Fig. 3. Amputation level controls the amount of Fgf target gene expression during regeneration. In situ hybridization analysis of Fgf target gene expression in 3 dpa double-amputated fins (33°C). (A) A representative section from a single-amputated fin demonstrates expression for mkp3, sef and spry4 in both the basal epidermal layer and the distal region of the blastema (arrowheads indicate in situ hybridization signals). (B) Whole-mount images for each gene show proximal and distal regenerates of the same double-amputated fin. mkp3 (15 out of 24 regenerates), sef (8 out of 11 regenerates) and spry4 (12 out of 18 regenerates) were usually expressed more strongly in proximal regenerates than distal. We never detected greater expression of these genes in distal regenerates.