Role of C-myb in Hematopoiesis and Cancer

描述（由申请人提供）：现已确定c-myb基因编码p75-Myb和p89-Myb两种蛋白，并在造血细胞的发育、增殖和肿瘤发生中起关键作用。由于c-myb基因的组成性缺失会导致胚胎死亡，因此无法准确评估该基因在维持成人造血功能中的作用。为了克服这一问题并研究该基因在成人造血中的功能，我们使用Cre-LoxP重组系统实现了c-myb的组织特异性缺失。在最近发表的一项研究中，我们建立了两个T细胞特异性c-myb敲除小鼠模型mybF/F/LckCre和mybF/F/CD4Cre，它们在T细胞发育的两个特定阶段删除了c-myb。对这些小鼠的研究使我们能够确定c-myb在T细胞发育和功能中的作用。与p75-c-Myb的功能相反，p89c-Myb在造血中的作用尚不清楚。为了检查p89c- myb异构体的功能，我们建立了一个小鼠模型，其中外显子9A被删除，因此，该突变小鼠无法产生p89-c-Myb。当逆转录病毒诱导的小鼠髓性白血病表达C- myb的C端截断形式（称为t-myb）时，证实了C- myb在白血病发生中的作用，其表现出增强的转激活和转化活性。为了确定myb基因截断在小鼠发育和造血过程中的生物学效应，我们培育了一株有条件表达c-Myb c端缺失突变体的小鼠。在这项应用中，我们建议使用这些强大的小鼠遗传模型来确定c-Myb的p75和p89亚型在造血中所起的作用，以及c-Myb的c端截断在造血和白血病发生中的后果。目标是：1。为了确定c-Myb在DP阶段调控t细胞发育的分子机制，将进行基因阵列和蛋白质组学分析，并在体内和体外条件下评估这些改变的基因和蛋白质的功能。2. 确定c-myb在成人造血和骨髓发育中的作用。3. 明确c-myb在造血干细胞（HSC）发育和功能中的作用。4. 确定c-myb的可选剪接形式p89c-myb和c-myb的基因截断形式t- myb在骨髓祖细胞和造血干细胞的谱系承托、增殖和存活中的作用；和5。探讨c-myb在bcrabl介导的髓细胞转化中的作用。

DESCRIPTION (provided by applicant): It is now well established that the c-myb gene encodes for two proteins, p75-Myb and p89-Myb, and plays a critical role in the development, proliferation and oncogenesis of hematopoietic cells. Because constitutive loss of the c-myb gene leads to embryonic lethality, it has not been possible to accurately assess the role of this gene in the maintenance of adult hematopoiesis. To overcome this problem and to investigate the function of this gene in adult hematopoiesis, we used the Cre-LoxP recombination system to achieve tissue-specific deletion of c-myb. In a recently published study, we have generated two T cell-specific c-myb knockout mouse models mybF/F/LckCre and mybF/F/CD4Cre, which delete c-myb at two specific stages of T cell development. Studies with these mice have allowed us to define the role of c-myb in T cell development and function. In contrast to the function of p75-c-Myb, the role of p89c-Myb in hematopoiesis is not known. To examine the function of the p89c- myb isoform, we have generated a mouse model where exon 9A is deleted, and as a consequence, this mutant mouse is incapable of producing the p89-c-Myb. A role for c-myb in leukemogenesis was established when It was shown that retrovirus-induced mouse myeloid leukemias express a C- terminal truncated form of c-myb (termed t-myb), which exhibits enhanced transactivating and transformation activities. To determine the biological effects of myb gene truncation during mouse development and hematopoiesis, we have generated a strain of mice which express a C-terminal deletional mutant of c-Myb conditionally. In this application, we propose to use these powerful mouse genetic models to determine the roles played by p75 and p89 isoforms of c-Myb in hematopoiesis and the consequence of C-terminal truncation of c-Myb in hematopoiesis and leukemogenesis. The aims are: 1. To ascertain the molecular mechanisms by which c-Myb regulates T-cell development at the DP stage, gene array and proteomics analysis will be performed, and the functions of those altered genes and proteins will be assessed using both in vivo and in vitro conditions. 2. To determine the role of c-myb in adult hematopoiesis and myeloid development. 3. To define the role of c-myb in Hematopoietic Stem Cell (HSC) development and function. 4. To determine the roles of an alternatively spliced form of c-myb, the p89c-myb, and a genetically truncated version of c-myb, t- myb, in lineage commitment, proliferation and survival of myeloid progenitors and HSCs; and 5. To examine the role of c-myb in BCRABL-mediated transformation of myeloid cells.