The Role of Geminin in Hematopoiesis

描述(申请人提供)：骨髓中的造血干细胞(HSCs)在一生中为循环提供成熟的血细胞。HSC的分裂既补充了它们自己的数量，又提供了承诺的祖细胞，这些细胞产生了红细胞、白细胞和巨核细胞谱系。祖细胞经历有限数量的分裂，然后分化为成熟的血细胞。祖细胞的分裂和分化必须仔细平衡，以便提供正确的成熟细胞数量和比例。增殖和分化之间的失衡是白血病、淋巴瘤和骨髓增生异常综合征等常见血液学问题的基础。尽管它们显然很重要，但控制细胞持续分裂和末端分化之间选择的机制在很大程度上是未知的。该项目将研究调节蛋白Geminin在造血细胞增殖和分化中的作用。双子座是多能性所必需的，被认为能将分裂的细胞维持在未分化状态。双黄素是一种双功能蛋白，它控制DNA复制的程度，并抑制同源结构域(Hox)转录因子，这些转录因子被认为是造血的关键调节因子。Ginin基因敲除激活Fanconi贫血途径，并在P53-/-T细胞中过表达Ginin抑制的复制因子CDT1，加速淋巴母细胞淋巴瘤的发展。我们正在使用条件性基因敲除策略来研究双子座在最终造血中的作用。在干扰素诱导的Mx-1启动子的控制下，基因靶向的小鼠正在被培育成表达Cre重组酶的小鼠，其中loxP位点位于GMinin基因的基本外显子的两侧。这些小鼠将被多聚肌苷-多胞苷(Poly I：C)处理，以诱导Cre重组酶并删除造血细胞中的Gminin基因。我们将确定双子座丢失如何影响骨髓细胞分裂和分化的模式，双子座如何调节造血细胞的细胞周期，以及双子座是否抑制白血病或淋巴瘤的发展。我们希望对正常造血有更全面的认识，为恶性血液病的治疗寻找新的靶点。项目叙述骨髓中的干细胞在人的一生中不断分裂，以产生成熟的血细胞。生长中的血细胞分裂或成熟的问题会导致白血病和淋巴瘤，这是最常见的两种癌症。这个项目研究了双生蛋白在控制血细胞发育中的作用。

DESCRIPTION (provided by applicant): Hematopoietic stem cells (HSCs) in the bone marrow supply the circulation with mature blood cells throughout life. Division of the HSCs both replenishes their own numbers and provides committed progenitor cells that give rise to the erythrocyte, leukocyte, and megakaryocyte lineages. Progenitor cells undergo a limited number of divisions then differentiate into mature blood cells. Progenitor cell division and differentiation must be carefully balanced in order to provide the correct numbers and proportions of mature cells. Imbalances between proliferation and differentiation underlie common hematological problems like leukemia, lymphoma, and myelodysplastic syndromes. Despite their obvious importance, the mechanisms that control the choice between continued cell division and terminal differentiation are largely unknown. This project will examine the role of the regulatory protein Geminin in the proliferation and differentiation of hematopoietic cells. Geminin is required for pluripotency and is thought to maintain dividing cells in an undifferentiated state. Geminin is a bi-functional protein that controls the extent of DNA replication and inhibits homeodomain (Hox) transcription factors that are known to be crucial regulators of hematopoiesis. Geminin knockdown activates the Fanconi Anemia pathway, and over- expression of the replication factor inhibited by Geminin, Cdt1, in p53-/- T cells accelerates the development of lymphoblastic lymphoma. We are using a conditional knockout strategy to investigate the role of Geminin in definitive hematopoiesis. Gene-targeted mice, in which LoxP sites flank the essential exons of the Geminin gene, are being bred to mice that express Cre recombinase under the control of the interferon-inducible Mx-1 promoter. These mice will be treated with polyinosine- polycytidine (poly I:C) to induce Cre recombinase and delete the Geminin gene in hematopoietic cells. We will determine how Geminin loss affects the pattern of cell division and differentiation in the bone marrow, how Geminin regulates the cell cycle of hematopoietic cells, and whether Geminin suppresses the development of leukemias or lymphomas. We hope to gain a more complete understanding of normal hematopoiesis and identify a new target for therapy of hematological malignancies. PROJECT NARRATIVE Stem cells in the bone marrow continually divide throughout a person's life in order to produce mature blood cells. Problems in the division or the maturation of the growing blood cells give rise to leukemia and lymphoma, two of the most common cancers. This project examines the role of the protein Geminin in controlling blood cell development.