Patterning of the Ciona intestinalis Motor Ganglion

by

Alberto Sunao Stolfi

Doctor of Philosophy in Molecular and Cell Biology

University of California, Berkeley

Professor Michael S. Levine, Chair

Sea squirts are the closest living relatives to the vertebrates. The Motor Ganglion (MG) of the sea squirt Ciona intestinalis provides the basic excitatory drive of the central pattern generator (CPG) underlying swimming behavior of the tadpole. Despite its cellular simplicity, the MG shows molecular and physiological parallels to the spinal cord of vertebrates. Here I uncover the morphological diversity of MG neuronal subtypes, and show that this diversity is generated by sequential Ephrin/FGF/MAPK and Delta/Notch signaling events. Despite the divergent signaling requirements for patterning of this motor pool, I believe that the conserved downstream transcription factors might be operating to specify neuronal subtypes that are similar to those in the vertebrate spinal cord. Taking advantage of the experimental tractability of the Ciona embryo, I can generate a series of tadpoles with differing composition of moto- and interneuron subtypes, which could serve as the basis for elucidating the development and connectivity of a chordate locomotor CPG.