Fig. 2

Fig. 2 ascl1a-/- 5 dpf embryos lack intestinal epithelial secretory cells. At 5 dpf WT embryos have a narrow diameter throughout the intestinal lumen (A). ascl1a-/- embryos (B) develop an increased luminal diameter in the proximal intestine (arrow), fail to completely utilize the yolk, and fail to inflate the swim bladder while the distal intestine appears normal. The 2F11 intestinal epithelial pan-secretory cell marker reveals numerous secretory cells distributed throughout the length of the 5 dpf intestine (C). Within ascl1a-/- 5 dpf embryos, secretory cells are absent throughout the entire intestine (D). In this preparation residual pancreatic cells are observed on the lateral side of the proximal intestine (arrow in (D) and region enlarged in (D′)). Markers for individual subtypes of secretory cells are also absent in the intestinal epithelium (only the distal intestine is shown in panels (E)–(H)). Goblet cells are distributed only throughout the distal WT intestine (E) as demonstrated by the fluorescently labeled lectin, wheat germ agglutinin but are absent from ascl1a-/- embryos (F). Serotonin (5HT) containing enterochromaffin cells are distributed only throughout the distal intestinal epithelium along with 5HT enteric neurons as demonstrated by anti-5HT immunohistochemistry (G). In ascl1a-/- embryos, enterochromaffin cells are absent; however, there are a few remaining 5HT enteric neurons (arrowheads (H)). Scale bar represents 100 μm.