Fig. 2

Wnt/β-catenin signaling is necessary for scale development.

(A) Wnt repression by heat-shock induction of hs:dkk1 transgene blocked scale formation, arrested fin outgrowth (yellow brackets) and prevented pelvic fin ray development (yellow arrow). (B) hs:dkk1 induction abrogated patterned expression of the Wnt/β-catenin reporter transgene 7x:TCF:mCherry (cyan). (C) hs:dkk1 larvae developed significantly fewer scales (n = 21) then heat-shocked controls (n = 13; p<0.0001). (D) Pectoral fins were significantly shorter in hs:dkk1 larvae (n = 21) than in heat-shocked controls (n = 13; p<0.0001). (E) hs:dkk1 larvae achieved a similar standard length (n = 21) to heat-shocked controls (n = 13; p=0.1). Plots indicate means ± SD. (F) Live image series of Wnt/β-catenin activity revealed by expression of 7xTCF:mCherry reporter transgene (cyan). Wnt/β-catenin reporter expression was first detected in a patch of epidermal cells in prospective scale regions (pre scale). Subsequently, sp7:EGFP+ dSFCs appeared underneath the 7xTCF:mCherry expressing cells (papilla). During later scale extension and imbrication, 7xTCF:mCherry expression persisted at the posterior margin in cells superficial and posterior to the scale forming cells. Scale bars, 1 mm (A); 100 µm (B,F).