Clonal analysis of hematopoietic stem and progenitor biology in situ

 描述(申请人提供)：目前的教义表明，所有的血淋巴血统都来自一个共同的祖先，即造血干细胞(HSC)。造血干细胞被认为是骨髓中唯一具有长期自我更新能力的细胞，通常被认为是成人生命中持续多谱系造血的起源细胞。支持这种以HSC为中心的范例的证据是通过几十年的工作获得的，这些工作主要基于涉及移植的功能分析的使用。然而，目前尚不清楚在移植条件下检测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相似。由于历史上缺乏可处理的系统，非移植血液产生的机制本质在很大程度上仍未被探索。为了解决这一局限性，我的实验室在小鼠身上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。使用这个系统，可以追踪多个造血群体的克隆命运，这是第一次在本土背景下，跨血统、随时间推移。我们对这个模型的初步发现揭示了令人惊讶的独特的不受干扰的造血功能。此外，我们的数据表明，长期的天然造血主要是由祖细胞招募浪潮驱动的，而HSC在这一过程中的贡献微乎其微。因此，我们假设天然造血是由与移植完全不同的机制驱动的。在这项建议中，我们的目标是扩展我们早期的发现，并对原位血液产生的生物学提供全面的见解。具体地说，我们将测试HSCs是否可以通过损伤、应激或感染被招募到生产性造血中。我们还将测试祖细胞招募是否会在老化过程中耗尽。此外，我们将使用我们的克隆策略重新审视经典祖先种群的存在和血统关系。该项目的完成将阐明血液产生的基本机制，并提供对疾病过程中干细胞动力学的洞察。

 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.