Meeting Abstract
TGF-β superfamily signaling regulates a variety of developmental processes and has a conserved role in patterning the dorsal-ventral body axis. Within this signaling family, there are two distinct branches: the Activin/Nodal pathway and the BMP pathway. Recent studies in some spiralian species have suggested that BMPs play a crucial role in dorsal-ventral axis patterning. Here, we investigate patterning of the dorsal-ventral axis in annelids. Previous pharmacological inhibition studies in the annelid Capitella teleta suggests that signaling via the ALK4/5/7 receptor patterns the dorsal-ventral axis, implicating the Activin/Nodal pathway. In this study, we further determine the mechanism of the Activin/Nodal pathway as it functions in C. teleta axis patterning, as well as the role of TGF-β superfamily signaling in the more basally branching annelid, Chaetopterus variopedatus. In C. teleta embryos we utilize antisense Morpholino Oligos that target SMAD2/3, a pathway specific component, and then score larvae for phenotypic analyses. Secondly, early cleavage stage embryos of Chaetopterus were exposed to various chemical inhibitors, raised to larval stages, and scored for axial anomalies. Similarities between Chaetopterus and C. teleta are revealed as chemical interference with the Activin/Nodal pathway but not the BMP pathway results in larvae that lack detectable dorsal-ventral axes. Furthermore, our results suggest TGF-β superfamily signaling functions differently in annelids than in their spiralian counterparts, the mollusks. Comparative analysis using C. teleta and Chaetopterus sheds light on the mechanism of TGF-β signaling and the ancestral state of annelid dorsal ventral axis patterning, thus contributing to our understanding of how changes in developmental programs lead to evolution of spiralian body plans.
