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Evolution of the sponge body plan: Wnt and the development of polarity in freshwater sponges Open Access


Other title
Type of item
Degree grantor
University of Alberta
Author or creator
Windsor, Pamela J
Supervisor and department
Leys, Sally (Biological Sciences)
Examining committee member and department
Waskiewicz, Andrew (Biological Sciences)
Dacks, Joel (Cell Biology)
Pilgrim, David (Biological Sciences, Cell Biology)
Allison, Ted (Biological Sciences)
Abouheif, Ehab (Biology , McGill University, Montreal, QC)
Department of Biological Sciences
Molecular Biology and Genetics
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Body polarity is a fundamental aspect of all multicellular organisms. Metazoans – animals – are monophyletic, but is body polarity homologous among all phyla? Sponges are considered to have branched off first from other animals and therefore studies of polarity formation in the simple sponge body plan may hold key clues to fundamental metazoan characteristics like polarity. In this thesis, I studied the role of Wnt signaling in patterning the body axis of freshwater sponges. Lithium chloride caused the formation of extra oscula, the excurrent opening of the sponge canal system and transplant experiments showed the osculum can induce canal growth, similar to other animal tissue organizers. Phylogenetic analysis of sponge Wnt genes showed they are distinct from other animal Wnts and while I found no clear expression patterns by in situ hybridization, RNAi knockdown of gsk3 causes multiple oscula in the sponge. Attempts to express freshwater sponge wnts in Xenopus were unsuccessful. Sponges have indirect development through a non-feeding larva. Fates of larval cells in the adult sponge were followed using fluorescent probes. Ciliated cells surrounding the larva become choanocyte chambers in the juvenile, confirming the idea that inner and outer tissue layers are reversed with respect to other animals. Fluorescent labeling of the posterior pole of the larva revealed that this region becomes the osculum linking previously shown reports of wnt expression at the posterior pole with formation of the osculum and Wnt signaling. Taken together, the results here suggest that Wnt signaling in early metazoans played a role in the evolution of animal polarity.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Windsor, P.J., and Leys, S.P. 2010. Wnt signaling and induction in the sponge aquiferous system: evidence for an ancient origin of the organizer. Evol. Dev. 12: 484-493.Holstien, K., Rivera, A., Windsor, P., Ding, S., Leys, S.P., Hill, M., and Hill, A. 2010. Expansion, diversification, and expression of T-box Family genes in PoriferaRiesgo, A., Farrar, N., Windsor, P.J., Giribet, G., and Leys, S.P. 2014. The analysis of eight transcriptomes from all Porifera classes reveals surprising genetic complexity in sponges.

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