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

描述（申请人提供）：骨细胞占所有骨细胞的90%以上，但对其功能或全身激素参与调节其活性的情况知之甚少。最近的研究支持骨细胞发挥主要的“机械感觉”作用的理论。骨细胞如何准确地感受到施加在骨骼上的机械力，然后将这种机械刺激转化为生物学功能仍然没有完全了解。几种激素，特别是前列腺素E2（PGE 2）和甲状旁腺激素（PTH）参与了这一过程。该提议将研究骨细胞中的Gsa信号传导对于适当的机械转导和骨稳态是至关重要的这一假设。此外，我们的初步数据显示，缺乏Gsa信号在骨细胞诱导造血异常。本提案的第一个目的是测试骨细胞中的Gsa信号传导对于适当的骨获得和骨骼动态平衡很重要的假设。第二个目的是研究骨细胞中Gsa介导的信号转导是机械力信号转导的重要调节因子的假说。最后，在目标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Gsa表达在骨细胞中特异性消融的小鼠。为了将Gsa的消融限制在骨细胞，我们使用了已知在骨细胞中特异性表达的牙本质基质蛋白-1（Dentin Matrix Protein-1，DNT-1）的10 Kb上游启动子来驱动小鼠中的Cre重组酶，其中Gnas的外显子1侧接Lox-P位点。这种动物模型将能够增强对Gsa对骨和造血系统作用的理解，并可指导新型治疗剂的开发。这里提出的研究将扩大目前的知识GSA信号在骨细胞，并将调查在何种程度上GSA依赖的途径在这些细胞参与正常的骨骼发育，造血和矿物质离子稳态。通过这样做，他们有望大大扩展对骨细胞和骨生物学的理解。我们希望测试的假设是，通过Gsa在骨细胞中的信号传导直接影响骨稳态和机械感觉，并直接或间接控制骨髓细胞发育和造血。如果我们的假设成立，这将是第一次骨细胞被证明可以调节造血。

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.