GRAINGER, R.M.; University of Virginia, Charlottesville: Xenopus tropicalis, a new model for vertebrate developmental genetics

The pipid frog Xenopus laevis has been among the most productive model systems for vertebrate experimental embryology. Development of genetic approaches in this system would provide a very powerful complement to embryological methods when trying to understand complex developmental processes. Several advances in the Xenopus system provide further impetus for developing an amphibian genetic model. First, recently developed transgenic technology permits transgenic frogs to be produced cheaply, efficiently, and in large numbers. In addition, recent efforts to develop genomic tools in Xenopus, including an extensive EST database, provide further resources that would be greatly enhanced in conjunction with genetic approaches. Because of its duplicated genome and long generation time, Xenopus laevis is not ideal for genetic studies, but a close relative, Xenopus (Silurana) tropicalis, which has a much shorter generation time (3-4 months) and a smaller diploid genome, is an excellent prospect. The embryological techniques and molecular assays which have been described for X. laevis are readily applied to X. tropicalis, but may be supported by multigeneration genetic analyses. Using mutants or transgenic animals in highly-developed tissue transplantation regimes will facilitate analysis of individual animals containing tissues of more than one genotype. Such genetic mosaic analyses have been very useful in studies of Drosophila embryogenesis, but are technically challenging in extant vertebrate models. Recent progress with the Xenopus tropicalis system, including discussion of several developmental mutations, will be presented.