In vivo role of FLT3-CD45 signalling for bone remodelling

在之前的项目期间，我们利用疾病特异性小鼠模型研究了致癌受体酪氨酸激酶（RTK） FLT3-ITD和蛋白酪氨酸磷酸酶CD45在骨生成调控中的作用。为此，我们详细表征了FLT3-ITD表达小鼠的骨表型，并描述了FLT3-ITD和CD45失活对骨细胞活性的影响以及相关细胞类型的信号特征。因此，该项目阐明了先前未知的FLT3-ITD在骨代谢调节中的作用。这些结果提供了进一步了解正常和病理骨生理。它为骨疾病的靶向影响提供了潜力，以建立改进的治疗方法。除了正在进行的特定项目工作外，我们还开始研究野生型FLT3在骨形成中的作用，使用FLT3敲除小鼠（可在FLI Jena获得）和已建立的用于分析成骨的实验库。我们的初步工作清楚地显示了先前未被注意到的FLT3-WT在骨造血生态位形成中的功能。此外，我们还表征了flt3 - itd阳性和FLT3-WT AML患者的基因表达谱。在这里，我们能够证明致癌FLT3-ITD的合成显著改变了一些参与成骨的成分的表达，它们的合成改变显著地控制了FLT3-ITD- aml患者的生存。此外，我们的初步工作表明，在产生FTL3-ITD的AML患者中发生骨异常。计划项目扩展的目标来自于这项初步工作：i) FLT3灭活小鼠骨表型的详细表征。具体技术可在申请人2和3的骨骼生物学专业实验室获得。ii) FLT3-ITD与FLT3-WT-AML患者的原代骨和细胞材料在骨微观结构、骨转换和参与骨转换的细胞类型特异性活性方面的比较。因此，该项目扩展将阐明flt3介导的信号通路如何控制骨形成和重塑的机制。所涉及的骨细胞类型的分子特征，它们的干细胞生物学和再生能力将描述FLT3在骨代谢中的作用。FLT3-ITD AML患者样本的表征将提供洞察，这种致癌基因如何控制骨重塑，干细胞生态位以及两者在人类中的相互作用。揭示这一机制对于理解正常和病理造血和骨生理学至关重要，并为针对血液学和骨疾病建立改进的治疗方法提供了潜力。

In the previous project period, the role of the oncogenic receptor tyrosine kinase (RTK) FLT3-ITD and protein tyrosine phosphatase CD45 in the regulation of osteogenesis was investigated using disease-specific mouse models. For this purpose, the bone phenotype of FLT3-ITD-expressing mice was characterized in detail, and the influence of FLT3-ITD and the inactivation of CD45 on bone cell activity and the signaling characteristics of the involved cell types was described. Thus, the project elucidated the previously unknown role of FLT3-ITD in the regulation of bone metabolism. These results provide further insight into normal and pathological bone physiology. It provides the potential for the targeted influencing of bone diseases to establish improved therapeutic approaches. In addition to the ongoing project-specific work, we started investigations that address the role of wild-type FLT3 on bone formation using FLT3 knock out mice (available at the FLI Jena) and the established experimental repertoire for the analysis of osteogenesis. Our preliminary work clearly shows a previously unnoticed function of FLT3-WT in the formation of the osteo-hematopoietic niche. Besides, we characterized the gene expression profiles of FLT3-ITD-positive versus FLT3-WT AML patients. Here we were able to show that the synthesis of oncogenic FLT3-ITD significantly alters the expression of a number of components involved in osteogenesis and their altered synthesis significantly controls the survival of FLT3-ITD-AML patients. In addition, our preliminary work has shown bone abnormalities occuring in AML patients that produce FTL3-ITD. The aims of the planned project extension are recruited from this preliminary work: i) The detailed characterization of the bone phenotype of mice inactivated for FLT3. The specific techniques are available in the laboratory of Applicants 2 and 3 specialized in bone biology. ii) Comparison of primary bone and cell material derived from FLT3-ITD with FLT3-WT-AML patients regarding bone microstructure, bone turnover and specific activity of cell types involved in bone turnover. Thus, this project extension will elucidate the mechanisms, how FLT3-mediated signaling pathways control bone formation and remodeling. The molecular characterization of the bone cell types involved, their stem cell biology, and repopulation capacity will describe the role of FLT3 in bone metabolism. Characterization of FLT3-ITD AML patient samples will provide insight, how this oncogene controls bone remodeling, the stem cell niche and the interaction of both in humans. Unraveling this mechanism is critical to understanding normal and pathological hematopoiesis and bone physiology, and provides the potential to target hematological and bone diseases to establish improved therapeutic approaches.