Fig. 5
The extent of the endodermal region retaining hepatic competence is gradually reduced with time. (A-F) Embryos obtained from crossing wnt2bb-/- with Tg(hs:wnt8a);wnt2bb-/- zebrafish were heat-shocked at 22 (A,B), 30 (C,D) or 34 (E,F) hpf, and harvested at 70-74 hpf for whole-mount immunostaining. The Tg(fabp10:dsRed,ela3l:EGFP) line was used to reveal hepatocytes (red) and pancreatic acinar cells (green); mAb 2F11 staining reveals the hepatopancreatic duct (blue). Wnt8a overexpression at 22 hpf (B, bracket, n=6 out of 6) induced more ectopic hepatocytes than at 30 hpf (D, brackets, n=14 out of 14); Wnt8a overexpression at 34 hpf failed to induce ectopic hepatocytes (F, n=6 out of 6). However, the liver size in wnt2bb mutants increased even when Wnt8a was overexpressed at 34 hpf. Ventral views, anterior up. Scale bars: 50 μm. |