Evolution of Axial Patterning

越来越多的证据表明，一套共同的调控基因参与了一套共同的或相关的机制，构成了迄今为止所研究的后生动物许多发育过程的基础。 这些基因在后生动物进化过程中出现的时间有多早？它们的功能在多大程度上被保存下来？ 解决这些问题的一个有用的方法是研究刺胞动物中的这些基因，刺胞动物是第一组具有明确身体计划的动物。 在刺胞动物中，水螅是特别有用的，因为它的发育过程被广泛了解。 拟议工作的总体目标是确定水螅中轴形成和轴模式的基因和机制是否与脊椎动物和节肢动物相似。 四个详细的目标如下：在水螅中，轴的形成和轴的图案可以在芽的形成过程中进行研究，动物的无性生殖形式。 其中两个目标侧重于阐明芽形成的各个方面。 [1]在水螅的三种细胞谱系中，两种上皮谱系[外胚层和内胚层]起着明显的作用。 间质细胞谱系的可能作用将通过改变或消除该谱系的操作来研究。 [2]在脊椎动物和果蝇中发现的轴向模式基因的一些同源物已经从水螅中分离出来，并显示在芽形成过程中表达。 将针对这些基因的反义寡核苷酸引入出芽组织，将对它们的特殊作用进行更直接的研究。另外两个目标集中在分离水螅中参与轴向模式的新基因。 一种方法是寻找参与背腹图案形成的基因的同源物，这在脊椎动物和果蝇中是高度保守的。 另一个涉及到在青蛙胚胎中诱导第二轴，以确定涉及轴向图案的水螅基因。 任何基因分离的程序将检查其轴模式在水螅的作用，通过检查他们的表达模式在各种发展的情况下，以及使用反义的方法，以获得更直接的信息。结果应该扩展轴的形成以及如何与一个单一的轴动物进化到一个以上的轴动物的进化的理解。

Accumulating evidence indicates is that a common set of regulatory genes involved in a common, or related, set of mechanisms underlie many of the developmental processes of the metazoans studied so far. How early did these genes arise during metazoan evolution and to what extent has their function been conserved? A useful approach to these questions is to study such genes in a cnidarian, the first group of animals to have a defined body plan. Among the cnidaria, hydra is particularly useful as the developmental processes are extensively understood. The overall aim of the proposed work is to determine if the genes and mechanisms underlying axis formation and axial patterning in hydra are similar to those found vertebrates and arthropods. The four detailed aims are the following.In hydra, axis formation and axial patterning can be studied during the process of bud formation, the animal's asexual form of reproduction. Two of the aims focus on clarifying aspects of bud formation. [1] Of the three cell lineages in hydra, the two epithelial lineages [ectoderm and endoderm] play an obvious role. A possible role of the interstitial cell lineage will be investigated by manipulations that alter or eliminate this lineage. [2] A number of homologues of axial patterning genes found in vertebrates and Drosphila have been isolated from hydra and show to be expressed during bud formation. More direct evidence of their particular roles will be investigated by introducing anti-sense oligonucleotides against such genes into budding tissue.The other two aims focus on the isolation of new genes involved in axial patterning in hydra. One approach will be to look for homologues of genes involved in dorsal-ventral patterning, which is in part, highly conserved among vertebrates and Drosophila. The other involves using the induction of a 2nd axis in frog embryos to identify hydra genes involved in axial patterning. Any genes isolated with either procedure will be examined for their role in axial patterning in hydra by examining their expression patterns in a variety of developmental situations as well as using the anti-sense approach to gain more direct information.The results should extend the understanding of the evolution of axis formation as well as how animals with a single axis evolved into animals with more than one axis.