Epigenetic Regulation of Hematopoietic Stem Cell Specification

摘要白血病是一种细胞功能紊乱、基因表达异常和持续存活的多面性疾病。白血病细胞的一些特征让人想起干细胞的功能，比如自我更新的能力。癌细胞如何获得或重新获得这些特征尚不清楚，尽管染色质重塑的作用被认为是易位产物中染色质重塑因子的存在。同样，关于造血干细胞（HSC）发育中染色质重塑的许多问题仍然未知。在这里，我们建议用斑马鱼作为模型系统来发现调节HSC规格的染色质重塑因子。为此，我们将阐明Polycomb家族染色质重塑蛋白在造血中的作用，并建立Polycomb活性与Wnt和Notch通路之间的层次关系，这两个通路在造血规范和维持中都是必不可少的。我们还将使用基于morpholino的基因表达敲低方法进行反向遗传筛选，以揭示建立HSC和HSC表观遗传密码所需的因素。由于许多与白血病相关的途径和调节因子也控制造血，因此确定造血干细胞规范和维持的基本机制将阐明癌变病变利用的正常细胞功能中的关键因素，从而成为治疗方法的目标。

DESCRIPTION (provided by applicant): Epigenetic Regulation of Hematopoietic Stem Cell Specification SUMMARY Leukemia is a multifaceted disease of disrupted cell function, aberrant gene expression and sustained survival. Some characteristics of leukemia cells are reminiscent of stem cell functions, such as the ability for self-renewal. How cancer cells obtain or re-acquire these characteristics remains unknown, though a role for chromatin remodeling is suggested by the presence of chromatin remodeling factors in translocation products. Similarly, much remains unknown regarding chromatin remodeling in hematopoietic stem cell (HSC) development. Here, we propose to uncover chromatin remodeling factors that regulate HSC specification using zebrafish as a model system. To this end, we will elucidate the role of the Polycomb family of chromatin remodelers in hematopoiesis and establish a hierarchy for Polycomb activity in relation to the Wnt and Notch pathways, both essential in hematopoietic specification and maintenance. We will also conduct a reverse genetic screen using a morpholino-based gene expression knockdown approach to reveal factors necessary for the establishment of HSCs and the HSC epigenetic code. As many of the pathways and regulators associated with leukemia also control hematopoiesis, defining the basic mechanisms of HSC specification and maintenance will illuminate critical factors in normal cell function that cancerous lesions exploit and thus be targeted in therapeutic approaches. PUBLIC HEALTH RELEVANCE: The studies outlined in this proposal will identify factors that alter hematopoietic stem cell development and, when misregulated, may contribute to a leukemic phenotype. Our work aims to identify novel leukemic markers and more accurately determine a diagnosis and prognosis for leukemia patients. Furthermore, knowledge of specific genetic defects may help in selecting a particular course of treatment and may be useful in developing new therapies.