THE ROLE OF ATROPHIN-2 IN CARTILAGE PATTERNING AND POLARITY IN ZEBRAFISH

描述（由申请人提供）：为了诊断和治疗人类骨骼缺陷，重要的是要了解在发育过程中启动关节软骨冷凝、成熟和重组的分子途径。胚胎中的早期软骨骨骼是成年人大部分骨骨骼的蓝图，包括不同元素的形状和相互连接。我们正在利用斑马鱼的遗传优势来鉴定颅面骨骼发育所必需的基因。颅面软骨和骨骼由神经嵴（NC）细胞形成，不像脊椎或肢体骨骼。特别是在咽部骨骼中，NC细胞获得背腹（D-V）极性，形成通过关节连接到头骨的上下颌。即使在这个阶段，每个软骨都有不同的极性。尽管软骨模式在脊椎动物发育和疾病中具有根本的重要性，但令人惊讶的是，对其潜在的分子控制知之甚少。研究主要集中在软骨成熟和四肢骨替代的机制上，但对软骨元素如何获得其身份或软骨细胞如何在元素内组织以确定其形状知之甚少。在脊椎动物的颌骨中，包括内皮素-1（Edn 1）的信号网络与D-V软骨模式有关。我们最近发现的转录因子Atrophin-2（Atr 2）的斑马鱼突变，与Edn 1突变体类似的关节缺陷，提供了第一次机会来研究Atr 2在调节下颌信号网络中的作用。此外，Atr 2突变体在软骨堆积中产生缺陷，这表明平面细胞极性（PCP）可能具有功能，PCP在许多情况下控制组织极性，但尚未显示在骨骼组织中发挥作用。这项研究的长期目标是了解颅面骨骼中软骨细胞命运决定和极性的细胞和分子基础。目的1和2将检验以下假设：软骨和关节的形成是来自周围组织的Atr 2依赖性信号（例如Edn 1、Bmp、Fgf）的独特组合的结果，这些信号决定了它们的命运。目的3将测试的假设，Atr 2也调节控制细胞极性的骨骼祖细胞之间的相互作用，可能通过一种新的PCP依赖性机制。这些过程可能在成人骨骼中持续存在，并在人类骨骼畸形和疾病中发生改变。

DESCRIPTION (provided by applicant): To diagnose and treat skeletal defects in humans, it is important to know the molecular pathways that initiate cartilage condensation, maturation and reorganization at joints during development. The early cartilaginous skeleton in the embryo serves as a blueprint for much of the bony skeleton of the adult, including the shapes and interconnections of different elements. We are using the genetic advantages of the zebrafish to identify genes essential for development of the craniofacial skeleton. Craniofacial cartilages and bones form from neural crest (NC) cells, unlike the vertebral or limb skeletons. In the pharyngeal skeleton in particular, NC cells acquire a dorsal-ventral (D-V) polarity, forming upper and lower jaws attached to the skull by joints. Even at this stage, each cartilage has a distinct polarity. In spite of the fundamental importance of cartilage patterning in vertebrate development and disease, surprisingly little is known about its underlying molecular control. Research has focused on mechanisms of cartilage maturation and replacement by bone in the limbs, but less is known about how cartilage elements acquire their identities, or how chondrocytes organize within an element to determine its shape. In the vertebrate jaw, a network of signals including Endothelin-1 (Edn1) has been implicated in D-V cartilage patterning. Our recent discovery of a zebrafish mutation in the transcription factor Atrophin-2 (Atr2), with joint defects similar to Edn1 mutants, provides the first opportunity to study the roles of Atr2 in regulating the mandibular signaling network. In addition, Atr2 mutants develop defects in cartilage stacking that suggest a possible function in planar cell polarity (PCP), which controls tissue polarity in many contexts but has not been shown to play a role in skeletal tissues. The long-term goal of this research is to understand the cellular and molecular basis of cartilage cell fate determination and polarity in the craniofacial skeleton. Aims 1 and 2 will test the hypothesis that cartilages and joints form as a result of a unique combination of Atr2-dependent signals (e.g. Edn1, Bmp, Fgf) from surrounding tissues that determine their fates. Aim 3 will test the hypothesis that Atr2 also regulates interactions between skeletal progenitors that control cell polarity, possibly through a novel PCP-dependent mechanism. These processes are likely to persist in the adult skeleton, and to be altered in human malformations and diseases of the skeleton.