Fig. 2. Alk8 is required for early liver development. Wild-type and alk8 mutant zebrafish embryos at 26 (A-H), 28 (I,J) and 48 (K,L) hpf were analyzed for hhex (A,B), prox1 (C,D), gata4 (E,F), gata6 (G,H), foxa3 (I,J) and cp (K,L) expression. (A,B) hhex expression in the liver region (arrows) is greatly reduced in the mutants, whereas its expression in the pancreatic islet appears unaffected (arrowheads). (C,D) prox1 expression in the liver region (arrows) is also greatly reduced in the mutants, whereas its expression in the interrenal primordium appears unaffected (arrowheads). To better visualize hepatic prox1 expression, a side-view image is shown in an inset. (E-H) gata4 and gata6 expression is reduced in the liver region (arrows), whereas their expression in the intestinal endoderm is only mildly affected (brackets). (I,J) The leftward bending of the gut appears unaffected in the mutants (brackets). (K,L) Hepatocyte expression of cp is completely absent in the mutants. All images, except insets, are dorsal views, anterior left.