Genetic and cellular analysis of zebrafish fin development.

我的研究项目包括鳍和肢体发育的比较分析，以及可能导致四足动物四肢从成对鳍（胸鳍、骨盆鳍）进化的分子机制。在发育早期，早期胸鳍芽与肢芽有许多相似之处，但鳍的发育迅速分化，开始于：1)鳍褶的形成；2)褶皱间充质细胞迁移；3)放线菌的形成，这是一种刚性纤维，作为间充质细胞迁移的支架，并作为生长鳍褶的骨骼支撑。这些迁移的间充质细胞（MMCs）在幼鳍和鳍的形成中起着重要的作用，但它们的确切作用尚不完全清楚。这些间充质干细胞不存在于发育中的肢体芽中，这表明这些细胞在四足动物物种中已经丢失或形成了不同的组织。我们最近发现了两个基因调控区域，2Pepi和m-Inta11，它们在斑马鱼胚胎鳍形成时出现的mmc中活跃。2Pepi在MMCs群体中负责actitinodin 1（和1）的表达。And1是鱼类特有的基因，编码放线菌毛体的结构成分；在进化过程中，和基因家族已经从四足动物基因组中丢失。在另一项研究中，我们也发现，切除表达m-Inta11的MMCs会损害早期鳍发育。我们认为MMC的迁移和功能取决于放线菌的正确形成和维持。我们认为这两个过程都是由5'hoxa/hoxd基因的表达介导的。在未来的五年里，我的研究计划将整合我们之前工作的数据和试剂，研究MMCs的作用及其与放线菌的关系，以更好地了解它们对鳍发育的贡献。这个项目将使我们更好地了解鳍的发育，并更好地了解鳍到四肢的转变。更具体地说，我提出以下4个目标：1)使用细胞谱系追踪方法来确定mmc特定亚群的命运。2)研究消融表达和1的MMCs对鳍发育的长期影响。3)研究放线菌形成的遗传破坏对MMCs的影响及其对鳍发育的影响。4)检测5'hoxa/hoxd对和1间质表达的调控。研究MMCs的作用和命运，包括它们对放线菌、鳍折叠和射线发育的贡献，使我们有机会更好地了解鳍发育的机制，并更好地了解鳍到肢体转变背后的形态变化。此外，了解和1和5'HoxA/D蛋白之间的调控联系可以揭示调控变化如何导致四足动物基因组中放线素基因的缺失。

My research program involves the comparative analysis of fin and limb development, and the molecular mechanisms that may have contributed to the evolution of tetrapod limbs from paired fins (pectoral, pelvic). During early development, the early pectoral fin bud shows a lot of similarity with the limb bud but fin development quickly diverges starting with: 1) the formation of a fin fold; 2) migration of mesenchymal cells in the fold; 3) formation of actinotrichia, rigid fibers that act as a scaffold for mesenchymal cell migration and as a skeletal support for the growing fin fold. These migrating mesenchymal cells (named hereafter MMCs) play a fundamental role in the formation of the larval fin and the fin rays, however their exact role is not fully understood. Such MMCs are not present in developing limb buds suggesting that these cells have been lost or contribute to different tissues in tetrapod species. We recently characterized two gene regulatory regions, 2Pepi and m-Inta11 that are active in MMCs arising at the onset of fin fold formation in zebrafish embryonic fins. 2Pepi is responsible for actinodin 1 (and1) expression in a population of MMCs. And1 is a fish-specific gene that encodes for structural components of actinotrichia; the and gene family has been lost from the tetrapod genomes during evolution. In another study, we also showed that ablation of the m-Inta11 expressing MMCs impairs early fin development. We think MMC migration and function depends on the proper formation and maintenance of actinotrichia. We propose both of these processes are mediated by the expression of 5'hoxa/hoxd genes.In the coming five years, my research program will integrate data and reagents from our previous work to investigate the role of MMCs and their relationship to the actinotrichia to better understand their contribution to fin development. This project will allow us to better understand fin development and provide a better insight into the fin-to-limb transition. More specifically, I propose the following 4 aims:1) to use a cell lineage tracing approach to determine the fate of specific subsets of MMCs. 2) to investigate the long-term effects of the ablation of the and1-expressing MMCs on fin development. 3) to examine the effects of the genetic disruption of actinotrichia formation on MMCs and resulting consequences on fin development. 4) to examine the 5'hoxa/hoxd regulation of and1 mesenchymal expression. Investigating the role and fate of the MMCs, including their contributions to actinotrichia, fin fold, and ray development gives us an opportunity to better understand the mechanisms of fin development and provides a better insight into morphological changes underlying the fin-to-limb transition. In addition, understanding the regulatory link between and1 and 5'HoxA/D proteins could shed light on how regulatory changes contributed to the loss of the actinodin genes from the tetrapod genome.