Wnt/β-catenin signaling is required for zebrafish tail fin regeneration. (A) Experimental scheme. Tail fins were amputated from wild-type, hsDkk1GFP or hsΔTcfGFP transgenic zebrafish and heat shocks were applied twice daily for the time periods indicated by the colored lines. (B) Continuous suppression of Wnt target gene expression in hsΔTcfGFP (n=15), or reduction of Wnt/β-catenin signaling in hsDkk1GFP transgenic fish (n=19), for 7 days starting shortly before amputation inhibits fin regeneration. Live fins were photographed at 1 dpa (left panels) and 7 dpa (right panels). (C) Overexpression of Dkk1 starting at 1 dpa inhibits fin regeneration (left panel; n=18); overexpression from 3 dpa results in partial inhibition of regeneration (right panel; 11 of 15 fins). Live fins were photographed at 7 dpa; corresponding wild-type controls regenerated normally (not shown).