Planaria flatworms can regenerate an entire organism from tiny body fragments, making them an ideal organism for the study of regeneration.β-catenin is important for the regeneration of posterior body parts in the planarian species Schmidtea mediterranea, which suggests that canonical Wnt signalling functions in this process, but this has yet to be confirmed experimentally. Now, on p. 905, Kerstin Bartscherer and co-workers demonstrate that the Wnt secretory protein Wntless/Evi and several planarian Wnt ligands regulate S. mediterranea regeneration. Through RNAi-mediated silencing of Smed-wntless and of all putative planarian Wnt genes, the authors show that, similar to Smed-β-catenin1, Smed-wntless,Smed-wnt11-2 and Smed-wntP-1 are required for posterior regeneration. Surprisingly, they also report that Smed-wntless and Smed-wnt5 are required for the proper regeneration of the planarian nervous system, and that this requirement is β-catenin independent. Thus,the authors suggest, planarian Wnts are important regulators of regeneration that signal through β-catenin-dependent and -independent pathways, all of which depend on Smed-Wntless/Evi.

2009