Fig. 4

Wnt8a overexpression induces the expression of various hepatic markers and represses the expression of an intestinal and a ventral pancreatic marker. Embryos obtained from outcrossing Tg(hs:wnt8a) zebrafish were heat-shocked at 26 hpf and harvested at 40 (I,J,M,N), 55 (A,B,K,L,O,P,S,T), 70 (Q,R) or 72 (C-H) hpf for in situ hybridization. (A-H) Wnt8a overexpression induced the expression of the hepatoblast marker hhex (B, n=10 out of 10), the hepatocyte markers cp (D, n=14 out of 14) and sepp1b (F, n=12 out of 14), and the hepatic ductal marker sox9b (H, n=13 out of 13) in the endoderm (brackets) posterior to the liver (arrows). Arrowheads indicate the dorsal pancreas (A,B). (I-P) By contrast, Wnt8a overexpression initially repressed the expression of the intestinal marker cdx1b (J, n=17 out of 17) and the early ventral pancreatic marker ptf1a (N, arrow, n=18 out of 18), but later their expression recovered (L,P), except for cdx1b expression in the intestinal bulb region (L, bracket, n=10 out of 10). Arrows in M-P point to the ventral pancreas or its progenitor cells. (Q-T) However, Wnt8a overexpression did not appear to affect the expression of other endodermal markers such as the swim bladder marker anxa5b (R, arrow, n=13 out of 13) or the thyroid marker nkx2.1a (T, arrow, n=10 out of 10). Arrows point to the swim bladder (Q,R) or thyroid (S,T). Dorsal (A-R) or side (S,T) views, anterior to the left. Scale bar: 100 μm.