Meeting Abstract
Metazoan ciliated sensory neurons and derivatives, such as the hair cells found in the vertebrate inner ear are hypothesized to share a common evolutionary origin. In the ascidian larva, the peripheral nervous system (PNS) consists of a series of ciliated epidermal sensory neurons (ESNs), which primarily run down the dorsal and ventral midlines of the tail. Our lab has shown that at least four transcription factors and at least one microRNA operate downstream of a Notch-Delta mediated mechanism which specifies PNS neurons from the midline epidermal cells. These molecules share conserved roles with the specification of vertebrate hair cells, supporting the hypothesis of a common evolutionary origin. Here we report on the identification of large numbers of genes that are shared between ESNs and hair cells as revealed by comparative RNA-SEQ of wild type and transgenic ascidian larvae. Our preliminary analysis identified multiple structural genes expressed in ascidian ESNs that are known components of the stereo cilia found in vertebrate hair cells including proteins found within the cilia, proteins that form tip link and ankle link connections and proteins which regulate ion homeostasis. In addition, we found that numerous mechanosensory channel proteins known to be expressed in hair cells are also expressed in the PNS ESNs. The ESNs are assumed to be mechanosensory, but this is the first direct molecular evidence that they express multiple proteins known to be required for such a function. Our results provide insight into the novel innovations that evolved within vertebrates to generate hair cells.
