Modularity in the Development and Evolution of the Dentition of Teleost Fishes

0092487StockIt已被假设，一个关键的功能，有助于生物体的能力，以演变是组织的整体形态成独立的变化单位，或模块，发展下的独立遗传途径的控制。拟议的研究使用脊椎动物的齿系，以检查是否这种模块化组织适用于meristic系统，即那些由多个类似构造的部分。有待检验的具体假设是，已知鱼类的牙列区域在不同基因组的控制下独立进化。将在两个物种，斑马鱼（Danio rerio）和墨西哥四（Astyanax mexicanus）中进行齿系发育遗传分析。前一种物种是发育遗传学研究的流行模式系统，仅在咽部区域具有牙齿，而后者同时具有咽部牙齿和口腔边缘的牙齿。该项目的目标是确定口腔和咽部区域牙齿发育遗传控制的模块化程度，并描述斑马鱼谱系在保留咽部牙齿的同时失去口腔牙齿的机制。待检测的基因是已知参与哺乳动物牙列发育的Fgf（成纤维细胞生长因子）、Hh（刺猬蛋白）和Bmp（骨形态发生蛋白）信号通路的成员。将通过比较两个物种内的口腔和咽部区域来研究牙列的模块化遗传控制。这些比较将包括基因表达模式，Fgf和Hh信号传导的药理学抑制的影响，以及（在斑马鱼中）每个信号传导途径的组成部分中的突变的形态和基因表达的后果。潜在的结果包括使用相同的遗传通路触发的单独的启动信号在两种类型的牙齿与存在广泛的差异，在整个pathways.Further洞察模块化的牙列可以通过了解特定区域的牙齿损失的机制。通过比较两个物种口腔区域之间的基因表达模式，研究斑马鱼谱系中口腔牙齿的进化丧失。在口腔表达中表现出差异的基因可能参与了口腔和咽部牙齿的独立进化。在拟议的研究中收集的数据将提出其他分生系统（如鳞片和四肢）成员的发展和进化机制。

0092487StockIt has been hypothesized that a key feature contributing to the capacity of organisms to evolve is the organization of their overall morphology into independently varying units, or modules, that develop under the control of independent genetic pathways. The proposed research uses the vertebrate dentition to examine whether such modular organization applies to meristic systems, i.e. those composed of multiple similarly-constructed parts. The specific hypothesis to be tested is that regions of the dentition of fishes known to evolve independently develop under the control of different sets of genes. Developmental genetic analyses of the dentition will be carried out in two species, the zebrafish (Danio rerio), and the Mexican tetra (Astyanax mexicanus). The former species, a popular model system for developmental genetic studies, possesses teeth only in the pharyngeal region, while the latter possesses both pharyngeal teeth and teeth lining the margins of the oral cavity. The objectives of the project are to determine the extent of modularity in the genetic control of tooth development in oral and pharyngeal regions, and to characterize the mechanism(s) by which the zebrafish lineage has lost oral teeth while retaining pharyngeal teeth. The genes to be examined are members of the Fgf (fibroblast growth factor), Hh (hedgehog), and Bmp (bone morphogenetic protein) signaling pathways known to be involved in the development of the mammalian dentition. Modular genetic control of the the dentition will be investigated by comparisons of oral and pharyngeal regions within both species. These comparisons will include gene expression patterns, the effects of pharmacological inhibition of Fgf and Hh signaling, and (in the zebrafish) the consequences for morphology and gene expression of mutations in components of each signaling pathway. Potential outcomes include the use of identical genetic pathways triggered by separate initiation signals in the two types of teeth versus the existence of extensive differences throughout the pathways.Further insight on modularity in the dentition can be gained by an understanding of the mechanisms of region-specific tooth loss. Evolutionary loss of oral teeth in the zebrafish lineage will be investigated by comparison of gene expression patterns between the oral regions of both species. Genes exhibiting differences in oral expression are likely to have been involved in the independent evolution of oral and pharyngeal teeth. The data to be collected in the proposed research will suggest mechanisms for the development and evolution of members of other meristic systems such as scales and limbs.