Evolutionary Origin of the Neural Crest

关于神经嵴的进化起源知之甚少，神经嵴是一群具有惊人多样性的脊椎动物胚胎衍生物的迁移胚胎细胞。在这里，Jeffery博士建议继续一项研究项目，以确定腹水鞘（Ecteinascidia turbinata）神经嵴细胞的潜在同源物。腹水鞘是一种被囊脊索动物，代表了一群可能是脊椎动物姐妹群的海洋动物。他先前根据细胞从背胚中线的迁移、神经嵴标记物的表达、与类似基板的结构的关联（与神经嵴细胞合作形成许多脊椎动物特征）以及向体色素细胞（脊椎动物神经嵴的主要衍生物之一）的分化，在该海鞘物种中获得了神经嵴样细胞（NCLC）存在的证据。这些研究得益于外海鞘胚胎和幼虫的大尺寸，这使得分子与经典方法相结合，可以识别神经嵴样细胞（NCLC）的候选细胞。在这里，他建议在外海鞘和模型海鞘中继续这些研究，他最近也在其中发现了NCLC。本研究的总体目标是通过探索海鞘NCLC和脊椎动物神经嵴细胞的胚胎起源、关键神经嵴调控基因的表达模式、迁移途径和发育命运，来评估它们具有共同祖先的假设。此外，他将通过比较海鞘和海鞘这两个形态和生活史高度不同的亲缘物种的这些特征，探索海鞘中NCLC的多样性。这项研究将继续结合经典的胚胎学方法，如细胞谱系、细胞迁移和通过重要染料标记进行的发育命运分析，以及分子方法，包括基因表达分析。在中国，基因组计划和cDNA数据库的存在以及转基因的机会将促进这些目标的实现。这些研究将为神经嵴细胞的进化起源和历史提供新的见解，提供有关海鞘NCLC的命运和多样性的新信息，确定海鞘NCLC与脊椎动物神经嵴细胞的异同，并有助于理解脊椎动物从无脊椎脊索动物祖先的进化。这项研究的一个广泛影响是研究和高等教育的持续整合，这是通过让本科生参与原创性研究，通过培训博士前和博士后研究人员，以及通过我们向高中科学项目的推广来实现的。所有这些活动都包括不同性别和未被充分代表的少数民族。该实验室将继续是一个有用的和高度赞赏的本地资源，为高中学生教学和说明进化生物学，也将继续作为他们短期监督科学项目的资源。神经嵴的进化是形态学变化的一个很好的例子，这种变化在实验上是可处理的，发生在我们自己的门中，并且通过传统的进化理论可以解释为一种新奇的东西。除了与实验室研究直接相关的广泛影响外，他还将继续参与与中小学教育和普通公众教育有关的推广活动，包括广播和电视广播，解释支持进化论的科学证据，并强调在这一领域工作的科学家的开创性工作。为公众（《自然历史杂志》）和天才儿童（《缪斯杂志》）策划和撰写关于进化论的文章，担任顾问。

Little is known about the evolutionary origin of the neural crest, a population of migratory embryonic cells with an amazing variety of derivatives in vertebrate embryos. Here, Dr. Jeffery proposes to continue a research program that identified potential homologues of neural crest cells in the ascidian Ecteinascidia turbinata, a tunicate chordate representing a group of marine animals that may be the sister group of vertebrates. He previously obtained evidence for the existence of neural crest-like cells (NCLC) in this ascidian species based on following cell migration from the dorsal embryonic midline, expression of neural crest markers, association with structures resembling placodes, which collaborate with neural crest cells to form many vertebrate features, and differentiation into body pigment cells, one of the prime vertebrate neural crest derivatives. These studies were facilitated by the usually large size of Ecteinascidia embryos and larvae, which permitted a merger of molecular with classical approaches for identifying candidates for neural crest-like cells (NCLC). Here he proposes to continue these studies in Ecteinascidia and in the model ascidian Ciona intestinalis, in which he has also recently discovered NCLC. The overall objective is to evaluate the hypothesis that ascidian NCLC and vertebrate neural crest cells had a common ancestry by exploring their embryonic origin(s), the expression patterns of key vertebrate neural crest regulatory genes, their migration pathways, and their developmental fates. In addition, he will explore the diversity of NCLC in ascidians by comparing these features in Ecteinascidia and Ciona, related species with highly divergent morphologies and life histories. This investigation will continue to combine classical embryological approaches, such as cell lineage, cell migration, and developmental fate analysis by vital dye marking, with molecular approaches, including gene expression analysis. In Ciona the objectives will be facilitated by the existence of the genome project and cDNA databases as well as the opportunity of transgenesis. These studies will provide insights into the evolutionary origin and history of neural crest cells, furnish novel information on the fates and diversity of ascidian NCLC, identify the similarities and differences between ascidian NCLC and vertebrate neural crest cells, and help to understand the evolution of vertebrates from an invertebrate chordate ancestor. A broad impact of this research is the continued integration of research and higher education, which is accomplished by involving undergraduate students in original research, by training pre-doctoral and post-doctoral investigators, and by our outreach to high school science programs. All of these activities include different genders and underrepresented minorities. The laboratory will continue to be a useful and highly appreciated local resource for teaching and illustrating evolutionary biology to high school students, and will also continue to serve as a resource for their short supervised science projects. The evolution of the neural crest is an excellent example of a morphological change that is experimentally tractable, has occurred within our own phylum, and is subject to interpretation as a novelty through conventional evolutionary theory. In addition to broad impacts directly related to the laboratory research, he will continue to participate in outreach activities related to primary and secondary school education and education of the lay public, including radio and TV broadcasts that explain the scientific evidence supporting evolution and highlight the seminal work of scientists working in this field, and to serve as advisor in the planning and writing of articles on evolution for the general public (Natural History Magazine) and for gifted children (Muse Magazine).