Molecular Control of Bone Formation

摘要 我们提议的研究将调查表观遗传酶调节血统的中心假设- 骨形成细胞在体内的定位和成熟。我们的研究将为骨骼的新策略提供信息 旨在降低骨折风险的合成代谢疗法。目前的治疗方法有主要的临床副作用和 病人限制。然而，随着美国人口老龄化，迫切需要 开发促进骨积累的新策略。此外，还有一系列短期合成代谢 将受益于基于新机制的应用(例如脊柱融合、辐射导致的骨丢失) 接近了。拟议的工作将提供(I)利用表观遗传药物促进 翻译前环境中的骨积累，但也是(Ii)对染色质作用的基本见解 异染色质在控制骨形成中的作用。 目的1评估组蛋白基因的有条件消融的体内骨刺激效应 甲基转移酶EZH2在出生后发育和骨骼成熟小鼠中的作用 基因在间充质干细胞或成骨细胞中缺失。这些研究将揭示基因缺失是否会导致 EZH2刺激骨积累，具有骨保护作用(在去卵巢的小鼠雌激素耗尽后)，和/或 加速骨骼愈合。这些基因研究将跟进我们的初步数据，表明 具有已建立的安全性特征的药物抑制剂(例如，EZH2抑制剂GSK126)可用于 体内促进骨积累，体外促进成骨细胞分化。 目的2研究EZH2失活对骨刺激作用的分子基础。vbl.使用 基因组学方法(芯片序列和RNA序列)，我们将定义和功能测试信号分子和 对EZH2抑制反应的基因调控因子。我们还将专门调查有吸引力的 抑制EZH2通过增强内源性旁分泌启动持续性骨合成反应的模型 成骨配体(如BMP、WNT和PTH)的信号转导。我们将特别关注研究 我们新观察到GSK126和BMP2在成骨细胞成熟过程中协同作用的分子基础。 我们的发现为考虑表观遗传学提供了遗传学支持，具有重要的临床意义。 促进新骨形成的药物。这些研究的概念创新将通过分子获得 分析EZH2的表观遗传调节作用，它允许定义早期机械事件， 控制成骨分化和成骨细胞成熟。

ABSTRACT Our proposed studies will investigate the central hypothesis that epigenetic enzymes regulate lineage- commitment and maturation of bone forming cells in vivo. Our studies will inform new strategies for bone anabolic therapies aimed at reducing fracture risk. Current therapies have major clinical side-effects and patient restrictions. Yet, with the aging demographics of the US population, there is a significant urgency to develop new strategies that promote bone accrual. In addition, there are a range of short term anabolic applications (e.g., spine fusion, radiation induced bone loss) that would benefit from new mechanism-based approaches. The proposed work will provide (i) proof of concept for leveraging epigenetic drugs to promote bone accrual in a pre-translational setting, but also (ii) fundamental insights into the role of chromatin heterochromatinization in controlling bone formation. Aim 1 will assess the in vivo bone stimulatory effects of conditional ablation of the gene for histone methyl transferase EZH2 during post-natal development and in skeletally mature mice in which the EZH2 gene is deleted in mesenchymal stem cells or osteoblasts. These studies will reveal whether genetic loss of EZH2 stimulates bone accrual, is osteoprotective (after estrogen-depletion in ovariectomized mice), and/or accelerates bone healing. These genetic studies will follow-up on our preliminary data indicating that pharmacological inhibitors with established safety profiles (e.g., EZH2 inhibitor GSK126) can be used to promote bone accrual in vivo and osteoblast differentiation in vitro. Aim 2 will examine the molecular basis for the bone stimulatory effects of EZH2 inactivation. Using genomics approaches (ChIP-seq and RNA-seq), we will define and functionally test signaling molecules and gene regulatory factors that respond to EZH2 inhibition. We will also specifically investigate the attractive model that EZH2 inhibition initiates a sustained bone anabolic response by enhancing endogenous paracrine signaling of osteogenic ligands (e.g., BMP, WNT and PTH). We will focus specifically on examining the molecular basis for our new observation that GSK126 and BMP2 synergize in osteoblast maturation. Our findings have important clinical ramifications by generating genetic support for considering epigenetic drugs in promoting new bone formation. Conceptual innovation of these studies will be obtained by molecular analysis of the epigenetic regulatory role for EZH2 which permits definition of early mechanistic events that control osteogenic differentiation and osteoblast maturation.