Smed-β-catenin-1 is required for anteroposterior blastema polarity in planarian regeneration

Planarian flatworms can regenerate heads at anterior- facing wounds and tails at posterior- facing wounds throughout the body. How this regeneration polarity is specified has been a classic problem for more than a century. We identified a planarian gene, Smed-beta catenin-1, that controls regeneration polarity. Posterior- facing blastemas regenerate a head instead of a tail in Smed-beta catenin- 1( RNAi) animals. Smed-beta catenin- 1 is required after wounding and at any posterior- facing wound for polarity. Additionally, intact Smed-beta catenin- 1( RNAi) animals display anteriorization during tissue turnover. Five Wnt genes and a secreted Frizzled- related Wnt antagonist- like gene are expressed in domains along the anteroposterior axis that reset to new positions during regeneration, which suggests that Wnts control polarity through Smed-beta catenin-1. Our data suggest that beta-catenin specifies the posterior character of the anteroposterior axis throughout the Bilateria and specifies regeneration polarity in planarians.