MOLECULAR CORRELATES OF HOXB4 FUNCTION

造血干细胞包括一小部分骨髓单个核细胞，它们保持自我更新的能力，并有控制地分化为外周血的所有细胞成分。赋予干细胞表型的分子信号和控制干细胞增殖和分化的机制尚不完全清楚。同源异型盒基因HOXB4在造血干/祖细胞中表达，但在分化程度较高的细胞中不表达。由许多不同的人进行的研究 研究人员已经证明，在造血干细胞中强制表达HOXB4可以增强它们在体内和体外的扩增能力，而不会引发白血病等不良事件。这项建议的总体研究目标是利用目前新兴的基因组规模分析工具，研究HOXB4在干细胞扩增中的分子作用机制。这些分析将包括各种技术，包括基因转移然后诱导转移基因的表达(S)，使用微阵列进行基因表达谱分析，染色质免疫沉淀然后大规模筛选基因组DNA中的HOXB4结合部位，蛋白质-蛋白质相互作用的研究，重组嵌合融合蛋白的功能研究，通过RNA干扰抑制基因表达和蛋白质摄取实验。

Hematopoeitic stem cells comprise a very small faction of bone marrow mononuclear cells, which retain the capacity for self-renewal as well as controlled differentiation into all of the cellular elements of the peripheral blood. The molecular signals that confer the stem cell phenotype and the mechanisms that control stem cell proliferation and differentiation are not completely understood. The homeobox gene HoxB4 is expressed in hematopoietic stem/progenitor cells but not in more differentiated cells. Studies by a number of different investigators have shown that enforced expression of HoxB4 in hematopoietic stem cells leads to enhancement of their ability to expand, both in vivo and in vitro, without inducing adverse events such as the development of leukemia. The overall research goal of this proposal is to investigate the molecular mechanisms of action of HoxB4 in stem cell expansion, using currently emerging tools for genomic scale analysis. These analyses will include a variety of technologies, including gene transfer followed by induced expression of the transferred gene(s), gene expression profiling using microarrays, chromatin immunoprecipitation followed by large scale screening to identify HoxB4 binding sites in genomic DNA, study of protein-protein interactions, functional studies of recombinant chimeric fusion proteins, inhibition of gene expression by RNAi and protein uptake experiments.