Effects of osteocyte specific Gs alpha signaling on bone mass and hematopoiesis

描述（由申请人提供）：骨细胞占所有骨细胞的90%以上，但对其功能或调节其活性的全身激素的参与知之甚少。最近的研究支持骨细胞发挥主要的“机械感觉”作用的理论。骨细胞是如何准确地感知施加在骨骼上的机械力，然后将这种机械刺激转化为生物功能的，目前还不完全清楚。几种激素，特别是前列腺素E2 （PGE2）和甲状旁腺激素（PTH）参与了这一过程。本研究将探讨骨细胞中的Gsa信号对于骨细胞的机械转导和骨稳态至关重要的假设。此外，我们的初步数据显示，骨细胞中缺乏gsa信号会导致造血异常。本研究的第一个目的是验证骨细胞中的gsa信号对于骨获取和骨骼稳态至关重要的假设。第二个目的将研究骨细胞中gsa介导的信号传导是机械转导的重要调节因子的假设。最后，在目的III中，我们将研究Gsa在造血中的作用。为了解决这些问题，已经产生了骨细胞中特异性消融Gsa表达的小鼠。为了限制Gsa对骨细胞的侵蚀，我们使用已知在骨细胞中特异性表达的牙本质基质蛋白-1 （DMP-1）的10Kb上游启动子来驱动Gsa重组酶，在小鼠中，Gsa的外显子1被Lox-P位点所修饰。该动物模型将有助于进一步了解Gsa对骨骼和造血系统的作用，并可指导新型治疗剂的开发。本文提出的研究将扩展目前对骨细胞中gsa信号传导的认识，并将研究这些细胞中gsa依赖通路在多大程度上参与正常骨骼发育、造血和矿物质离子稳态。在这样做的过程中，他们承诺显著扩大对骨细胞和骨生物学的理解。我们希望验证的假设是，骨细胞中的Gsa信号直接影响骨稳态和机械感觉，并直接或间接控制髓细胞的发育和造血。如果我们的假设成立，这将是骨细胞第一次被证明调节造血功能。

DESCRIPTION (provided by applicant): Osteocytes comprise over 90% of all bone cells, yet little is known of their function(s) or of the involvement of systemic hormones in regulating their activity. Recent studies support the theory that osteocytes play a major "mechanosensory" role. How exactly the osteocyte can sense the mechanical forces applied to the bone and then transform this mechanical stimulus into a biological function remains incompletely understood. Several hormones, particularly prostaglandin E2 (PGE2) and parathyroid hormone (PTH) had been implicated in this process. This proposal will investigate the hypothesis that Gsa- signaling in osteocytes is critical for proper mechano-transduction and bone homeostasis. Moreover, our initial data revealed that lack of Gsa-signaling in osteocytes induce hematopoietic abnormalities. The first aim of this proposal will test the hypothesis that Gsa-signaling in osteocytes is important for proper bone acquisition and skeletal homeostasis. The second aim will investigate the hypothesis that Gsa-mediated signaling in osteocyte is an important regulator of mechano-transduction. Lastly, in aim III we will investigate the role of Gsa in hematopoiesis. To address these questions, mice in which Gsa expression is specifically ablated in osteocytes have been generated. To restrict ablation of Gsa to osteocytes, we used the 10Kb upstream promoter of Dentin Matrix Protein-1 (DMP-1), known to be expressed specifically in osteocytes, to drive the Cre-recombinase in mice in which Exon1 of Gnas is flanked by Lox-P sites. This animal model will enable enhanced understanding of Gsa action on bone and on the hematopoietic system and could direct the development of novel therapeutic agents. The studies proposed here will expand the current knowledge on Gsa-signaling in osteocytes and will investigate the extent to which Gsa-dependent pathways in these cells is involved in normal skeletal development, hematopoiesis and mineral-ion homeostasis. In so doing, they promise to significantly expand understanding of osteocyte and bone biology. The hypothesis that we wish to test is that signaling via Gsa in osteocytes directly affects bone homeostasis and mechanosensation and directly, or indirectly controls myeloid cells development and hematopoiesis. If our hypothesis holds true it will be the first time that osteocytes are shown to regulate hematopoiesis.