Meeting Abstract

P1.15  Monday, Jan. 4  BMP and Delta/Notch signaling control the development of amphioxus epidermal sensory neurons LU, T.M.; BRONNER-FRASER, M.; YU, J.K.S.*; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan ; Division of Biology, California Institute of Technology, Pasadena, California, USA ; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan jkyu@gate.sinica.edu.tw

Cephalochordates (lancelets, or amphioxus) are marine invertebrates that are grouped with vertebrate animals in the Chordate phylum because of shared features including the dorsal nerve chord, notochord, segmented somites, and pharyngeal gill slits. In addition to the central nervous system, amphioxus has a peripheral nervous system comprising several types of sensory neurons. One population of these sensory neurons, the type I receptors, originate near the ventral side of the embryo and then migrate dorsally in the neurula. These cells can be recognized by expression of some neuronal differentiation genes, including Hu/elav, and their morphology has been described by EM and dye labeling studies. However, the developmental mechanisms underlying the formation of these amphioxus sensory neurons are largely unknown, and their possible homology with the peripheral sensory neurons of other chordates remains elusive. We find that in amphioxus embryo, Delta/Notch signaling is involved in the specification of these sensory neurons from neighboring epidermal cells. Blocking Delta/Notch signaling pathway during late gastrula/early neurula stage results in a dramatic increase of sensory neurons along the flanks of the embryos. We further show that BMP signaling works upstream of Delta/Notch signaling to induce a ventral epidermal domain for generating these sensory neurons. Elevating BMP signaling level during blastula stage expands this domain dorsally. This intriguing similarity in patterning mechanism of these amphioxus epidermal sensory neurons with that of vertebrate neurogenic placodes, as well as ascidian ventral epidermal sensory neurons, supports their possible homology.