Meeting Abstract

P1.39  Sunday, Jan. 4  Multipolar sponges: a putative role for Wnt signaling in the most basal metazoans WINDSOR, P.J.*; LEYS, S.P.; Univ. of Alberta; Univ. of Alberta pwindsor@ualberta.ca

The Wnt signaling pathways play important roles in multiple developmental mechanisms: oral-aboral patterning in cnidarians, tissue differentiation and cell migration in C. elegans, segment and limb polarity in Drosophila, and body polarity and patterning in vertebrates. Lithium chloride has classically been used in experimental embryology as a tool for understanding axial specification in animals ranging from cnidarians to vertebrates. Treatment with lithium mimics the Wnt signal, creating a constitutively active signal to transcribe downstream targets such as Hox genes. As a result, normal development of body polarity can be interrupted as seen in Hydra and Xenopus. We sought to understand the role of the Wnt pathway in a sponge using lithium treatment, as more familiar molecular tools such as RNAi are as yet unavailable for these animals. High doses of lithium caused sponges to lose essential traits in the normal functioning of a juvenile or adult individual, including the canal system that is responsible for current intake and thus feeding. Threshold doses of lithium produced sponges with a disorganized canal system with multiple excurrent openings (oscula) in 95% of individuals (n=21). Sponge polarity is determined mainly by the flow of water in and out of its canal system, so having multiple oscula indicates a multiplication of the main body axis. Wnt pathway components have only recently been identified within the sponge genome and no functional studies have been carried out to date. Future work will include further isolation and analysis of conserved Wnt pathway components including frizzled, beta-catenin and gsk-3beta, as well as attempting new methods for functional characterisation.