Multiple Origins of Mesoderm in a Model Polychaete

许多动物在发育过程中从内胚层和外胚层产生第三层胚层，即中胚层。然而，中胚层发育潜力的细胞和分子分离以及这些不同起源的系统发育意义仍未被探索。显示一种称为螺旋分裂的高度刻板的细胞分裂程序的胚胎(例如，在包括软体动物、环节动物、新月形纲动物、吸虫、外包虫、多壳扁虫的动物中)是追踪幼虫/成虫结构来源的理想胚胎，并揭示了外胚层和内胚层的谱系。这项拟议的工作将分子和细胞方法与胚胎学操作结合在一起，在多毛类模型Capitella sp。我是一种节段性蠕虫，经历螺旋分裂，并在其整个生活史中增加新的节段。嵌合、尾端和夏娃在Capitella sp.中的表达我认为，胚胎后节段的中胚层不是由内胚层成纤维细胞产生的，而是由外胚层胚层前体产生的，这些前体在整个幼虫/幼虫生命过程中有效地进行原肠形成，并在末端添加过程中形成成体节段中胚层。在拟议的研究中，将研究外胚层和内胚层来源产生中胚层潜力的机制。Capitella sp.胚胎卵裂球的细胞内命运图谱。我将特别注意描述中胚层的胚胎学起源。已从Capitella sp.中鉴定出许多中胚层标记。I，并将被映射到细胞谱系上，以确定哪些基因与外胚层、内胚层或两者都有关联。在另一组实验中，将利用错误表达和敲除方法来确定选定的外胚层和内胚层基因的功能。这项拟议的研究将把科学培训与研究结合起来，并将包括夏威夷大学的本科生、研究生和博士后实习生。夏威夷大学是一家少数民族院校，也是EPSCoR州。国际学生联合会致力于在实验室环境中培训学生，包括来自太平洋岛民等代表性不足群体的学生。这项研究将为理解中胚层是如何在多毛类环节动物中产生的提供关键信息，并为第三胚层与蜕皮虫、后口动物和其他三倍体动物系统的发育提供重要的比较。

Many animals generate their third germ layer, the mesoderm, from both endomesodermal and ectomesodermal sources during development. However, the cellular and molecular segregation of mesodermal developmental potential and the phylogenetic significance of these distinct origins remain unexplored. Embryos that display a highly stereotyped cell cleavage program called spiral cleavage (e. g. in animals that include mollusks, annelids, nemerteans, sipunculids, echiurans, polyclad flatworms) are ideal for tracing sources of larval/adult structures and have revealed both ectomesodermal and endomesodermal lineages. The proposed work combines molecular and cellular approaches with embryological manipulations in a polychaete model, Capitella sp. I, a segmented worm that undergoes spiral cleavage and adds new segments throughout its life history. Expression of engrailed, caudal, and eve in Capitella sp. I suggests that mesoderm in post-embryonic segments is not generated from endomesodermal teloblasts, but rather from ectomesodermal precursors that effectively 'gastrulate' throughout larval/juvenile life and give rise to adult segmental mesoderm during the process of terminal addition. In the proposed study, the mechanism by which mesodermal potential is generated from ectodermal and endodermal sources will be examined. An intracellular fate map for embryonic blastomeres of Capitella sp. I will be generated with special attention towards characterizing embryological origins of mesoderm. A number of mesodermal markers have been identified from Capitella sp. I, and will be mapped onto the cell lineage to determine which genes are associated with ectomesoderm, endomesoderm, or both. In an additional set of experiments, mis-expression and knockdown approaches will be utilized to determine the function of select ecto- and endomesodermal genes. The proposed study will integrate scientific training with research, and will include undergraduate, graduate, and postdoctoral trainees at the University of Hawaii, a minority institution and EPSCoR state. The PI is committed to training students in the laboratory environment, including those from underrepresented groups such as Pacific Islanders. The study will provide crucial information towards understanding how mesoderm is generated in polychaete annelids, and provide an important comparison of development of the third germ layer with ecdysosoan, deuterostome and other triploblastic animal systems.