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Fig. S2 Expression of markers for the blastema and the basal epidermal layer are impaired in the absence of RA signaling. Whole-mount in situ hybridization demonstrates that neither the blastema nor the basal epidermal layer is formed or specified correctly in heat-shocked hsp70:cyp26a1 fish (daily heat shocks, first heat shock 2 hours before amputation). (A-C) In wild-type regenerates, msxb and fgf20a are strongly expressed in cells of the forming blastema at 32 or 46 hpa. Expression of both genes is undetectable in regenerates of hsp70:cyp26a1 fish. (D,E) Expression of lef1, which marks the basal epidermal layer and distal blastema cells in wild-type regenerates, is absent in hsp70:cyp26a1 fins at 32 and 48 hpa. Dashed lines indicate the amputation plane. hs, heat shock. Scale bar: 200 μm.