Role of p53 in Osteoblast Differentiation

描述(由申请人提供)： 该项目的长期目标是研究P53在成骨细胞分化中的作用，成骨细胞分化是骨形成的核心过程。在我们对骨肉瘤的研究中，我们发现P53的功能缺失占主导地位，而将野生型P53基因替换到这些细胞中不仅会导致生长抑制，而且会诱导成骨细胞分化。我们已经确定了一种与骨骼特异的分化相关基因--骨钙素，它受P53的调控。虽然P53在组织分化中的作用越来越被接受，但它一直很难定义。我们认为，由于P53参与了细胞凋亡和细胞周期停滞等细胞通路，因此它通过分解来自多个来源的输入为分化提供了正确的内部环境。我们发现，在分化过程的后期，P53活性选择性地保持，这与骨特异基因表达上调相一致。因此，拟议的实验旨在了解：a)。成骨细胞分化过程中P53依赖基因表达的性质。 b)。允许维持P53表达的调节类型。c)。P53‘S转录激活的一些骨特异靶点。研究的重点将是：a)。确定在分化过程中调控的P53基因。b)。目的：研究MDM2和p19ARF基因在成骨细胞分化过程中对P53活性的影响。c)。关于P53如何直接调节骨特异性分化相关骨钙素基因和骨形态发生蛋白2(BMP-2)的活性。我们期望所提出的研究将产生有价值的新数据，更多地阐明上述蛋白质的生理作用，并促进我们对成骨细胞分化机制的了解。更好地了解细胞生物学的这一基本方面也可能在涉及骨骼和癌症的疾病中带来额外的好处。阐明肿瘤阻碍细胞分化的机制可能使制定规避它们的策略成为可能。产生的信息将增强我们对p53的理解，并为基因治疗方法扩展到骨肉瘤和其他骨骼疾病(如类风湿性关节炎)患者提供进一步的途径，在这些疾病中，p53突变占主导地位。

DESCRIPTION (provided by applicant): The long-term goal of the project is to investigate the role of p53 in osteoblast differentiation, a process central to bone formation. In our studies with osteosarcomas, we have shown that function al loss of p53 predominates, and replacing the wild type p53 gene in to these cells not only results in suppression of growth, but in the induction of osteoblast differentiation. We have identified a bone specific, differentiation related gene, osteocalcin, to be regulated by p53. While a role for p53 in tissue differentiation is increasingly being accepted, it has been difficult to define. We propose that p53 provides the right internal environment for differentiation by factoring the in put from several sources, due to its involvement in cellular pathways like apoptosis and cell cycle arrest. We have found p53 activity to be selectively maintained late during the differentiation process, coinciding with the upregulation of bone specific gene expression. The proposed experiments are therefore designed to understand: a). The nature of p53-dependent gene expression during osteoblast differentiation. b). The type of regulation that allows the maintenance of p53 expression. c). Some of the bone specific targets of p53's transcription activation. The focus of the research will be: a). To identify the p53-regulated genes that are modulated during differentiation. b). To determine how the mdm2 and p19ARF genes affect p53 activity during osteoblast differentiation. c). On how p53 directly regulates the activity of the bone specific, differentiation related osteocalcin gene, and bone morphogenetic protein 2 (BMP-2). We anticipate that the proposed studies will generate valuable new data, shed more light on the physiological roles of the above proteins, and advance our knowledge of the mechanisms responsible for osteoblast cell differentiation. A better understanding of this basic aspect of cell biology could also potentially lead to additional benefits in diseases involving bone and cancer. Elucidation of the mechanisms whereby tumors block cell differentiation could make possible the development of strategies to circumvent them. The information generated would enhance our understanding of p53 and provide further avenues for gene therapy modalities to be extended to patients with osteosarcomas and other bone disorders such as rheumatoid arthritis, where p53 mutations predominate.