Genetic and cellular analysis of zebrafish fin development.

我的研究项目涉及鳍和肢体发育的比较分析，以及可能有助于四足动物肢体从成对鳍(胸部、骨盆)进化的分子机制。在早期发育过程中，胸鳍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)鳍褶中间充质细胞的迁移；3)放线毛的形成，这是一种坚硬的纤维，作为间充质细胞迁移的支架和不断生长的鳍褶的骨骼支撑。这些迁移的间充质细胞(以下简称MMCs)在幼虫鳍和鳍条的形成中起着基础性的作用，但它们的确切作用尚不完全清楚。这种MMCs在发育中的肢芽中不存在，这表明这些细胞已经丢失，或者在四足动物的不同组织中发挥了作用。 我们最近鉴定了两个基因调控区，2Pepi和m-Inta11，它们在斑马鱼胚胎鳍形成鳍折叠开始时产生的MMCs中活跃。 2Pepi负责在一组MMC中表达放线蛋白1(和1)。And1是一种鱼类特有的基因，编码放线菌的结构成分；和基因家族在进化过程中从四足动物基因组中丢失。在另一项研究中，我们还发现，去除表达m-Inta11的MMCs会损害早期鳍的发育。我们认为MMC的迁移和功能依赖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基因的表达所介导的。 在接下来的五年里，我的研究计划将整合我们以前工作中的数据和试剂，以调查MMCs的作用及其与放线菌的关系，以更好地了解它们对FIN发展的贡献。该项目将使我们能够更好地了解鳍的发展，并对鳍到肢体的过渡提供更好的洞察。 更具体地说，我提出了以下4个目标： 1)使用细胞谱系追踪方法来确定特定的MMC亚群的命运。 2)研究消融And-1表达的MMCs对FIN发育的长期影响。 3)研究放线菌形成的遗传干扰对MMCs的影响及其对鳍发育的影响。 4)检测5‘HoxA/Hoxd对间充质细胞表达的调控。 研究MMCs的作用和命运，包括它们在放线菌、鳍折和射线发育中的贡献，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的形态变化。此外，了解1和5‘HoxA/D蛋白之间的调控联系可以阐明调控变化如何导致四足动物基因组中放线蛋白基因的丢失。

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.