GENE EXPRESSION PATTERNS IN OSTEOCYTES IN RESPONSE TO LOAD

现在已经知道，骨骼对机械负荷适应性的小变化可以导致大的变化 骨骼的抗折性。骨细胞被认为是骨接受的机械感觉细胞。 这些生理信号和反应以调节其局部微环境和 在全球范围内控制骨骼选择性区域的骨形成和骨吸收。牙本质基质蛋白1， DMP1和基质细胞外磷酸糖蛋白(MEPE)在骨细胞和 对机械负荷作出反应。这两种蛋白都高度定位于骨细胞的小管和陷窝中， DMP1主要分布在小管壁上。我们的目标是利用这两个基因作为 代表骨细胞选择基因对机械应变的反应以识别分子信号 导致骨骼特性变化的机制。我们的假设是特定的骨细胞选择性 在DMP1和MEPE的启动子中存在机械响应的增强子区域，它们是 受特定转录家族途径控制，对菌株做出反应。为了检验这一假说，有三个 具体目的：1.确定DMP1与MEPE基因的关系 活体机械加载应变场分析的表达模式。具体目标2.确定 不同应变水平和基因水平与小鼠尺骨和股骨骨细胞变形的关系 激活DMP1和MEPE顺式调节区。具体目标3.确定顺式监管 在骨细胞中控制选择性负荷反应的DMP1和MEPE基因的区域。这 该项目的独特之处在于，DMP1和MEPE基因的表达将与体内的宏观菌株相关 并在体外发生局部细胞变形。这些基因及其相应的顺式调控区域与 记者将作为不同加载条件下骨细胞反应性的灵敏读数 不同的遗传背景。这个项目将致力于理解顺式监管系统 DMP1和MEPE基因对骨细胞的选择性和对转录因子的识别 负责机械装载的选择性和响应性。该项目的目标将是 使用细胞模型来确定分子机制，使用动物模型进行体内验证， 结合工程原理，结合分子和系统生物学方法。 提高疲劳抗力是防止断裂的主要手段。定位骨细胞基因和 选择性地对负荷作出反应的通路将提供对预防或治疗重要的信息 骨病如废用性骨质疏松症、绝经后骨质疏松症等病理性 骨质流失的情况。

It is now known that small changes in bone adaption to mechanical load can lead to large changes in skeletal resistance to fracture. Osteocytes are believed to be the mechanosensory cells of bone receiving these physiological signals and responding in a manner to regulate their local microenvironment and to globally control bone formation and bone resorption in selective regions of bone. Dentin Matrix Protein 1, DMP1, and Matrix Extracellular Phosphoglycoprotein, MEPE, are highly expressed in osteocytes and respond to mechanical load. Both proteins are highly localized in the canaliculi and lacunae of osteocytes, with DMP1 found predominately on the canalicular walls. Our goal is to use these two genes as representative of osteocyte selective genes responsive to mechanical strain to identify molecular signalling mechanisms responsible for changes in bone properties. Our hypothesis is that specific osteocyte selective and mechanically responsive enhancer regions exist in the promoters of DMP1 and MEPE that are controlled by specific transcription family pathways in response to strain. To test this hypothesis three specific aims are proposed: Specific Aim 1. Determine the relationship between DMP1 and MEPE gene expression patterns with strain field analysis upon mechanical loading in vivo. Specific Aim 2. Determine the relationship of osteocyte deformation in the mouse ulna and femur to different levels of strain and gene activation of the DMP1 and MEPE cis-regulatory regions. Specific Aim 3. Determine the cis-regulatory regions of the DMP1 and MEPE genes that control the response to loading selectively in osteocytes. This project is unique in that DMP1 and MEPE gene expression will be correlated with macroscopic strain in vivo and with local cell deformation ex vivo. These genes and their appropriate cis-regulatory regions linked to reporters will serve as sensitive read-outs of osteocyte responsiveness in different loading conditions in different genetic backgrounds. This project will be devoted to understanding the cis-regulatory systems of both the DMP1 and MEPE genes in terms of their osteocyte selectivity and to identifying transcription factors responsible for this selectivity and responsiveness to mechanical loading. The goals of this project will be accomplished using cell models to identify molecular mechanisms, animal models for in vivo validation, together with engineering principles, combined with a molecular and a systems biology approach. Increased fatigue resistance is a major means to prevent fracture. Mapping osteocyte genes and pathways that are selectively responsive to load will provide information important to prevention or treatment of bone disease such as disuse osteoporosis, post menopausal osteoporosis and other pathological conditions of bone loss.