Fig. 3

Elevated Wnt signaling in melanocyte differentiation time window alters melanocyte morphology. (A) Schematic of melanocyte differentiation BIO treatment time windows. (B–E) Activation of Wnt signaling in early differentiation period (24–48 hpf) increases melanocyte dendricity and dispersion. Lateral view at 48 hpf of head of live embryos treated with control DMSO (B) or BIO (C) from 24 to 48 hpf. Panels D and E show enlargements of head melanocytes from embryos in B and C, respectively. (F) Quantitation of dendricity: the cell roundness parameter was calculated for each melanocyte as R = P2 ⁄ 4∏A, where A is the cell area and P the cell perimeter, and 20 cells were investigated (n = 20) in 10 different embryos for each condition. A score of R = 1.0 represents a perfectly round melanocyte; increased R values represent increased dendricity. Control, R = 2.44 ± 0.43, BIO R = 4.25 ± 1.68, P = 0.004, t test result, P-value < 0.01 (**). (G–J) Elevated Wnt signaling throughout full differentiation or during late differentiation window only affects melanocyte organization. Red line in G indicates the dorsal head melanophores which usually approximate an O- or U-shaped pattern, although often with extra branches as in this specific example. Dorsolateral view at 72 hpf of heads of live embryos treated with control DMSO (G, I, K, M) or BIO (H, J, L, N) from 24 to 72 hpf shown. Note that embryos treated in only late differentiation window (48–72 hpf) show equivalent phenotype (data not shown). Embryos shown are representative of samples examined (n = 160 zebrafish embryos for each treatment). Scale bars: 100 μm (B, D, G, I).