Fig. 1. Bmp signaling is essential for hepatoblast specification. Embryos obtained from outcrossing a hemizygous Tg(hsp70l:dnBmpr-GFP) zebrafish were heat shocked at 18 hpf, and harvested at 29-32 (A-O) or 38-40 (P,Q) hpf. The expression of hhex (A-C), prox1 (D-F), gata4 (G-I), gata6 (J-L), foxa3 (M-O) and ceruloplasmin (cp) (P,Q) was then examined by in situ hybridization. The percentage of hemizygous embryos exhibiting a similar expression pattern is indicated in the lower left corner (n=8-10). (A-C) hhex expression in the liver region (arrows) was greatly reduced or almost absent in the hemizygous embryos, whereas its expression in the pancreatic islet (arrowheads) appeared unaffected. (D-F) prox1 expression in the liver region (arrows) was greatly reduced or almost absent in the hemizygous embryos, whereas its expression in the interrenal primordium (arrowheads) was less affected. To better visualize hepatic prox1 expression, a side-view image is shown in an inset. (G-L) gata4 and gata6 expression was reduced in the liver region (arrows), whereas their expression in the intestinal endoderm was barely affected (brackets). (M-O) The leftward bending of the gut, revealed by foxa3 expression, was often defective in the hemizygous embryos (brackets). (P,Q) Hepatocyte expression of cp was absent in the hemizygous embryos. All images, except insets, are dorsal views, anterior left.