Fig. 4

Morphogenesis of gastrointestinal tract mesenchyme in ihha^-/-. A, B, cross sections with H & E staining show gastrointestinal tract of control and mutant larvae at the level of anterior swimbladder. Red lines show the size of epithelial and mesenchymal layers. Dotted red lines show the size of the lumen with epithelial and mesenchymal (arrow) layers in control and mutant larvae at 74 hpf. Note slightly reduced epithelial and mesenchymal layers of the gut and gut lumen in the mutant. C–F, Expression of fgf10a is prominent in anterior gut of control and reduced in mutant at 74 hpf. E, F, Cross sections show strong expression of fgf10a in the mesenchyme of esophagus in controls and significantly reduced in the corresponding region of ihha^-/-. G, H, Expression of acta2 in the gastrointestinal tract mesenchyme. In ihha^-/- mutant this expression is missing. I, J, Cross-section of gastrointestinal tract at the level of the anterior part of swimbladder in controls and ihha^-/- reveals cell bodies of HuC/D-positive enteric neurons alongside of esophagus and intestine in controls and their absence in ihha^-/- mutant. Dotted white lines separate epithelium from mesenchyme. Abbreviations: e, epithelium; es, esophagus; en, enteric neurons; m, mesenchyme; l, liver; sb, swimbladder; n, notochord. Numbers represent somites. Scale bars: 250 μm.