Expression of ptc1 and bmp2 in the regenerating caudal fin. Expression of ptc1 (A-E) was determined at 2 days (A,C) and 4 days (B,D,E) after amputation. (C-E) Proximodistal sections. (C) Two days after amputation, ptc1 is expressed in the basal epithelial layer of the wound epidermis just distal to the stump. (D,E) Four days after amputation, ptc1 is expressed at the same proximodistal level as shh but in 71% of the fins analyzed, it is not only expressed in the basal epithelial layer but also in the adjacent scleroblasts (D); in the remaining 29%, ptc1 is only expressed in a subset of cells of the basal epithelial layer (E). Expression of bmp2 (F-K) was determined at 4 days (F,I-K), 30 hours (G) and 2 days (H) after amputation. G-K are proximodistal sections. (H) Two days after amputation, bmp2 is expressed in cells of the basal epidermal layer just distal to the stump bone on each side of the fin and in adjacent scleroblasts. (I,J) At 4 days after amputation, bmp2 like ptc1 is expressed in 71% of the fins in the basal epithelial cells as well as in the scleroblasts (I); in the remaining 29%, bmp2 transcripts are only found in the epidermal compartment (J). (K) Another site of bmp2 at 4 days is a group of cells invading the space between the newly forming lepidotrichia and the epidermis as indicated by the single arrowhead. The double arrowhead in K indicates the distal domain of bmp2 expression. Arrows indicate the level of amputation. b, blastema; l, lepidotrichia; e, epidermis; s, scleroblasts. Scale bars, A,B, 80 μm; C,D,E,H,K, 30 μm; F, 65 μm; G,I,J, 25 μm.
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