The Role of Dlx Genes in the Development and Evolution of the Teleost Fish Dentition

Dlx 基因在硬骨鱼牙列发育和进化中的作用

• 批准号: 0446720
• 负责人: David Stock
• 金额: --
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2010-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0446720&HistoricalAwards=false
• 关键词: Role; Dlx; Genes; Development; Evolution

PROJECT SUMMARY Whether macroevolutionary patterns result from natural selection or developmental constraints has long been debated. The proposed research seeks to explain in terms of such external or internal forces an evolutionary trend toward tooth reduction in vertebrates. Loss of oral teeth in cypriniform fishes (e.g. minnows) serves as a model of this trend. No member of the group has regained oral teeth, despite diverse feeding modes and retention of throat teeth, suggesting tooth loss as a constraint on evolution. Characterizing the developmental mechanism of this loss will test the constraint hypothesis; identifying a simple, experimentally-reversible mechanism would argue against it. Previous comparisons of gene expression in the cypriniform zebrafish (Danio rerio) and related groups with oral teeth identified an association between absence of teeth and of Dlx2 transcription factor expression. This result will be extended to further characterize modifications of developmental genetic pathways resulting in cypriniform tooth loss. Objectives are to 1) identify the mechanism of Dlx expression evolution, 2) identify consequences of loss and gain of Dlx function, 3) investigate Fibroblast growth factor (Fgf) signaling pathways as potential causes of loss of Dlx expression and oral teeth, and 4) identify any changes in expression of additional Dlx family members associated with tooth loss and evolution of gene family number. The primary species to be employed are the zebrafish and the Japanese medaka (Oryzias latipes), the latter of which retains oral teeth. Transgenic approaches will be used to compare regulation of Dlx2 gene expression in the two species and to misexpress native or modified Dlx and Fgf proteins. Expression of the entire complement of Dlx genes (some of which remain to be cloned) will be examined in the zebrafish, medaka and Mexican tetra (Astyanax mexicanus). These species exhibit differences in dentition and probably in the number of Dlx genes present in their genomes as well. Characterization of the mechanism of cypriniform oral tooth loss will allow comparison with other instances of vertebrate dental reduction, in addition to elucidating fundamental mechanisms of tooth development.Transgenic lines and constructs generated will be valuable for studying the role of Dlx and Fgf genes in the development of other structures. The project will have significant educational value as well. Results and materials will be incorporated into an existing course in Evolutionary Developmental Biology, while several undergraduate students (recruited through universty programs), two graduate students, and a post-doctoral researcher will receive research training while executing the project.

宏观进化模式是否是自然选择或发育限制的结果长期以来一直存在争议。这项拟议中的研究试图用这种外力或内力来解释脊椎动物牙齿减少的进化趋势。鲤科鱼类（如小鱼）的口齿缺失就是这种趋势的一个典型。尽管有不同的进食方式和保留喉齿，但没有一个群体的成员重新获得了口腔牙齿，这表明牙齿缺失是进化的一个限制。表征这种损失的发展机制将测试约束假说，确定一个简单的，实验可逆的机制会反对it.Previous比较的基因表达的cypriniform斑马鱼（斑马鱼）和相关群体与口腔牙齿之间的关联确定的牙齿和Dlx 2转录因子表达的情况。这一结果将被扩展到进一步表征修饰的发育遗传途径，导致鲤形牙缺失。目的是1）鉴定Dlx表达进化的机制，2）鉴定Dlx功能丧失和获得的后果，3）研究成纤维细胞生长因子（FGF）信号传导途径作为Dlx表达和口腔牙齿丧失的潜在原因，以及4）鉴定与牙齿丧失和基因家族数量进化相关的其他Dlx家族成员的表达的任何变化。主要使用的物种是斑马鱼和日本青鳉（Oryzias latipes），后者保留了口腔牙齿。转基因方法将用于比较两个物种中Dlx 2基因表达的调节，并错误表达天然或修饰的Dlx和FGF蛋白。将在斑马鱼、青鳉和墨西哥四鱼（Astyanax mexicanus）中检查Dlx基因（其中一些仍待克隆）的整个补体的表达。这些物种在齿列上表现出差异，并且可能在其基因组中存在的Dlx基因的数量上也表现出差异。鲤形口牙缺失的机制的表征将允许与其他脊椎动物牙齿减少的情况下进行比较，除了阐明牙齿发育的基本机制，产生的转基因株系和构建体将是有价值的，用于研究Dlx和Fgf基因在其他结构的发展中的作用。该项目也将具有重要的教育价值。结果和材料将被纳入进化发育生物学的现有课程，而几名本科生（通过大学课程招募），两名研究生和一名博士后研究员将在执行该项目时接受研究培训。