Figure 3. Induction of de novo ET Formation by Androgen and Wnt Signaling.

(A) Section images of the dorsal side of a female pectoral fin after the indicated duration of androgen treatment. Dashed lines indicate the outer epidermal border (Left and Middle) or individual ET (Right). Note that local epidermal thickening is observed by 2 dpt.

(B, C) Whole-mount (B) and section (C) images of female TCFsiam; dkk1b:EGFP pectoral fins after 2 days of androgen treatment. Arrows indicate dkk1b:EGFP expression in basal layers in forming ET. Dotted line outlines an ET precursor with one middle cell expressing weak TCFsiam.

(D, E) Whole-mount (D) and section (E) images of female TCFsiam;dkk1b:EGFP pectoral fins after 7 days of androgen treatment. ET show stage-specific expression profiles. Putative newly forming ET express TCFsiam (Class I, arrow). Putative immature ET show both TCFsiam and dkk1b:EGFP expressions (Class II, asterisks). Mature ET express only dkk1b:EGFP or both TCFsiam and dkk1b:EGFP (Class III, arrowheads). Note that TCFsiam expression is weak in mature ET.

(F) LiCl treatment increases ET formation in androgen-treated adult females. Data are mean ± standard deviation (s.d.), **P < 0.05 by two-tailed Student’s t-test

(G, H) Ubiquitous overexpression of dkk1b blunts ET formation in androgen-treated adult females (G) and juvenile males (H). Arrows indicate developing ET in (G). Data are mean ± s.d., *P < 0.001 by two-tailed Student’s t-test

Scale bars = 10 μm (A, C); 50 μm (E). See also Figure S2.