Meeting Abstract

P3.49  Wednesday, Jan. 6  Requirement for GSK-3 signaling in the early Ilyanassa oboleta embryo. SHUPE, KE*; HARRISON, CA; COOLEY, JR; NAGY, LM; University of Arizona lnagy@email.arizona.edu

Canonical Wnt signaling plays a key role in determining axial polarity and cell fate identity across a diverse array of organisms. Here we report our findings concerning the role of Wnt signaling in the marine mud snail Ilyanassa obsoleta, with particular attention to its function during the early cleavage divisions and the establishment of axial polarity. We characterized the embryonic expression profiles of Ilyanassa Wnt4, Wnt5b and Wnt7 orthologs. IoWnt7 is maternally provided and shows an 8 fold increase in abundance at the 16 cell stage, while IoWnt4 and Wnt5b are not expressed until 45 hours of development and show a 1000 fold increase after 65hrs, when we observe an overall burst in zygotic transcription. We also characterized the effects of treating early Ilyanassa embryos with alsterpaullone, a selective inhibitor of GSK-3, which mediates the proteasomal destruction of β-catenin. Embryos exposed to alsterpaullone for 24 hours lacked eyes, shell, and velum and were characterized by large, irregularly shaped patches of cilia and pigmentation. Nanos expression, which marks the early division progeny of 4d (the endomesodermal precursor cell) was normal in drug-treated embryos. Engrailed expression, which marks the developing shell field, was absent or reduced to a few irregularly positioned cells. Progressively later application of the drug resulted in a progressive recovery of cell fates. The results are consistent with a role for GSK-3 signaling during the first 5 cleavage cycles in Ilyanassa development.