Evolutionary Origin of the Neural Crest

关于神经脊的进化起源，人们知之甚少。神经脊是脊椎动物胚胎中一群具有令人惊叹的各种衍生品的迁徙胚胎细胞。在这里，杰弗里博士提议继续一项研究项目，以确定海鞘动物海鞘中神经脊细胞的潜在同源物。海鞘动物是一种被囊脊索动物，代表一群海洋动物，可能是脊椎动物的姐妹群。他之前获得的证据表明，这种海鞘物种中存在神经峰样细胞(NCLC)，其依据是细胞从胚胎中线背侧的迁移，神经峰标志物的表达，与类似于安慰剂的结构的联系(与神经峰细胞合作形成许多脊椎动物的特征)，以及分化为体色素细胞，体色素细胞是脊椎动物最主要的神经峰衍生物之一。这些研究是由通常较大的外囊尾虫胚胎和幼虫推动的，这使得分子和经典方法相结合，以确定神经峰样细胞(NCLC)的候选细胞。在这里，他建议继续在外囊和模型海鞘动物中进行这些研究，他最近也在其中发现了NCLC。总体目标是通过探索海鞘细胞和脊椎动物神经脊细胞的胚胎起源(S)、关键的脊椎动物神经脊调节基因的表达模式、它们的迁移途径以及它们的发育命运来评估海鞘神经脊细胞和脊椎动物神经脊细胞具有共同祖先的假设。此外，他还将通过比较海鞘和海鞘这两个形态和生活史高度不同的近缘物种的这些特征，来探索海鞘中NCLC的多样性。这项研究将继续将经典的胚胎学方法，如细胞谱系、细胞迁移和生命染料标记的发育命运分析，与包括基因表达分析在内的分子方法相结合。在Ciona，基因组项目和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。这些研究将为了解神经脊细胞的进化起源和历史提供新的信息，为海鞘类NCLC的命运和多样性提供新的信息，识别海鞘类NCLC和脊椎动物神经脊细胞的异同，并有助于理解脊椎动物从无脊椎动物脊索祖先进化而来。这项研究的广泛影响是研究与高等教育的持续整合，这是通过让本科生参与原创研究，通过培训博士后和博士后研究人员，以及通过我们对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代表性不足的少数群体。该实验室将继续是一个有用的和高度赞赏的当地资源，用于向高中生教授和说明进化生物学，也将继续作为他们的短期监督科学项目的资源。神经脊的进化是形态变化的一个很好的例子，这种变化在实验上是容易处理的，发生在我们自己的门中，并受到传统进化理论作为一种新奇事物的解释。除了与实验室研究直接相关的广泛影响外，他还将继续参加与中小学教育和普通公众教育有关的外联活动，包括电台和电视广播，解释支持进化论的科学证据，突出这一领域科学家的开创性工作，并在为普通公众(《自然历史杂志》)和天才儿童(《缪斯》杂志)规划和撰写有关进化论的文章方面担任顾问。

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).