Fig. 4

HDACs are required for early liver development. Expressions of early liver markers were analyzed by WISH in WT and VPA-treated embryos including hhex (A–D, K, L), prox1 (E–H, M, N) and foxa3 (I, J, O, P). All panels are whole mount pictures except panels B, D, F and H which are tissue sections corresponding to panels A, C, E and G, respectively, with section planes indicated by red lines. In all panels, liver is indicated by a thick white arrow while pancreas is indicated by a thick black arrow. Expression of hhex was completely abolished in liver and pancreatic islet (C vs. A) at 24 hpf in VPA-treated embryos while its expression in intermediate cell mass (ICM) (A vs. C, thin black arrow) remains unaffected. Note that panels A and C were focused on different focal planes with panel A focusing on the liver region while panel C focusing on the more posterior ICM. White arrowhead indicates hhex expression in notochord (A–D) and black arrowhead in panels C and D refers to hhex expression in anterior endoderm. At 48 hpf, hhex expression in liver and pancreatic islet was significantly reduced (K vs. L). prox1 expression in liver region was absent in treated embryos at 28–30 hpf (E vs. G, F vs. H) while its expression was greatly reduced at 48 hpf (M vs. N). The green arrowhead in panel E indicates interregnal gland which also expresses prox1 at this stage. Initial endoderm thickening at liver region was absent in treated embryos at 28–30 hpf as judged by foxa3 expression (I vs. J, white arrow). At 48 hpf, a slightly small and compressed liver was observed in VPA-treated embryos while the hepatic duct was still not well formed (O vs. P, thin green arrow). All imagines are dorsal view, anterior to the left. Scale bar represents 100 μm in panels A, C, E, G, I and J; 20 μm in panels B, D, F and H; 50 μm in panels K–P. Lv: liver; Pn: pancreas; in: intestine; Sb: swim bladder.