CONSTITUTIVELY ACTIVE PTH/PTHRP RECEPTORS IN OSTEOBLAST

骨与肾是PTH的主要靶器官。是 已知PTH增加骨转换，但不清楚为什么在体内， 具有合成代谢作用时，它是管理间歇，而其 当以连续的方式给予时，分解代谢作用占优势。 PTH 增强骨细胞活性，但其是否 对破骨细胞的作用仅通过成骨细胞介导，或者 他们也是直接的。成骨细胞是PTH作用的主要靶点。 然而，在成骨细胞谱系中， 成骨细胞和成熟的成骨细胞-介导的 PTH在体内的各种作用是一个悬而未决的问题。 也是未知数 PTHrP如何影响成骨细胞功能， 软骨细胞分化最后，克隆的PTH/PTHrP受体是 能够激活至少两种不同的信号通路，腺苷酸 环化酶和磷脂酶C。然而，其相对重要性 介导PTH对成骨细胞的作用需要澄清。最近 PTH/PTHrP受体中两种不同突变的鉴定 在詹森干骺端软骨发育不良（JMC）患者中， 配体非依赖性结构性cAMP积累，给了我们一个强大的 用于通过实验探索至少上述部分内容的工具 问题. 我们建议开发转基因小鼠， PTH/PTHrP受体将在两种不同的细胞因子的控制下表达。 发起人。α 1（I）胶原蛋白和骨钙素促进剂，以使其 在较不成熟和/或较成熟成骨细胞中的靶向表达 具体目标（一）。对这些动物的分析将有助于 以确定和区分这些细胞在介导 对PTH和PTHrP的反应（特异性目的II）。我们还提议交配 这些转基因小鼠和选择性缺乏PTH基因的小鼠， 确定PTH对成骨细胞功能和成熟的影响， 依赖于cAMP途径的PTH/PTHrP受体活化 （具体目标三）。最后，我们将上述转基因小鼠交配， 将小鼠与对胶原酶-3切割具有抗性的动物进行比较， 证实胶原酶-3诱导对骨的重要性 PTH诱导的重塑过程，无论是在发育过程中还是在成人中 （四）具体目标。

Bone is, together with kidney, the major target organ of PTH. It is known that PTH increases bone turnover, but it is obscure why in vivo it has an anabolic effect when it is administered intermittently, while its catabolic action prevails when it is given in a continuous fashion. PTH augments osteoclastic activity, but it is controversial whether its effects on osteoclasts are only mediated through osteoblasts, or whether they are also direct. Osteoblasts are the major target of PTH action. Which cells, however, in the osteoblast lineage- a spectrum from osteoprogenitors to pre-osteoblasts and mature osteoblasts - mediate the various actions of PTH in vivo is an open question. It is also unknown how PTHrP influenced osteoblast function independently of its role on chondrocyte differentiation. Finally, the cloned PTH/PTHrP receptor is able to activate at least two different signaling pathways, adenylate cyclase and phospholipase C. However, their relative importance in mediating the PTH effect on osteoblasts needs to be clarified. Recently the identification of two different mutations in the PTH/PTHrP receptor in patients with Jansen's metaphyseal chondrodysplasia (JMC), that lead to ligand-independent constitutive cAMP accumulation, gave us a powerful tool to explore experimentally at least some of the above mentioned questions. We propose to develop transgenic mice in which mutant PTH/PTHrP receptors will be expressed under the control of two different promoters. alpha1(I) collagen and osteocalcin promoters, to allow their targeted expression in less mature and/or more mature osteoblasts respectively (Specific Aim I). The analysis of these animals will help to determine and distinguish the roles of these cells in mediating the response to PTH and PTHrP (Specific Aim II). We also propose to mate these transgenic mice with the ones that selectively lack the PTH gene, to identify PTH effects on osteoblast function and maturation that are dependent on the PTH/PTHrP receptor activation of the cAMP pathway (Specific Aim III). Lastly, we will mate the above described transgenic mice with the animals that are resistant to collagenase-3 cleavage to confirm the importance of collagenase-3 induction for the bone remodeling process induced by PTH, both during development and in adult life (Specific Aim IV).