Meeting Abstract

51.1  Sunday, Jan. 5 10:15  Specification the ascidian larval peripheral nervous system CHEN, J.S.; TANG, W.J.; MAHAFFY, J.M.; ZELLER, R.W.*; San Diego State Univ.; Benaroya Research Institute at Virginia Mason; San Diego State Univ.; San Diego State Univ. rzeller@mail.sdsu.edu

The peripheral nervous system of the ascidian Ciona intestinalis is composed of a number of ciliated epidermal sensory neurons (ESNs) that are present in the trunk and along the dorsal and ventral midlines of the larval tail. Other laboratories have shown that both FGF and BMP signaling in the early embryo are required for the proper specification of the ESNs in the larval tail. As in many biological systems, Notch-Delta mediated lateral inhibition is then used to specify the final number of ESNs in the larval tail. Here we define a preliminary gene regulatory network (GRN) that operates downstream of Notch-delta signaling. We performed a series of carefully staged in situ hybridizations and mis-expression studies to define this network. From these analyses we determined that at least four transcription factors function downstream of Notch-Delta: MyT1, Pou4, Atonal and NeuroD-like. Our studies established the epistatic interactions between these factors and determined that these transcription factors operate linearly. Interestingly, these same factors are known to be important for the specification of sensory neurons in a variety of bilaterians. Lastly, we show that the microRNA miR-124 is activated at the end of this transcription factor cascade and negatively feeds back on Notch-Delta signaling. Mathematical modeling of this feedback interaction has provided insight into how Notch-Delta activity patterns the ESNs along the embryonic tail midlines during development.