Molecular Basis of Hydra Patterning

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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.