腺-中肾（AGM），并暂时定殖于哺乳动物的胎肝或尾 斑马鱼的造血组织（CHT），在归巢到骨骼或肾脏骨髓中的成年龛之前， 分别HSC亚型的行为早在胎肝期就可发现，且非常稳定， 即使在连续移植后，仍保持谱系偏倚。这暗示了一种模式， 在发育过程中，在HSC中建立内在的克隆行为，这种行为在动物的整个生命周期中都持续存在。我 假设AGM和CHT中的信号建立了新出现的和 新生HSC本项目旨在明确胚胎微环境在建立HSC克隆中的作用， 谱系倾斜，并研究候选人的细胞和HSC克隆行为的遗传效应。到 为了实现这一目标，我建立了一种快速富集稀有胚胎细胞的新方法， 障碍，以前阻碍了努力，以衡量这些罕见的发展事件，在高通量 方式目标1中概述的实验将1）鉴定新生HSPC中的转录多样性，以确定 当在干细胞诱导中建立亚型时，和2）测试参与建立亚型的候选途径， HSC亚型。目的2将具体询问原始巨噬细胞在调节新生巨噬细胞中的作用， 通过识别和干扰CHT中细胞-细胞相互作用后诱导的分子变化来检测HSC池。

ABSTRACT Within the blood there is abundant diversity among hematopoietic stem cells (HSCs) in lineage contribution, proliferation, stimuli response, and surface markers. While HSC heterogeneity has been observed during embryonic development, it is unclear how it is generated. My goal is to understand how clonal diversity in HSCs is specified. Hematopoietic stem and progenitor cells (HSPCs) form from budding endothelial cells in the aorta-gonad-mesonephros (AGM), and temporarily colonize the fetal liver in mammals or the caudal hematopoietic tissue (CHT) in zebrafish, before homing to the adult niche in bone or kidney marrow, respectively. HSC subtype behaviors can be found as early as fetal-liver stage and are remarkably stable, with lineage-biases maintained even after serial transplantation. This is suggestive of a model in which early events in development establish intrinsic clonal behavior in HSCs that persists throughout the life of the animal. I hypothesize that signals in the AGM and CHT establish long-lasting clonal differences in emerging and nascent HSCs. This project aims to define the role of embryonic microenvironments in establishing HSC clonal lineage skews and to investigate candidate cellular and genetic effectors of HSC clonal behavior. To accomplish this, I have established a novel method for rapid enrichment of rare embryonic cells, a technical hurdle that has previously hindered efforts to measure these rare developmental events in a high-throughput manner. Experiments outlined in Aim 1 will 1) identify transcriptional diversity in nascent HSPCs to determine when subtypes are established in stem cell induction and 2) test candidate pathways implicated in establishing HSC subtypes. Aim 2 will specifically interrogate the role of primitive macrophages in regulating the nascent HSC pool by identifying and perturbing molecular changes induced after cell-cell interactions in the CHT.