Molecular Basis of Hydra Patterning

多细胞动物进化过程中的一个关键创新是形成和维持身体轴的能力。刺胞动物是最早分化的具有明确轴向模式的动物。这种模式可能与原口动物和后口动物胚胎的前/后轴模式相关的分子进化机制有关。如果是这样的话，研究者就会得出结论，在现存的后生动物的进化过程中，轴向模式只进化了一次。另外，水螅的轴向模式的分子机制可能在很大程度上甚至完全不同于最近分化的动物。这一发现表明，在后生动物的进化过程中，轴向模式进化了不止一次。这些可能的结果中的任何一个都将对理解多细胞动物的进化产生重大影响。许多基因已经被确定，这些基因是参与淡水刺胞水螅轴向图案的有吸引力的候选者。然而，由于缺乏在成年水螅中导入和表达克隆基因的方法，因此不可能对这些基因在轴向模式中的作用进行功能测试。本项目的目标是开发一种在九头蛇中获得外源基因产物表达的方法。将采取若干途径。这些方法包括：(1)使用泛嗜性逆转录病毒作为载体，将克隆基因稳定地导入水螅胚胎或成年息肉的精原细胞；(2)向胚胎中微量注射DNA；(3)通过粒子轰击将DNA导入胚胎和成年息肉；(4)利用tat介导的蛋白质摄取系统将蛋白质引入成年息肉细胞。

A key innovation during the evolution of multicellular animals was the ability to form and maintain a body axis. Cnidarians are the earliest diverging animals in which a clearly defined axial pattern exists. This pattern could be established by molecular mechanisms evolutionarily related to those responsible for patterning of the anterior/posterior axis in the embryos of protostomes and deuterostomes. If this was the case, the investigator would conclude that axial patterning evolved only once during the evolution of extant metazoans. Alternatively, the molecular mechanisms of axial patterning in the Hydra polyp could be largely or even completely distinct from those used in more recently diverged animals. Such a finding would indicate that axial patterning evolved more than once during the evolution of metazoans. Either of these possible outcomes will have a major impact on understanding the evolution of multicellular animals.A number of genes have been identified which are attractive candidates for involvement in axial patterning in the freshwater cnidarian Hydra. Functional tests of these roles of theses genes in axial patterning have, however, not been possible due to the lack of methods for introduction and expression of cloned genes in adult Hydra polyps. The goal of this project is the development of a method for obtaining expression of exogenous gene products in Hydra. Several avenues will be pursued. These include: (1) use of a pantropic retrovirus as a vector for stable introduction of cloned genes into Hydra embryos or into the spermatogonial cells of the adult polyp; (2) microinjection of DNA into embryos; (3) introduction of DNA into embryos and adult polyps via particle bombardment; and (4) introduction of proteins into the cells of adult polyps using the TAT-mediated protein uptake system.