FLT3: Role and regulation in HSC

通过其配体FL通过Flt3受体刺激的信号似乎在造血中起着重要作用。FL与其他因子协同促进体外培养的人淋巴造血干/祖细胞(HSC)的增殖/维持。FL是用于体外培养人HSC的大多数细胞因子和生长因子的鸡尾酒的一部分。FL还刺激树突状细胞、B祖细胞和NK细胞的发育。然而，目前尚不清楚Flt3是否在高质量和/或低质量HSC的增殖、抗凋亡和分化中发挥作用。我们已经开发出非常有效的、特异的Flt3酪氨酸激酶活性小分子抑制剂。利用这些抑制剂，我们可以通过关闭Flt3在不同细胞群中的功能，同时仍然允许其他正常的细胞过程发生。在未来，这些试剂可能被用来补充细胞方法 SAA和GVHD发生在项目1和4。在这个项目中，我们将探索Flt3在低质量和高质量HSC中的生物学功能。对于确定的一组Flt3信号的候选靶点，我们将定义依赖于高质量和低质量HSC中Flt3激活的下游基因表达模式。最后，将研究Flt3在正常HSC中的调节，试图理解为什么Flt3在如此多的白血病中过度表达。 具体目的1：明确Flt3介导的信号转导在高质量HSC和低质量HSC中的作用。特定目的2：确定依赖于Flt3信号的高质量和低质量HSC的候选基因表达谱。特异性目标3：确定在HSC中调节Flt3基因的增强子和转录因子。

Signaling stimulated through the FLT3 receptor by its ligand, FL, appears to play an important role in hematopoiesis. FL synergizes with other factors to enhance the proliferation/maintenance of human lymphohematopoietic stem-progenitor cells (HSC) in vitro. FL is part of most cocktails of cytokines and growth factors being used to culture human HSC ex vivo. FL also stimulates dendritic, B progenitor, and NK cell development. However, it is still unclear at this time whether or not FLT3 plays a role in proliferation, antiapoptosis, and differentiation of high quality HSC and/or low quality HSC. We have developed very potent, specific small molecule inhibitors ofFLT3 tyrosine kinase activity. Utilizing these inhibitors we can probe FLT3 function in different cell populations by shutting it offwhile still allowing other normal cellular processes to take place. These reagents might, in the future, be used to complement the cellular approaches to SAA and GVHD taking place in Projects 1 and 4. Within this project we will probe the biological function of FLT3 in both low and high quality HSC. For an identified set of candidate targets of FLT3 signaling, we will define the downstream gene expression pattern that is dependent on FLT3 activation in high and low quality HSC. Finally, FLT3 regulation in normal HSC will be studied in an attempt to understand why FLT3 is overexpressed in so many leukemias. Specific Aim 1: Define the role of FLT3-mediated signal transduction in high quality HSC and low quality HSC. Specific Aim 2: Determine the candidate gene expression profile dependent on FLT3 signaling in high and low quality HSC. Specific Aim 3: Identify enhancers and transcription factors which regulate the FLT3 gene in HSC.