title: Expression of secreted Wnt pathway components reveals unexpected complexity of the planarian amputation response.
abstract: Regeneration is widespread throughout the animal kingdom, but our molecular understanding of this process in adult animals remains poorly understood. Wnt/β-catenin signaling plays crucial roles throughout animal life from early development to adulthood. In intact and regenerating planarians, the regulation of Wnt/β-catenin signaling functions to maintain and specify anterior/posterior (A/P) identity. Here, we explore the expression kinetics and RNAi phenotypes for secreted members of the Wnt signaling pathway in the planarian Schmidtea mediterranea. Smed-wnt and sFRP expression during regeneration is surprisingly dynamic and reveals fundamental aspects of planarian biology that have been previously unappreciated. We show that after amputation, a wounding response precedes rapid re-organization of the A/P axis. Furthermore, cells throughout the body plan can mount this response and reassess their new A/P location in the complete absence of stem cells. While initial stages of the amputation response are stem cell independent, tissue remodeling and the integration of a new A/P address with anatomy are stem cell dependent. We also show that WNT5 functions in a reciprocal manner with SLIT to pattern the planarian mediolateral axis, while WNT11-2 patterns the posterior midline. Moreover, we perform an extensive phylogenetic analysis on the Smed-wnt genes using a method that combines and integrates both sequence and structural alignments, enabling us to place all nine genes into Wnt subfamilies for the first time.
authors: Department of Neurobiology and Anatomy, Howard Hughes Medical Institute, University of Utah School of Medicine, 401 MREB, 20N 1900E, Salt Lake City, UT 84132, USA.
authors: Kyle A
authors: KA
authors: Gurley
authors: Sarah A
authors: SA
authors: Elliott
authors: Oleg
authors: O
authors: Simakov
authors: Heiko A
authors: HA
authors: Schmidt
authors: Thomas W
authors: TW
authors: Holstein
authors: Alejandro
authors: A
authors: Sánchez Alvarado
mesh_terms: D000671:Amputation, Surgical; D000818:Animals; D019521:Body Patterning / Q000235:genetics; D051157:Frizzled Receptors / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010802:Phylogeny; D010932:Planarians / Q000196:embryology / Q000235:genetics / Q000502:physiology*; D012038:Regeneration / Q000502:physiology*; D015398:Signal Transduction; D012995:Solubility; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism; D013623:Tail; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051157:Frizzled Receptors; D009419:Nerve Tissue Proteins; D051153:Wnt Proteins