Control of Osteoblast Proliferation and Differentiation

描述(申请人提供)：骨形成是一个受调节和有序的发育过程，需要成骨细胞的生物合成和代谢功能。这个项目自18年前启动以来，促进了我们对调控成骨细胞增殖和分化的细胞和分子机制的理解，包括成骨细胞表型成熟的不同阶段的表征。我们发现Runx2是成骨分化所必需的转录因子，整合了发育信号通路，是一种新的决定细胞命运的表观遗传调节因子。MicroRNAs通过改变mRNAs的水平和翻译潜能来控制基因表达程序。我们在当前时期的主要发现之一是microRNAs在控制成骨细胞谱系-承诺和成熟以及调节骨量的成骨信号通路中的关键作用(Li等人，ProC.娜塔莉。阿卡德。科学，2008；Li等人，J.Biol。化学，2009)。我们的初步数据表明，Runx2可能调节microRNAs的表达，从而减弱骨形成所需的关键生物学途径。因此，我们的中心假设是，microRNAs控制成骨细胞在关键发育阶段的承诺和分化，以调控骨形成，并且这些miR的子集与Runx2有机械联系。因此，我们认为发育中表达的microRNAs可以为治疗骨骼疾病提供一种新的策略。在拟议的研究中，我们将(I)表征microRNAs如何控制成骨细胞表型的发育，(Ii)分析依赖Runx2的microRNAs的功能，以及(Iii)表征在成骨细胞中产生成熟microRNAs缺陷的小鼠的骨骼表型。我们的研究的意义在于定义了microRNA、成骨信号通路和Runx2在控制成骨细胞分化中的机制联系，这将为骨形成的分子基础提供创新性的见解。我们鉴定的对骨合成代谢效应具有限速作用的microRNA的主要影响是，有可能开发基于microRNA的翻译前方法，作为临床应用的一个新维度，以调节患者的骨量。 与公共卫生相关：microRNAs已经成为生物细胞谱系承诺、分化和凋亡的关键调节者，也与许多疾病状态(癌症、纤维化、关节炎)有关。这种最近得到认可的转录后调控水平与正常骨骼发育和转换的关系已经被最少研究过。识别与骨相关的MIR及其调控成骨细胞生长和分化的靶点将为骨疾病的治疗开辟新的途径。

DESCRIPTION (provided by applicant): Bone formation is a regulated and ordered developmental process that requires the biosynthetic and metabolic functions of osteoblasts. This program since its inception 18 years ago has advanced our understanding of cellular and molecular mechanisms that regulate osteoblast proliferation and differentiation, including the characterization of distinct stages of osteoblast phenotype maturation. We identified Runx2 as a transcription factor essential for osteogenic differentiation that integrates developmental signaling pathways and is a novel epigenetic regulator of cell fate determination. MicroRNAs control gene expression programs by altering both the levels and translational potential of mRNAs. One of our major discoveries in the current period is the critical role of microRNAs in controlling osteoblast lineage-commitment and maturation, as well as osteogenic signaling pathways that regulate bone mass (Li et al., Proc. Natl. Acad. Sci., 2008; Li et al, J. Biol. Chem., 2009). Our preliminary data indicate that Runx2 may regulate the expression of microRNAs that attenuate key biological pathways necessary for bone formation. Therefore, our central hypothesis is that microRNAs control commitment and differentiation of osteoblasts at key developmental transitions for regulating bone formation and that a subset of these miRs is mechanistically linked to Runx2. Consequently, we propose that developmentally expressed microRNAs can provide a novel strategy for treating skeletal disorders. In the proposed studies, we will (i) characterize how microRNAs control development of the osteoblast phenotype, (ii) analyze the function of Runx2 dependent microRNAs, and (iii) characterize skeletal phenotypes in mice defective in producing mature microRNAs in osteoblasts. The significance of our studies is the definition of mechanistic linkages among microRNAs, osteogenic signaling pathways and Runx2 in controlling osteoblast differentiation that will provide innovative insight into the molecular basis of bone formation. The principal impact of our identification of microRNAs that are rate-limiting for bone anabolic effects is the potential to develop microRNA-based pre-translational approaches as a novel dimension for clinical applications to modulate bone mass in patients. PUBLIC HEALTH RELEVANCE: MicroRNAs have emerged as key regulators of biological cell lineage commitment and differentiation and apoptosis and are also associated with numerous disease states (cancer, fibrosis, arthritis). This recently appreciated level of post-transcriptional control has been minimally studied in relation to normal bone development and turnover. Identification of bone- related miRs and their targets for control of osteoblast growth and differentiation will lead to novel approaches for treating bone diseases.