Control of Osteoblast Proliferation and Differentiation

描述（由申请人提供）：骨形成是一个受调控和有序的发育过程，需要成骨细胞的生物合成和代谢功能。自18年前成立以来，该计划已经推进了我们对调节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。我们确定Runx 2作为成骨分化所必需的转录因子，整合了发育信号通路，是一种新的细胞命运决定的表观遗传调节因子。MicroRNA通过改变mRNA的水平和翻译潜力来控制基因表达程序。我们在当前时期的主要发现之一是微RNA在控制成骨细胞谱系定型和成熟以及调节骨量的成骨信号传导途径中的关键作用（Li等人，Proc. Natl. Acad.科学，2008; Li等人，J. Biol. Chem.，2009年）。我们的初步数据表明，Runx 2可以调节microRNA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microRNA控制成骨细胞在关键发育过渡期的定型和分化，以调节骨形成，并且这些miR的子集与Runx 2机制相关。 因此，我们认为发育中表达的microRNA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microRNA如何控制成骨细胞表型的发育，（ii）分析Runx 2依赖性microRNA的功能，（iii）表征成骨细胞中产生成熟microRNA缺陷的小鼠的骨骼表型。我们的研究的意义在于定义microRNA、成骨信号通路和Runx 2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。我们鉴定对骨合成代谢作用具有限速作用的microRNA的主要影响是开发基于microRNA的翻译前方法作为临床应用的新维度以调节患者骨量的潜力。 公共卫生相关性：MicroRNA已经成为生物细胞谱系定型和分化以及凋亡的关键调节因子，并且还与许多疾病状态（癌症、纤维化、关节炎）相关。这种最近受到重视的转录后控制水平与正常骨发育和营业额的关系研究很少。骨相关miR及其控制成骨细胞生长和分化的靶点的鉴定将导致治疗骨疾病的新方法。

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.