Fig. 6. Fgf signaling is essential for hepatoblast specification. Embryos obtained from outcrossing a hemizygous Tg(hsp70l:dnfgfr1-EGFP) zebrafish were heat shocked at 18 hpf, harvested at 29-31 (A-N) or 38-40 (O,P) hpf, and examined for hhex (A-C), prox1 (D,E), gata4 (F-H), gata6 (I-K), foxa3 (L-N) and cp (O,P) expression. 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 appeared unaffected (arrowheads). (D,E) prox1 expression in the liver region (arrows) was almost absent in the hemizygous embryos, whereas its expression in the interrenal primordium was less affected (arrowheads). To better visualize hepatic prox1 expression, a side-view image is shown in an inset. (F-K) gata4 and gata6 expression was greatly reduced in the liver region (arrows), whereas their expression in the intestinal endoderm was less affected (brackets). (L-N) The leftward bending of the gut did not occur in the hemizygous embryos (brackets). (P) Hepatocyte expression of cp was absent in the hemizygous embryos. All images, except insets, are dorsal views, anterior left.