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

生物体进化能力的一个关键特征是将它们的整体形态组织成独立变化的单位或模块，这些单元或模块在独立遗传路径的控制下发展。这项拟议的研究使用脊椎动物的牙列来检验这种模块化组织是否适用于合并系统，即由多个结构相似的部分组成的系统。需要检验的具体假设是，已知的鱼类牙列区域独立进化是在不同组基因的控制下发展的。将对斑马鱼(Danio Rerio)和墨西哥斑马鱼(Astianax Micianus)这两个物种进行牙列发育遗传学分析。前者是发育遗传学研究的流行模式系统，仅在咽部拥有牙齿，而后者拥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牙齿发育的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(S)。要检测的基因是已知与哺乳动物牙列发育有关的成纤维细胞生长因子(成纤维细胞生长因子)、HH(刺猬)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，对成纤维细胞生长因子和HH信号的药物抑制的影响，以及(在斑马鱼中)对每个信号通路组成部分突变的形态和基因表达的影响。潜在的结果包括在两种类型的牙齿中使用由不同的启动信号触发的相同的遗传路径，而不是整个路径中存在广泛的差异。通过了解特定区域牙齿丢失的机制，可以进一步了解牙列中的模块化。斑马鱼谱系中口腔牙齿的进化损失将通过比较两个物种口腔区域的基因表达模式来调查。口腔表达差异的基因可能参与了口腔和咽部牙齿的独立进化。拟议研究中将收集的数据将为鳞片和四肢等其他合并系统成员的发展和进化提供机制。

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.