Mechanisms of Synovial Joint Formation

描述（由申请人提供）：滑膜关节对骨骼功能至关重要，但我们仍然对它们在胎儿生命中如何形成一无所知。在肢体中，关节发育开始于在未来关节部位出现间充质间带。间带祖细胞被认为产生包括关节软骨在内的组织并参与关节形态发生，但尚不清楚细胞如何执行这些关键任务。信号传导蛋白GDF-5和Wnt-14在早期间区强烈表达。发现GDF-5作为生长和区间决定因子，而Wnt-14作为区间/早期关节基因的上游调节因子，包括GDF-5本身、Chordin和CD-44。在初步工作中，我们首次表明：Wnt-14和GDF-5在间区形成过程中以不同的模式表达;关节周围间充质细胞迁移到新生间区; GDF-5表达在关节形态发生过程中仅限于凸面; Wnt-14信号传导涉及b-连环蛋白。我们的主要假设是：（ii）GDF-5和Wnt-14在区域间和关节形成和形态发生期间具有不同但相互关联的作用。我们的目标是建立区间细胞的起源和命运图，确定GDF-5和Wnt-14的作用和作用机制，并建立条件性Wnt-14消融小鼠和评估后果。我们将使用细胞追踪-追踪程序，包括与可用的GDF-5-Cre小鼠交配的ROSA报告小鼠;嵌合体显微外科方法;以及鸡和小鼠足动物（爪）上的Wnt-14和GDF-5获得和丧失功能的方法，包括从可用的GDF-5缺失短足症小鼠和b-连环蛋白依赖性轴蛋白-2启动子报告小鼠中分离的那些。该项目将产生关于联合组建机制的基本信息。这些结果将是非常宝贵的，在构思新的，定向的和具体的治疗，以修复和恢复关节功能障碍常见的老年人和其他受影响的患者。

DESCRIPTION (provided by applicant): Synovial joints are critical for skeletal function, but we remain surprisingly ignorant about how they actually form during fetal life. In the limb, joint development starts with appearance of a mesenchymal interzone at future joint sites. Interzone progenitor cells are thought to give rise to tissues including articular cartilage and participate in joint morphogenesis, but it is not clear how the cells perform these critical tasks. The signaling proteins GDF-5 and Wnt-14 are strongly expressed by early interzone. GDF-5 was found to act as a growth and interzone determination factor, while Wnt-14 acted as an upstream regulator of interzone/early joint genes, including GDF-5 itself, Chordin and CD-44. In preliminary work we show for the first time that: Wnt-14 and GDF-5 are expressed in distinct patterns during interzone formation; peri-joint mesenchymal cells migrate into nascent interzone; GDF-5 expression becomes restricted to convex side during joint morphogenesis; and Wnt-14 signaling involves b-catenin. Our central hypotheses are: (i) interzone is made of progenitor cells derived from peri-joint sites; and (ii) GDF-5 and Wnt-14 have distinct, but interrelated roles during interzone and joint formation and morphogenesis. Our aims are to establish origin and fate maps of interzone cells, determine GDF-5 and Wnt-14 roles and mechanisms of action, and create conditionally Wnt-14-ablated mice and assess consequences. We will use cell tracing-tracking procedures, including ROSA reporter mice mated with available GDF-5-Cre mice; chimeric-microsurgical approaches; and Wnt-14 and GDF-5 gain- and loss-of-function approaches on chick and mouse autopods (paws), including those isolated from available GDF-5-null brachypodism mice and b-catenin-dependent axin-2 promoter reporter mice. The project will generate fundamental information on mechanisms of joint formation. The results will be invaluable in conceiving novel, directed and specific therapies to repair and restore malfunctioning joints common to aging individuals and otherwise affected patients.