Practice question

Hydra head regeneration depends on establishment of head organizer at oral end. Wnt3 secreted from hypostome stabilizes beta-catenin by inhibiting destruction complex involving GSK3beta, Axin, APC, allowing nuclear translocation and TCF-mediated transcription of organizer genes. Transplantation of Wnt3-expressing tissue induces secondary axis. Pharmacological inhibition of Wnt with iCRT blocks head regeneration, while GSK3 inhibition hyperactivates producing ectopic heads. This conserved canonical Wnt-beta-catenin pathway parallels amphibian Spemann organizer, emphasizing ancient role of beta-catenin in axial organizer formation during morphallactic regeneration and maintaining continuous patterning in adult hydra polyp.