The Role of the Maternal Factors in Ascidian Development andEvolution

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This proposal describes experiments done with ascidian embryos, the simplest chordate embryos known. These embryos develop in a very similiar manner to other chordate embryos, including humans. The patterns of early cleavage, axis formation and gastrulation are well described in ascidians and a number of embryological experiments have shown that maternal factors in the egg are important in specifying tissues in the larvae. Dr. Swalla's lab has used two closely related ascidian species with very different larval phenotypes to isolate and characterize maternal factors necessary for normal larval development. They have isolated three novel genes that are present in the species that has a tailed tadpole larva and are absent in the species that has a tailless larva. Two of these genes are likely to be transcription factors that bind DNA and turn genes off and on, while the other is likely to be a signalling molecule involved in cell-cell communication. The experiments described in this proposal will investigate the role these proteins may play in development by characterizing the localization of the proteins in the eggs and embryos with antibodies and by examining possible protein-protein interactions. These results will give insight into how maternal proteins may be involved in developmental processes and cell specification during embryonic development. A long term goal of this laboratory is to then find similiar genes in vertebrate embryos and see what their role might be in these embryos.