Lineage bias and clonal expansion of hematopoietic stem cell differentiation

职位描述(申请人提供)：我目前的职业目标是成为一名干细胞的独立研究员，专注于在临床相关压力下的单个细胞水平上的造血干细胞分化。我的长期研究目标是确定在维持平衡的血液系统中，造血干细胞是如何协调的，以及这种协调的调节机制与血液疾病有何关系。在Ihor R.Lemischka博士的指导下，我在普林斯顿大学接受了博士培训，在斯坦福大学的Irving L.Weissman博士的指导下，我在细胞生物学方面拥有专业知识，因此我在分子生物学方面拥有很强的背景。我精通几种编程语言，包括C/C++、R、MatLab和Python语言，能够独立设计和执行现代定量生物学所需的高级统计分析。利用这些跨学科的技术，我最近开发了一种新型的单细胞活体跟踪系统，具有高灵敏度和高通量的特点。我们使用该系统进行的初步研究证实了先前关于小鼠存在HSC谱系偏见的报道。此外，我们还发现了一个以前未被发现的现象：辐射介导的移植后的大多数血细胞来自移植的一小部分HSC克隆的急剧扩张。更引人注目的是，虽然在辐射介导的移植后通常会观察到谱系偏见和克隆性扩张，但在无条件移植后并不存在。因此，我们推测谱系偏向和克隆性扩张不是HSC的先天特征，而是由辐射等外源性造血应激所引发的行为。在这项授权中，我们建议在不同的移植条件下(K99期)在小鼠身上进一步测试这一假说，并确定谱系偏见和克隆扩张是否相关(K99期/R00期)，以及它们是否是HSC克隆的先天确定性特征(R00期)。除了这些体内的小鼠研究外，我们还将在克隆水平上(R00期)研究人HSCs移植到小鼠体内的情况。这些拟议的研究将阐明在破坏后如何重新建立造血平衡，并将辐射诱导的效应与自然的固有细胞特性分开。这一结果将有助于改善与血液系统不平衡相关的疾病的治疗，并可能导致解决方案，在临床应用中和在辐射暴露水平持续较低的职业中减少辐射的副作用。我的K99阶段培训将由著名的造血干细胞专家欧文·L·魏斯曼博士指导，在斯坦福大学医学院干细胞生物学和再生医学研究所世界级的机构环境中进行。除了让我完成拟议的研究外，K99培训还将极大地增强我在研究临床应用方面的知识和经验。此外，它还将帮助我找到一个独立的研究职位，并为我的第一个R01申请做准备提供初步支持。

DESCRIPTION (provided by applicant): My immediate career goal is to become an independent investigator of stem cells, focusing on hematopoietic stem cell differentiation at the single cell level under clinically relevant stresses. My long-term research goal is to determine how hematopoietic stem cells are coordinated in sustaining a balanced blood system and how the regulatory mechanisms of this coordination are related to blood disorders. I have a strong background in molecular biology from my PhD training at Princeton University under the guidance of Dr. Ihor R. Lemischka and expertise in cell biology under the mentoring of Dr. Irving L. Weissman at Stanford University. I am proficient with several programming languages including C/C++, R, Matlab, and Python, and I can independently design and carry out the advanced statistical analyses required for modern quantitative biology. Using these cross-disciplinary skills, I have recently developed a novel, single cell in vivo tracking system featurig high sensitivity and high throughput. Our preliminary studies using this system confirm previous reports of HSC lineage bias in mice. In addition, we have discovered a previously undetected phenomenon: the majority of blood cells after irradiation-mediated transplantation are derived from the dramatic expansion of a small subset of engrafted HSC clones. More strikingly, while lineage bias and clonal expansion are commonly observed after irradiation-mediated transplantation, they are not present after unconditioned transplantation. Therefore, we hypothesize that lineage bias and clonal expansion are not innate HSC characteristics, but instead are behaviors initiated by exogenous hematopoietic stresses such as irradiation. In this grant, we propose to further test this hypothesis in mice under various transplantation conditions (K99 phase) as well as to determine whether lineage bias and clonal expansion are related (K99 phase / R00 phase) and whether they are innate deterministic features of HSC clones (R00 phase). In addition to these in vivo mice studies, we will also investigate human HSCs xenotransplanted into mice at the clonal level (R00 phase). These proposed studies will elucidate how hematopoietic homeostasis is re-established after disruption and will separate irradiation-induced effects from natural innate cellular properties. The results will help to improe the treatment of diseases associated with an unbalanced blood system and may lead to solutions that reduce the side effects of radiation in clinical applications and in occupations wit constant low levels of radiation exposure. My K99 phase training will be mentored by the distinguished hematopoietic stem cell expert Dr. Irving L. Weissman, in a world-class institutional environment at the Institute for Stem Cell Biology and Regenerative Medicine at Stanford University School of Medicine. In addition to allowing me to finish the proposed research, the K99 training will also substantially enhance my knowledge and experience with the clinical applications of my research. In addition, it will help me locate an independent research position and provide the initial support to prepare for my first R01 application.