Urochordate Origins of Neural Crest and Muscle

0212110杰弗里对脊索动物门中脊椎动物特征的起源知之甚少。 在这里，重点是方面的尿索动物的发展，预计将揭示新的光在进化和发展的这一重要问题。 总体目标是评估海鞘尾索动物两个关键脊椎动物特征的起源：（1）迁移神经嵴细胞和（2）由诱导过程指定的幼虫肌肉组织。 现代发育生物学中使用的海鞘物种（e。例如，在一个实施例中，玻璃海鞘、Molgula、海鞘和Halocynthia）表现出发育迅速、高度流线型的蝌蚪幼虫。 这些衍生的幼虫似乎缺乏迁移神经嵴细胞，只包含约40尾肌细胞，这主要是由本地化的细胞质决定因素。 流线型的蝌蚪，已经进化为快速扩散，并不代表大多数海鞘幼虫。 大多数海鞘物种有更大，发育缓慢的蝌蚪，更复杂的头部和强壮的尾巴，这可能代表了真正的祖先状态。 因此，杰弗里博士将在这里介绍海鞘Ecteinascidia turbinata作为一个实验系统，以研究在尿索动物的关键脊椎动物特征的起源。 外囊线虫是玻璃海鞘的近亲，它的蝌蚪幼虫巨大，头部有虹吸管雏形，感觉器官增大，咽鳃裂，尾部有1134个肌细胞。 海鞘与高度分化的蝌蚪的发展几乎被忽视，是成熟的分析使用现代技术。 Ecteinascidia系统将允许他联合收割机结合各种实验胚胎学和分子方法，包括使用正在进行的玻璃海鞘基因组和EST数据库，以研究发育的进化。 该建议专门针对Ecteinascidia胚胎中的神经嵴和肌肉发育。 首先，他将使用活体染料和基因标记研究相结合来确定外囊线虫胚胎是否具有与脊椎动物神经嵴细胞同源的迁移细胞。 他已经从DiI标记实验中获得了强有力的证据，证明存在迁移性神经嵴样细胞。 他将确定神经嵴样细胞的胚胎来源、区域迁移模式和发育命运，并将其特性与脊椎动物神经嵴细胞进行比较。 第二，他将确定是否在Ecteinascidia尾肌细胞的发展是由细胞质决定因素，在海鞘的流线型幼虫，或通过诱导过程，肌肉规格的脊椎动物的特点的方法的主要手段。 这些研究将通过细胞谱系追踪、原位mRNA和蛋白定位以及卵裂球分离和重组的组合来进行。 这些研究的智力价值在于，它们将为神经嵴细胞的进化历史和尾索动物尾肌发育的机制提供新的信息。 拟议活动的更广泛影响是，它将解决脊索动物门中关键脊椎动物特征的起源问题，并将我们未来的注意力集中在特定的脊索动物或非脊索动物群体上，以绘制复杂脊椎动物身体计划的进化起点。 最后，本研究计划透过将本科生纳入研究过程，以促进研究中的通识教育。

0212110JefferyLittle is known about the origins of vertebrate features in the Phylum Chordata. Here, the focus is on aspects of urochordate development that are expected to shed new light on this important problem in evolution and development. The overall goal is to assess the origins of two key vertebrate features in the ascidian urochordates: (1) migratory neural crest cells and (2) larval musculature specified by inductive processes. The ascidian species used in contemporary developmental biology (e. g., Ciona, Molgula, Styela, and Halocynthia) exhibit rapidly developing, highly streamlined tadpole larvae. These derived larva appear to lack migratory neural crest cells and contain only about 40 tail muscle cells, which are primarily specified by localized cytoplasmic determinants. The streamlined tadpoles, which have evolved for rapid dispersal, are not representative of most ascidian larvae. Most ascidian species have larger, slowly developing tadpoles with more complex heads and robust tails, which are likely to represent the true ancestral state. Accordingly, Dr. Jeffery will introduce here the ascidian Ecteinascidia turbinata as an experimental system to study the origin of key vertebrate features in the urochordates. Ecteinascidia, a close relative of Ciona, has a giant tadpole larva exhibiting a head with preformed siphon rudiments, enlarged sensory organs, and pharyngeal gill slits, and a robust tail with 1134 muscle cells. The development of ascidians with highly differentiated tadpoles has been virtually ignored and is ripe for analysis using modern technologies. The Ecteinascidia system will permit him to combine a variety of experimental embryological and molecular approaches, including use of ongoing Ciona genomic and EST databases, to study the evolution of development. This proposal specifically addresses neural crest and muscle development in Ecteinascidia embryos. First, he will determine whether Ecteinascidia embryos have migratory cells homologous to vertebrate neural crest cells using a combination of vital dye and gene marking studies. He already has strong evidence from DiI marking experiments that migratory neural crest-like cells are present. He will determine the embryonic sources, regional migration patterns, and developmental fates of the neural crest-like cells, and compare their properties to vertebrate neural crest cells. Second, he will determine whether the development of tail muscle cells in Ecteinascidia is controlled by cytoplasmic determinants, the predominant means of tail muscle specification in ascidians with streamlined larvae, or by inductive processes, the method of muscle specification characteristic of vertebrates. These studies will be carried out by a combination of cell lineage tracing, in situ mRNA and protein localization, and blastomere isolation and recombination. The intellectual merit of these studies is that they will provide new information on the evolutionary history of neural crest cells and the mechanisms of tail muscle development in the urochordates. The broader impacts of the proposed activity is that it will address the origin of key vertebrate features in the Phylum Chordata and focus our future attention on particular chordate or non-chordate groups in order to chart the evolutionary beginnings of the complex vertebrate body plan. Finally, the research is planned to foster general education in research by incorporating undergraduate students into the investigative process.