Fig. 6

Evidence that Dkk1b-Producing ETs Inhibit Blastema Formation after Fin Amputation

(A) Whole-mount image of male pectoral fin (left). Quantification of intrafin ratio of regenerate lengths at 4 dpa (right). The ratio of anterior (Ant) ray length to posterior (Pos) ray length was calculated separately for each animal as indicated. Regeneration of male anterior regions was inhibited when fins were amputated through regions containing proximal ETs (P and Prox; 50% amputation) but not through distal regions (D and Dis; 10%–20% amputation). Arrowheads indicate amputation planes. n = 18, mean ± SD. p < 0.001 by one-way analysis of variance (ANOVA) with Bonferroni posttest.

(B) Quantification of intrafin ratio in adult females after 14 days of treatment with Eth, followed by 1 day of washout. Conditions that stimulated formation of dense dkk1b:EGFP⁺ ETs were sufficient to inhibit regeneration of female anterior fin regions. n = 16. Data are mean ± SD. p < 0.001 by two-tailed Student’s t test.

(C) Whole-mount images of TCFsiam; dkk1b:EGFP pectoral fins at 2 dpa. TCFsiam expression is detectable in female pectoral fin blastemas (bottom) and male pectoral fins (top, b). By contrast, TCFsiam expression is low or undetectable in anterior blastemas of male pectoral fins (top, a). Below the “Male” panel are enlargements of the boxed areas a and b. Panels at the bottom show enlargements of the boxed area in the “Female” panel directly above them. Scale bar, 500 μm.

(D) Section images showing stunted male pectoral fin regeneration at 2 dpa, with dkk1b:EGFP⁺ ETs within and just dorsal to the wound epidermis (asterisk). By 4 dpa, regenerates are dysmorphic, typically angling ventrally away from dkk1b:EGFP⁺ ETs before overcorrecting dorsally. Scale bar, 50 μm.