Expansion of hematopoietic stem cells by Angiopoietin-like 2

描述（由申请人提供）：造血干细胞（HSC）是一种罕见的细胞群体，可以自我更新并分化为所有血细胞类型。它们构成了骨髓移植治疗白血病和其他癌症的基础。然而，HSC的临床应用受到我们对支配HSC细胞命运的细胞外和细胞内信号的有限理解以及这些细胞体外扩增的困难的严重阻碍。最近，我确定了第15天的小鼠胎肝CD 3 + Ter 119-细胞作为一种新的细胞群体，支持HSC扩增。从这些细胞中，我鉴定了胰岛素样生长因子2（IGF-2）和血管生成素样蛋白2（Angptl 2）作为刺激HSC体外扩增的因子。与其他生长因子组合，Angptl 2在10天的培养中刺激HSC扩增超过20倍。Angptl 2在很大程度上未被研究，并且其受体和信号转导是未知的。我假设Angptl 2与HSC表面上目前未知的受体相互作用，这导致特异性细胞内信号传导途径的激活和HSC自我更新或存活所需的靶基因转录的诱导。为此，将测试Angptl 2、IGF-2和其他生长因子通过诱导其自我更新和/或存活来刺激HSC扩增的假设，并在细胞系和HSC中剖析由Angptl 2诱导的特异性细胞内信号转导途径和转录激活。此外，我将使用表达克隆来分离Angptl 2细胞表面受体。这项工作将为Angptl 2及其膜受体与HSC扩增调控之间的新联系提供新的见解。通过这项拟议的研究，申请人将接受先进的分子生物学，干细胞生物学，蛋白质生物化学和系统生物学的培训，以获得必要的技能和知识，成为一名独立的研究者。

DESCRIPTION (provided by applicant): Hematopoietic stem cells (HSCs) are a rare population of cells that can self-renew and differentiate into all blood cell types. They form the basis of bone marrow transplantation for treatment of leukemia and other cancers. However, the clinical applications of HSCs are severely hampered by our limited understanding of the extracellular and intracellular signals that govern HSC cell fates and by the difficulty in ex vivo expansion of these cells. Recently I identified day 15 mouse fetal liver CD3+Ter119- cells as a novel cell population that supports HSC expansion. From these cells I identified insulin-like growth factor 2 (IGF-2) and Angiopoietin-like protein 2 (Angptl2) as the factors that stimulate the ex vivo expansion of HSCs. In combination with other growth factors, Angptl2 stimulates a greater than 20-fold expansion of HSCs in 10 days of culture. Angptl2 is largely unstudied and its receptor(s) and signal transduction are unknown. I hypothesize that Angptl2 interacts with a currently unknown receptor on the surface of HSCs, and this results in activation of specific intracellular signaling pathway(s) and induction of transcription of targets gene(s) that are required for self-renewal or survival of HSCs. To this end, will test the hypotheses that Angptl2, IGF-2, and other growth factors stimulate HSC expansion by inducing their self-renewal and/or survival, and dissect the specific intracellular signal transduction pathway(s) and transcriptional activation induced by Angptl2, in both cell lines and in HSCs. Moreover, I will use expression cloning to isolate the Angptl2 cell surface receptor(s). This work will provide new insights into a novel link between Angptl2, its membrane receptor(s), and the regulation of HSC expansion. Through this proposed research, the applicant will receive training in advanced molecular biology, stem cell biology, protein biochemistry, and system biology in order to gain the requisite skills and knowledge to become an independent investigator.