Little is known about the evolutionary origin of the neural crest, a population of migratory embryonic cells with an amazing variety of derivatives in vertebrate embryos. Here, Dr. Jeffery proposes to continue a research program that identified potential homologues of neural crest cells in the ascidian Ecteinascidia turbinata, a tunicate chordate representing a group of marine animals that may be the sister group of vertebrates. He previously obtained evidence for the existence of neural crest-like cells (NCLC) in this ascidian species based on following cell migration from the dorsal embryonic midline, expression of neural crest markers, association with structures resembling placodes, which collaborate with neural crest cells to form many vertebrate features, and differentiation into body pigment cells, one of the prime vertebrate neural crest derivatives. These studies were facilitated by the usually large size of Ecteinascidia embryos and larvae, which permitted a merger of molecular with classical approaches for identifying candidates for neural crest-like cells (NCLC). Here he proposes to continue these studies in Ecteinascidia and in the model ascidian Ciona intestinalis, in which he has also recently discovered NCLC. The overall objective is to evaluate the hypothesis that ascidian NCLC and vertebrate neural crest cells had a common ancestry by exploring their embryonic origin(s), the expression patterns of key vertebrate neural crest regulatory genes, their migration pathways, and their developmental fates. In addition, he will explore the diversity of NCLC in ascidians by comparing these features in Ecteinascidia and Ciona, related species with highly divergent morphologies and life histories. This investigation will continue to combine classical embryological approaches, such as cell lineage, cell migration, and developmental fate analysis by vital dye marking, with molecular approaches, including gene expression analysis. In Ciona the objectives will be facilitated by the existence of the genome project and cDNA databases as well as the opportunity of transgenesis. These studies will provide insights into the evolutionary origin and history of neural crest cells, furnish novel information on the fates and diversity of ascidian NCLC, identify the similarities and differences between ascidian NCLC and vertebrate neural crest cells, and help to understand the evolution of vertebrates from an invertebrate chordate ancestor. A broad impact of this research is the continued integration of research and higher education, which is accomplished by involving undergraduate students in original research, by training pre-doctoral and post-doctoral investigators, and by our outreach to high school science programs. All of these activities include different genders and underrepresented minorities. The laboratory will continue to be a useful and highly appreciated local resource for teaching and illustrating evolutionary biology to high school students, and will also continue to serve as a resource for their short supervised science projects. The evolution of the neural crest is an excellent example of a morphological change that is experimentally tractable, has occurred within our own phylum, and is subject to interpretation as a novelty through conventional evolutionary theory. In addition to broad impacts directly related to the laboratory research, he will continue to participate in outreach activities related to primary and secondary school education and education of the lay public, including radio and TV broadcasts that explain the scientific evidence supporting evolution and highlight the seminal work of scientists working in this field, and to serve as advisor in the planning and writing of articles on evolution for the general public (Natural History Magazine) and for gifted children (Muse Magazine).
