Collaborative Research: Developmental, Molecular and Evolutionary Analysis of Chaetognaths: A Deuterostome-Like Ecdysozoan

毛网虫，或称“箭虫”，是世界上所有海洋中发现的最丰富的海洋无脊椎动物之一。这一无处不在的动物群体的系统发育地位目前尚不清楚。直到最近，根据其径向卵裂程序、典型的肠腔、胚孔的后部位置和三部分成体计划等发育特征，毛节被认为是基础后口动物。新的分子证据，包括本提案中提供的HOX基因数据表明，毛节动物不是后口动物，而是与节肢动物和线虫等蜕皮动物关系密切的基生原口动物。事实上，在洞察原生动物体型进化方面，毛节动物现在被认为是最关键和最未被研究的后生动物群体之一。然而，关于毛发发育的细胞和分子研究很少。Martindale博士和Halanych博士的建议描述了一套全面的、多学科的方法，旨在描述Chaetognath胚胎是如何工作的。利用现代发育(细胞内细胞谱系标记和激光细胞删除实验)和分子(克隆、原位杂交)技术，Martindale和Halanych将收集这些有趣动物正常发育的重要信息，并能够研究后生动物遗传调控机制的保护。此外，基因发现技术(EST筛选)将为人体计划进化的祖先机制提供有价值的新信息。这些数据不仅对确定毛节动物的系统发育位置很重要，而且还为蜕皮动物分支的进化和发育程序的“进化性”提供了分子和发育方面的见解。Chaetognath可能是现有的最具信息量和最易处理的基础无脊椎动物系统，它将使人们能够了解线虫和节肢动物支系的进化，这两个物种是地球上遗传研究最多的两个动物群体。

0236479HalanychThe chaetognaths, or "arrow worms", are one of the most abundant marine invertebrates found in all the world's seas. The phylogenetic position of this ubiquitous group of animals is currently unknown. Until recently, chaetognaths were considered to be basal deuterostomes based on developmental features such as their radial cleavage program, classic enterocoeley, posterior position of the blastopore, and tripartite adult body plan. New molecular evidence, including Hox gene data presented in this proposal, has suggested that chaetognaths are not deuterostomes but basal protostomes closely allied with ecdysozoans such as arthropods and nematodes. In fact, chaetognaths are now thought to be one of the most pivotal and understudied groups of metazoan animals for gaining insight into the evolution of protostome body plans. Only a handful of cellular and molecular investigations of chaetognath development have ever been made, however. Drs. Martindale and Halanych's proposal describes a comprehensive and multidisciplinary set of approaches designed to characterize how chaetognath embryos "work". Using both modern developmental (intracellular cell lineage labeling and laser cell deletion experiments) and molecular (cloning, in situ hybridization) techniques, Martindale and Halanych will collect vital information on the normal development of these interesting animals, and be able to and examine the conservation of genetic regulatory mechanisms in the Metazoa. In addition, techniques of gene discovery (EST screening) will provide valuable new information on the ancestral mechanisms of body plan evolution. These data will not only be important to determine the phylogenetic position of chaetognaths, but to also provide molecular and developmental insight in to the evolution of the ecdysozoan clade, and the "evolveability" of developmental programs. Chaetognaths could be the most informative and tractable basal invertebrate system available that will allow an understanding of the evolution of the nematode and arthropod clades, the two most genetically heavily studied group of animals on earth.