Metabolic regulation of stem cell niche development and function

项目摘要 造血干细胞（HSC）和祖细胞受到细胞内在机制和细胞外基质的严格调控。 微环境（也称为小生境）由专门的骨髓（BM）基质细胞创建。然而，在这方面， 干细胞或祖细胞龛是如何发展、维持和重塑以应对压力的， 表征了缺乏这些基础知识阻碍了我们理解某些血液学的能力。 直接或间接涉及BM微环境的疾病。HSC是一种前体细胞， 在胚胎发育过程中，血液谱系维持在离散的解剖微环境中， 它们最终在围产期从胎儿肝脏迁移到BM（“归巢”）。然而我们对 管理这一进程的机制仍然有限。我们以前证明了一个重要的细胞内在作用， PTPMT 1是一种基于血小板的Pten样磷脂酰肌醇磷酸磷酸酶， 发育-从造血系统中敲除PTPMT 1导致造血功能衰竭， 生物能量/代谢应激、细胞周期阻滞和HSC分化阻滞。使用PTPMT 1敲除 模型，我们最近研究了协调细胞代谢在干细胞微环境中的作用， 产生和表征PTPMT 1fl/fl/Prx 1-Cre+小鼠，其中PTPMT 1从BM基质细胞中缺失 (and肢芽祖细胞衍生的其它间充质细胞）。令人惊讶的是，从BM基质中缺失PTPMT 1， 细胞导致严重的造血缺陷：1）。近80%的PTPMT 1fl/fl/Prx 1-Cre+小鼠死亡 出生后3周内。HSC（野生型）从胎肝向骨髓的迁移/归巢在胎鼠中受损。 这些动物-与对照小鼠相比，敲除小鼠BM中的HSC减少约5倍2 在出生后10周，而在基因敲除小鼠的肝脏中存在约13倍的造血灶（CD 45+）。2）。 在PTPMT 1 fl/fl/Prx 1-Cre+小鼠中，B淋巴细胞发育被阻断在前B期。这些引人注目 观察使我们假设PTPMT 1介导的代谢在建立或 维持骨髓中的支持性干细胞小生境。本提案的目的是进一步确定 潜在的细胞和分子机制。通过研究这种特殊的线粒体蛋白，我们的目标是 阐明HSC生态位发育/维持/重塑的代谢调控。我们计划测试 通过追求以下三个目标的假设。1）。为了鉴定PTPMT 1缺失的小生境细胞- 诱导的生物能量/代谢应激导致围产期发育期间HSC归巢缺陷。2）。到 确定HSC小生境细胞中PTPMT 1介导的代谢与稳态和 对成人的造血有压力。3）。为了鉴定解释PTPMT 1作用的生物活性分子， 从HSC上的小生境中消耗，以及PTPMT 1缺陷重新编程细胞的机制 新陈代谢.

Project Summary Hematopoietic stem cells (HSCs) and progenitors are tightly regulated by both cell intrinsic mechanisms and the microenvironment (also known as niches) created by specialized bone marrow (BM) stromal cells. However, how stem cell or progenitor niches are developed, maintained, and remodeled in response to stress is poorly characterized. Lack of such fundamental knowledge hinders our ability to understand certain hematological diseases directly or indirectly involving the BM microenvironment. HSCs, the precursor cells that give rise to all blood lineages, are maintained in discrete anatomical microenvironments during embryonic development, and they ultimately migrate from the fetal liver to the BM (“homing”) at the perinatal stage. Yet our understanding of the mechanisms regulating this process remains limited. We previously demonstrated a crucial cell-intrinsic role of PTPMT1, a mitochondria-based Pten-like phosphatidylinositol phosphate phosphatase, in hematopoietic cell development − Knockout of PTPMT1 from the hematopoietic system resulted in hematopoietic failure due to the bioenergetic/metabolic stress, cell cycle arrest, and differentiation block of HSCs. Using the PTPMT1 knockout model, we recently examined the role of coordinated cellular metabolism in the stem cell microenvironment by generating and characterizing PTPMT1fl/fl/Prx1-Cre+ mice, in which PTPMT1 was deleted from BM stromal cells (and limb bud progenitor-derived other mesenchymal cells). Surprisingly, deletion of PTPMT1 from BM stromal cells resulted in profound hematopoietic defects: 1). Nearly eighty percent of PTPMT1fl/fl/Prx1-Cre+ mice died within 3 weeks of birth. The migration/homing of HSCs (wild-type) from the fetal liver to the BM was impaired in these animals – HSCs in the BM of knockout mice decreased by ~5-fold compared to those in control mice 2 weeks after birth, while there were ~13 times more hematopoietic foci (CD45+) in the liver of knockout mice. 2). B lymphocyte development was blocked in the pro-B stage in PTPMT1fl/fl/Prx1-Cre+ mice. These striking observations led us to hypothesize that PTPMT1-mediated metabolism plays an important role in establishing or maintaining supportive stem cell niches in the BM. The objective of the current proposal is to further determine the underlying cellular and molecular mechanisms. By studying this particular mitochondrial protein, we aim to decipher the metabolic regulation of HSC niche development/maintenance/remodeling. We plan to test our hypothesis by pursuing the following three aims. 1). To identify the niche cells in which PTPMT1 depletion- induced bioenergetic/metabolic stress causes HSC homing defects during perinatal development. 2). To determine the functional relevance of PTPMT1-mediated metabolism in HSC niche cells to steady-state and stress hematopoiesis in adults. 3). To identify the bioactive molecules that account for the effects of PTPMT1- depletion from the niche on HSCs, and the mechanisms by which PTPMT1 deficiency reprograms cellular metabolism.