Metabolic regulation of hematopoietic stem cell function

描述（由申请人提供）：能量代谢如何协调造血干细胞（HSC）维持和谱系分化在很大程度上仍是未知的。干细胞小生境中的缺氧微环境限制了HSC中的线粒体有氧代谢（呼吸/氧化磷酸化），这通过减弱活性氧（ROS）（线粒体呼吸的副产物）的产生来保护该基本细胞库免受氧化损伤。然而，调控HSC代谢活性的细胞内在机制尚不清楚。此外，能量代谢如何与其他调控网络协调HSC分化尚未被表征。缺乏这样的知识阻碍了对与线粒体功能障碍和代谢状况相关的血液疾病的发病机制的理解。PTPMT 1是一种进化上保守的PTEN样磷脂酰肌醇磷酸（PIP）磷酸酶，定位于线粒体内膜，其中存在对线粒体离子稳态和因此代谢重要的离子通道和转运蛋白。我们的初步研究表明，在小鼠中靶向破坏PTPMT 1导致植入后胚胎死亡。诱导型基因敲除（PTPMT 1fl/fl/Mx 1-Cre+）小鼠成年骨髓（BM）细胞中PTPMT 1的缺失损害骨髓和淋巴细胞发育。此外，造血细胞特异性敲除（PTPMT 1fl/fl/Vav 1-Cre+）小鼠的出生后造血被完全阻断。这些小鼠在出生后3-6天内死于全血细胞减少症。值得注意的是，BM中的HSC在PTPMT 1fl/fl/Mx 1-Cre+小鼠和PTPMT 1fl/fl/Vav 1-Cre+新生儿中分别增加了约30倍和约10倍。初步的机制研究表明，PTPMT 1-耗尽细胞的细胞呼吸减少，而糖酵解增强。本申请的目的是扩展这些研究，以进一步确定线粒体磷酸酶PTPMT 1在HSC中的作用和信号转导机制。我们推测PTPMT 1通过调节线粒体代谢来协调HSC的稳态和谱系定型。我们计划通过追求以下两个目标来测试我们的假设并实现本申请的目标。(i)目的明确PTPMT 1在造血中的作用。(ii)确定PTPMT 1调节HSC功能的机制。这项工作是创新的，因为它探索了精细控制的线粒体代谢对HSC维持和谱系分化的意义。所提出的工作的组合，共同预期产生新的见解造血细胞发育的生物能量调节。此外，收集的信息将导致更好地了解线粒体功能障碍和代谢条件导致的血液疾病的病理生理学。

DESCRIPTION (provided by applicant): It remains largely unknown how energy metabolism coordinates hematopoietic stem cell (HSC) maintenance and lineage differentiation. The hypoxic microenvironment in stem cell niches limits mitochondrial aerobic metabolism (respiration/oxidative phosphorylation) in HSCs, which preserves this essential cell reservoir from oxidative damage by attenuating the production of reactive oxygen species (ROS), a byproduct of mitochondrial respiration. However, cell intrinsic mechanisms regulating HSC metabolic activities are poorly defined. Furthermore, how energy metabolism orchestrates HSC differentiation in concert with other regulatory networks has not been characterized. Lack of such knowledge impedes the understanding of the pathogenesis of blood diseases associated with mitochondrial dysfunction and metabolic conditions. PTPMT1, an evolutionarily conserved PTEN-like phosphatidylinositol phosphate (PIP) phosphatase, is localized to the mitochondrial inner membrane where ion channels and transporters, important for mitochondrial ion homeostasis and thus metabolism, reside. Our preliminary studies have shown that targeted disruption of PTPMT1 in mice results in post-implantation embryonic lethality. Deletion of PTPMT1 from adult bone marrow (BM) cells of inducible knockout (PTPMT1fl/fl/Mx1-Cre+) mice impairs myeloid and lymphoid cell development. Moreover, postnatal hematopoiesis in hematopoietic cell-specific knockout (PTPMT1fl/fl/Vav1-Cre+) mice is completely blocked. These mice succumb to pancytopenia within 3-6 days of birth. Strikingly, HSCs in the BM are increased by ~30-fold and ~10-fold in PTPMT1fl/fl/Mx1-Cre+ mice and PTPMT1fl/fl/Vav1-Cre+ neonates, respectively. Preliminary mechanistic studies show that cellular respiration of PTPMT1-depleted cells is decreased while glycolysis is enhanced. The objective of this application is to extend these studies to further determine the role and signaling mechanism of mitochondrial phosphatase PTPMT1 in HSCs. We hypothesize that PTPMT1 coordinates HSC homeostasis and lineage commitment by modulating mitochondrial metabolism. We plan to test our hypothesis and accomplish the objective of this application by pursuing the following two aims. (i) To define the role of PTPMT1 in hematopoiesis. (ii) To determine the mechanisms by which PTPMT1 modulates HSC function. The proposed work is innovative, because it explores the significance of finely controlled mitochondrial metabolism for HSC maintenance and lineage differentiation. The combination of the work proposed is collectively expected to yield novel insights into the bioenergetic regulation of hematopoietic cell development. In addition, the information gathered will lead to a better understanding of the pathophysiology of blood disorders resulting from mitochondrial dysfunction and metabolic conditions.