Morphogenesis of the gastrointestinal epithelium in ihha-/- mutant. A, B, Expression of endodermal marker gata6 at 32 hpf. C, D, Expression of foxa1 along the pharynx, esophagus, intestina, swimbladder and liver epithelium at 50 hpf. Note a reduced endoderm in the absence of Ihha signaling. E, F, At 60 hpf foxa2 is expressed in the pharynx, esophagus, swimbladder, pneumatic duct, intestine, and floor plate. foxa2 expression is not affected along the floor plate in ihha-/- mutant, but reduced in endodermal domains, A–F, whole mount. G, H, Cross sections of foxa2 expression revealed reduced epithelium of the intestine and swimbladder in ihha-/- compared to control embryos at 60 hpf. I, J, Expression of the enterocyte marker ifabp along gastrointestinal tract is altered in ihha-/- at 74 hpf. K, L, In control larvae strong expression of ifabp is in the apical aspect of the gastrointestinal epithelium demonstrating epithelial differentiation, which is less obvious in ihha-/-. Abbreviations: e, epithelium; L, liver; ph, pharynx; pd, pneumatic duct; es, esophagus; g, gut; ph, pharynx; s, somites; sb, swimbladder; n, notochord. Numbers represent anterior somites. Scale bars: 250 μm.