CAREER: Development of the Ascidian Peripheral Nervous System

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A key step in the evolution of vertebrates was the development of a large bony head containing specialized paired sensory organs that allowed vertebrates to become active predators. Vertebrate heads and the associated cells of the paired sensory organs are largely derived from two populations of cells, the neural crest and cranial placodes. Although research has led to a greater understanding of how neural crest and placodes are specified during vertebrate development, very little is known about their evolutionary origins. The proposed research will investigate the evolutionary and embryological origins of cranial placodes by examining the development of the ascidian larva peripheral nervous system (PNS). Ascidians are invertebrate chordates ideally suited for studying the evolution of chordate characteristics. The larval PNS, consisting of about three dozen cells that are primarily epidermal sensory neurons, shows similarities with placode-derived sensory cells both morphologically as well as in the expression patterns of key regulatory molecules. This research will determine the cell lineage and function of the PNS, and begin to define the gene-regulatory network specifying PNS development in the ascidian embryo. Graduate and undergraduate students will pioneer the use of three technologies to study marine invertebrate embryo development: (1) transgene-based cell-lineage analysis, (2) selective cell killing by the intracellular expression of a toxin and (3) in-vivo assays of gene function using RNA inhibition. Additionally, comparative-genomics approaches, in-situ hybridization, quantitative real-time PCR and analysis of transgenic embryos will be employed to decipher the PNS gene-regulatory network. These experiments will provide insights into the functional and gene-regulatory similarities between the ascidian larval PNS and vertebrate cranial placodes.This project will contribute to the development of the PI as a teacher-scholar. It incorporates educational programs for undergraduate, graduate, postgraduate and elementary school students and teachers. The proposed research will be performed primarily by graduate and undergraduate students. Student research will be published in scientific journals, and students will be encouraged to present their findings at scientific meetings. A series of year-long research opportunities for undergraduates, including a summer program, will provide 4 to 6 students with independent projects and a journal club focused on developmental biology and experimental techniques. New experimental approaches will be incorporated into an intense laboratory/lecture section on ascidian development for advanced graduate and postdoctoral fellows in the Woods Hole Embryology Course. Finally, an interactive Web site will be created for elementary-schoolstudents, providing them with a feel for biological research. The Web site will bring the laboratory into the classroom, exposing young students to the creativity and excitement involved in scientific research. This innovative program will serve as a model to encourage other laboratories to partner with elementary-school classrooms to provide improved science education to children.