Wnt Signaling, Stem Cells and Regeneration in Cnidarians

Datum

14.03.2013

Zeit

16:00 - 17:00

Sprecher

Thomas W. Holstein

Zugehörigkeit

COS - Centre for Organismal Studies Heidelberg, Molecular Evolution and Genomics, Univ. Heidelberg

Sprache

en

Hauptthema

Biologie

Andere Themen

Biologie

Host

Jochen Rink

Beschreibung

Wnt Signaling, Stem Cells, and Regeneration in Cnidarians Molecular Evolution and Genomics, Centre for Organismal Studies Heidelberg, University of Heidelberg, Germany Cnidarians and other basal metazoans are well known for their remarkable regeneration capacity that is based on the activation of stem cells. We study regeneration in the freshwater polyp Hydra and found that regeneration starts with the restoration of a signaling center, i.e. the organizer. We are interested in the signaling cascades that constitute the regulatory network required for the robust patterning of this ancient signaling center. We identified Wnt genes in the fresh water polyp Hydra and in sea anemone Nematostella. Wnts are expressed at the side of the blastopore in many metazoan embryos and play an important role in axial patterning during metazoan development. Our data on the kinetics of Wnt gene expression during organizer formation in intact and regenerating animals reveals a cascade of consecutive Wnt activation with Wnt3 at the top of the cascade. Using transgenesis, we investigated cis-regulatory sequences of Hydra Wnt3 and found an autocatalytic regulatory network with repressive and activating inputs maintaining the organizer. This points to the importance of transcriptional regulation to localize the Wnt signaling center to a specific region along the body axis. New data on TGF-beta signaling indicate that this pathway is also important for the initiation of this organizing center during pattern formation. With respect to these new data, the molecular nature of the Hydra regeneration and the evolutionary conserved character of regeneration processes and stem cells will be discussed. References: Holstein TW (2012). The Evolution of the Wnt Pathway. Cold Spring Harb Perspect Biol 2012; cshperspect.a007922. Nakamura Y, et al. (2011). Autoregulatory and repressive inputs localize Hydra Wnt3 to the head organizer. PNAS 108: 9137-42 Chapman JA, et al. (2010). The dynamic genome of Hydra. Nature 464, 592-596

Letztmalig verändert: 15.03.2013, 09:02:34