转录因子TBX3调控破骨细胞功能与骨质疏松发病机制的研究

Pathogenesis and treatment of osteoporosis became one of the research focus in recent years. Osteoclasts have the unique capacity to resorb bone and play a critical role in bone metabolism. Increased osteoclast activity is the major cause of unbalanced bone remodeling and osteoporosis. Osteoclast-specific gene trancription is one of the key points. Although transcription factors like NFκB, NFAT2 have been shown to play important roles in osteoclasts, they are also widely expressed in other cell lineages and not osteoclast-specific. Recently, few reports showed novel roles of transcription factors in osteoclasts. Our group has identified a new transcription factor TBX3 as an important regulator in osteoclastogenesis and osteoclast function. In order to further investigate the role of TBX3 in bone metabolism, we propose to establish a conditional knock mice model in which TBX3 depletion only occurs in the osteoclast lineage cells. The bone phenotype of osteoclast-specific TBX3 knockout mice will be studied by using Dual-energy X ray analysis,Micro CT and bone histomorphormetry. Based on the mice model, the cellular mechanism in which TBX3 regulates osteoclast differentiation and function will be futher investigated in the aspects of the bone marrow preosteoclast ratio, cell proliferation, apoptosis and mature osteoclasts function. By microarray screens, TBX3-dependent gene expression in osteoclastogenesis will be studied. Genes related to osteoclast function changes will be picked up. The promoter of candidate genes will be analysed and the interaction of TBX3-promoter will be confirmed and studied by ChIP assay. The project we proposed will provide a new vision for the osteoclast research. The molecular research in this study also provides evidences for searching biochemical markers for osteoporosis prevention as well as targets for the possible drug treatment.

骨质疏松症及其骨折的发病机制是目前研究的热点之一，其主要原因是破骨细胞相关基因的转录和调控发生改变，导致其破骨功能亢进。以往发现的破骨细胞转录因子NFκB, NFAT2等在其他细胞中广泛表达，难以作为该细胞特异的分子靶点。目前，破骨细胞转录调控研究鲜有新的相关转录因子被发现。我们的前期研究首次发现了一种新的破骨细胞相关转录因子TBX3，并在体外证明其在调控破骨细胞分化中发挥了重要作用。本课题拟建立特异的破骨细胞TBX3敲除小鼠模型，应用双能量X线，µCT等方法研究TBX3对小鼠骨量的影响及其破骨细胞功能的变化。应用流式细胞术等方法寻找TBX3调控破骨细胞前体分化和成熟细胞骨吸收功能的分子生物学机制。使用基因芯片技术，筛选破骨细胞分化过程中TBX3转录调控的相关基因，通过生物信息学分析及染色质共沉淀技术阐明TBX3对目的基因的转录调控机制，本研究结果将为寻找骨质疏松症防治新靶点提供实验依据。

骨质疏松症及其骨折的发病机制是目前研究的热点之一，其主要原因是破骨细胞相关基因的转录和调控发生改变，导致其破骨功能亢进。目前，破骨细胞转录调控研究鲜有新的相关转录因子被发现。我们的前期研究首次发现了一种新的破骨细胞相关转录因子TBX3，并在体外证明其在调控破骨细胞分化中发挥了重要作用。通过从国外引入相关转基因动物我们成功构建了LysM-Cre介导的破骨细胞内条件性TBX3敲除小鼠模型，并完善了以模式动物为基础的骨质疏松研究平台，并进一步应用组织形态学，µCT等方法研究TBX3对小鼠骨量的影响及其破骨细胞功能的变化。我们发现TBX3基因敲除小鼠与对照组相比骨密度，骨组织内破骨细胞数量及功能均无显著差别。TBX3缺失对骨髓细胞体外诱导分化成为破骨细胞的能力无显著影响。TBX3可能并非小鼠体内骨量以及破骨细胞分化的主要调控因子，其功能可能被其它T-box蛋白所替代。我们与国外合作的骨质疏松相关研究首次发现细胞内蛋白BCA3与小GTP酶Rac1相互作用可显著上调NFkB信号通路活性。构建破骨细胞特异的BCA3过表达动物模型并研究发现BCA3蛋白对小鼠骨量无显著影响，BCA3蛋白对NFkB信号通路的作用具有高度的细胞特异性。