Clonal analysis of hematopoietic stem and progenitor biology in situ

 描述（由申请人提供）：目前的教条表明，所有血淋巴细胞谱系都来自一个共同的祖先，即造血干细胞（HSC）。HSC被认为是骨髓（BM）中唯一具有长期自我更新能力的细胞，并且通常被认为是成人生命期间连续多谱系血液产生的起源细胞。支持这种以HSC为中心的范例的证据已经通过几十年的工作获得，主要基于使用涉及移植的功能测定。然而，目前尚不清楚在移植条件下测定的细胞的功能特征在多大程度上与驱动非移植天然造血的细胞共有。由于历史上缺乏易处理的系统，非移植血液生产的机械性质在很大程度上仍未被探索。为了解决这一限制，我的实验室在小鼠中开发了一种新的实验系统，可以在原位对细胞进行独特的遗传标记。使用该系统，可以在天然环境中首次随时间和跨谱系追踪多个造血群体的克隆命运。我们对这个模型的初步发现揭示了未受干扰的造血的惊人的独特特征。除此之外，我们的数据表明，长期的天然造血主要是由祖细胞募集波驱动的，在这个过程中HSC的贡献是最小的。因此，我们假设天然造血是由与移植根本不同的机制驱动的。在这项提案中，我们的目标是扩展我们早期的发现，并提供全面的见解血液生产的生物学原位。具体来说，我们将测试HSC是否可以通过损伤，压力或感染招募到生产性造血。我们还将测试祖细胞募集是否会在衰老过程中耗尽。此外，我们将使用克隆策略重新审视经典祖先种群和谱系关系的存在。该项目的完成将阐明血液产生的基本机制，并提供疾病过程中干细胞动力学的见解。

 DESCRIPTION (provided by applicant): Current dogma suggests that all hematolymphoid lineages are derived from a common ancestor, the hematopoietic stem cell (HSC). HSCs are believed to be the only cells with long-term self-renewal capacity in the bone marrow (BM), and are generally regarded as the cell of origin for continuous multi-lineage blood production during adult life. Evidence supporting this HSC-centric paradigm has been acquired through decades of work based largely on the use of functional assays involving transplantation. However, it is unclear to what extent functional characteristics of cells assayed under transplantation conditions are shared with cells driving non-transplant native hematopoiesis. Because of a historical lack of tractable systems, the mechanistic nature of non-transplant blood production has remained largely unexplored. To address this limitation, my laboratory has developed a novel experimental system in mice where cells can be uniquely and genetically labeled in situ. Using this system, clonal fate of multiple hematopoietic populations can be tracked over time and across lineages, for the first time, in a native context. Our preliminary findings with this model have revealed surprisingly unique features of unperturbed hematopoiesis. Among other things, our data demonstrate that long-term native hematopoiesis is mainly driven by waves of progenitor recruitment and that HSC contribution during this process is minimal. Thus, we hypothesize that native hematopoiesis is driven by fundamentally different mechanisms as transplantation. In this proposal, we aim to extend our earlier findings and to provide comprehensive insight into the biology of blood production in situ. Specifically, we will test whether HSCs can be recruited into productive hematopoiesis via injury, stress, or infection. We will also test whether progenitor recruitment can exhaust during the aging process. Additionally, we will revisit the existence of classical progenitor populations and lineage relationships using our clonal strategy. Completion of this project would elucidate the basic mechanisms underlying blood production and provide insight into stem cell dynamics during disease processes.