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，可以自我更新并分化为所有血细胞类型。它们构成了治疗白血病和其他癌症的骨髓移植的基础。然而，由于我们对控制HSC细胞命运的细胞外和细胞内信号的理解有限，以及这些细胞在体外扩增的困难，严重阻碍了HSC的临床应用。最近，我发现第15天的小鼠胎肝CD3+Ter119细胞是一种支持HSC扩增的新细胞群。从这些细胞中，我发现胰岛素样生长因子2 （IGF-2）和血管生成素样蛋白2 （Angptl2）是刺激造血干细胞体外扩增的因子。与其他生长因子结合，Angptl2在培养10天内刺激hsc扩增20倍以上。Angptl2在很大程度上未被研究，其受体和信号转导也是未知的。我假设Angptl2与hsc表面上一种目前未知的受体相互作用，从而激活特定的细胞内信号通路并诱导目标基因的转录，这是hsc自我更新或存活所必需的。为此，我们将验证Angptl2、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扩张的假设，并在细胞系和HSC中解剖Angptl2诱导的特定细胞内信号转导途径和转录激活。此外，我将使用表达克隆分离Angptl2细胞表面受体。这项工作将为Angptl2及其膜受体与HSC扩增调节之间的新联系提供新的见解。通过这项研究，申请人将接受高级分子生物学、干细胞生物学、蛋白质生物化学和系统生物学方面的培训，以获得成为独立研究者所需的技能和知识。

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.