Meeting Abstract
Bilaterians with clear anterior-posterior (AP) and dorsal-ventral (DV) axes represent a major transition in early animal evolution. Most bilaterian lineages show a restriction of the central nervous system (CNS) along the DV axis, ventrally in protostomes and dorsally in chordates. The DV axis and the accompanying CNS regionalization are generally controlled by Bmp (Bone morphogenetic protein) signaling across many bilaterians. Acoels, members of the outgroup lineage to all other bilaterians, have a DV axis under Bmp control, but their nervous system is not restricted to one side. Previous studies have supported the idea that the role for Bmp/Chordin in axial patterning may have preceded a role in neural patterning. Therefore, studies of the nervous system patterning in acoels can reveal the evolution of the mechanisms through which Bmp signaling controls the nervous system. We utilized Hofstenia miamia, an acoel species that is amenable to functional investigation of nervous system patterning during both development and regeneration. As a first step, we sought to determine the nervous system architecture of H. miamia by identifying and characterizing its neural genes. We identified homologs of all major neurotransmitter synthesis pathway genes as well as neurotransmitter receptors in the H. miamia transcriptome. Based on fluorescent in situ hybridization, we found three major subepidermal regions along the anterior-posterior axis that contain a diversity of neural cell types – an oral “ring”, an anterior domain with ventral lobe-like structures, and the remainder of the body with sparsely-distributed cells. The identification of these major neural subpopulations will enable a functional investigation of mechanisms that control the localization of neural cells along the DV axis.
