The Evolution of Embryonic Polarity: A Molecular and Phylogenetic Approach

这笔赠款的重点是了解胚胎轴性的发育和进化起源，这些特性负责组织小的孤立海葵Nematostella vetensis(珊瑚目，线虫纲)生殖层的分离。珊瑚虫是双倍母细胞的基本成员，呈“放射状”对称，是所有两侧对称的三倍母细胞后生动物的姊妹门。与两侧对称的后生动物不同，媒介微体虫卵没有明显的分子极性，在受精时或受精后不久产生的不对称性导致核β-连环蛋白信号在未来的原肠形成部位被激活。由于像媒介线虫这样的线虫拥有许多参与双边动物中轴组织的相同基因，他们有可能深入了解导致所有多细胞动物中卵子各向异性进化的机制。将追求三个特定的目标：1)使用实验胚胎学方法表征媒介线虫卵子/受精卵中轴形成的开始和发育极性的起源，2)鉴定PAR蛋白在建立媒介线虫受精卵早期不对称性中的作用，并确定这些蛋白在调节不对称β-连环蛋白信号中的可能作用。这些实验将在蛇类动物中确定PAR基因的功能，并将揭示蛇类动物是否像双侧动物那样使用这些基因来极化早期的卵子/胚胎。此外，这些实验将揭示PAR蛋白是否在极化典型的Wnt信号中发挥作用，3)产生关键试剂，并进一步开发必要的方法学，进一步利用媒介新菌作为发育和进化研究的模式系统。这项工作是第一次对珊瑚虫线虫发育进行全面的实验和分子分析。它提供了一个独特的机会来了解这些胚胎是如何“工作”的，从而为更普遍研究的双边系统的发展提供了洞察力。这些研究将把精子来源的不对称性与PAR蛋白的定位和Wnt/β-catenin信号转导通路的激活联系起来，从而为深入了解A/V轴的进化和生殖层的进化提供依据。拟议的工作涉及博士后、研究生和本科生，他们来自科学界代表性不足的群体。这项研究的发现也将被纳入本科生和研究生的课程。此外，拟议的协作工作还将改善夏威夷大学的研究和培训基础设施。

AbstractThis grant is focused on understanding the developmental and evolutionary origin of embryonic axial properties that are responsible for organizing the segregation of germ layers in a small solitary sea anemone Nematostella vectensis (Anthozoa, Cnidaria). Anthozoans are basal members of the diploblastic, "radially" symmetric Cnidaria: the sister phylum to all bilaterally symmetrical triploblastic metazoans. Unlike bilaterally symmetrical metazoans, N. vectensis eggs have no apparent molecular polarity, and asymmetries generated at, or soon after, fertilization result in the activation of nuclear beta-catenin signaling at the future site of gastrulation. Because cnidarians like N. vectensis possess many of the same genes involved in axial organization in bilaterians, they have the potential to provide insight into the mechanisms that led to the evolution of egg anisotropies in all multicellular animals.Three specific aims will be pursued: 1) To use experimental embryological methods to characterize the onset of axis formation and origins of developmental polarity in the N. vectensis egg/zygote, 2) To identify the roles of the PAR proteins in establishing early asymmetries in the N. vectensis zygote and determine the possible role of these proteins in regulating asymmetric beta-catenin signaling. These experiments will establish the function of the par genes in a cnidarian and will reveal if cnidarians use these genes to polarize the early egg/embryo as in bilaterians. Additionally, these experiments will reveal if the PAR proteins play a functional role in polarizing canonical Wnt signaling, 3) To produce the critical regents and further develop methodologies necessary for further exploitation of N. vectensis as a model system for developmental and evolutionary studies.This work is the first comprehensive experimental and molecular analysis of anthozoan cnidarian development. It provides a unique opportunity to understand how these embryos "work", and thus provide insight into the development of more commonly studied bilaterian systems. These studies will link sperm-derived asymmetries to the localization of the PAR proteins and the activation of the Wnt/beta-catenin signal transduction pathway, and thus, provide insight into the evolution of the A/V axis and the evolution of germ layers. The proposed work involves postdocs, graduate students and undergraduate students from groups under-represented in science. The findings from this research will also incorporated into the undergraduate and graduate curricula. Additionally, the proposed collaborative work will also improve the research and training infrastructure at the University of Hawaii.