The Non-Vertebrate Chordate Oikopleura and Evolution of Vertebrate Developmental Innovations

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Vertebrate chordates have innovations not shared by non-vertebrate chordates, including neural crest, neurogenic placodes, skeletal features, and an amplified genome. The project's long-term objective is to learn how vertebrates evolved from non-vertebrate chordates. This work tests the hypothesis that vertebrates evolved the ability of neural plate border genes to turn on neural crest specifiers. The project tests predictions of the hypothesis in Oikopleura dioica, a larvacean with a fully sequenced genome, using novel methods to alter hundreds of embryos at once. Larvaceans are ubiquitous marine organisms that are considered basal chordates that contribute substantially to the biomass and carbon cycling of oceans. Oikopleura orthologs of neural crest-related genes will be cloned and in situ hybridization will be used to learn their expression patterns. Neural crest-related gene regulatory networks in Oikopleura will be dissected by performing gain- and loss-of-function experiments with Oikopleura orthologs of key crest-related genes, and results by in situ hybridization and genomic microarray will be evaluated. Public understanding will be enhanced of the roles of larvaceans in the environment and in the investigation of vertebrate origins. Achieving these aims will define developmental mechanisms that vertebrates evolved to develop a full blown neural crest and illuminate mechanisms by which evolutionary novelties arise. Because larvaceans, especially Oikopleura dioica, remove large quantities of the greenhouse gas carbon dioxide from the atmosphere for long-term storage in ocean depths, a better understanding of larvacean biology will help illuminate understanding of global warming. The project will educate school children about the role of larvaceans in ecology and the science of evolutionary biology and will mentor representatives of underrepresented groups, particularly minority undergraduates.