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Science 326 (5958): 1406-1410

Copyright © 2009 by the American Association for the Advancement of Science

Planarian Hh Signaling Regulates Regeneration Polarity and Links Hh Pathway Evolution to Cilia

Jochen C. Rink,* Kyle A. Gurley,* Sarah A. Elliott, Alejandro Sánchez Alvarado{dagger}

Abstract: The Hedgehog (Hh) signaling pathway plays multiple essential roles during metazoan development, homeostasis, and disease. Although core protein components are highly conserved, the variations in Hh signal transduction mechanisms exhibited by existing model systems (Drosophila, fish, and mammals) are difficult to understand. We characterized the Hh pathway in planarians. Hh signaling is essential for establishing the anterior/posterior axis during regeneration by modulating wnt expression. Moreover, RNA interference methods to reduce signal transduction proteins Cos2/Kif27/Kif7, Fused, or Iguana do not result in detectable Hh signaling defects; however, these proteins are essential for planarian ciliogenesis. Our study expands the understanding of Hh signaling in the animal kingdom and suggests an ancestral mechanistic link between Hh signaling and the function of cilia.

Department of Neurobiology and Anatomy, Howard Hughes Medical Institute, University of Utah School of Medicine, 401 MREB, 20 North 1900 East, Salt Lake City, UT 84103, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: sanchez{at}

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