Fig. 8

Mutations affecting early stages of exocrine pancreas development on 4 dpf. Right lateral view of live wild type (A), slj (B), pie (C) and flo (D) larvae. In the wild type larva (A), the intestinal epithelium is folded, only a small amount of yolk is evident, and the swim bladder is inflated. By comparison, the intestines in slj (B), pie (C) and flo (D) are narrow, and they lack folds. (E–H) Histological cross-sections through the exocrine pancreas 3 μm caudal to the islet. Wild type acinar cells contain zymogen granules (E, red arrows), whereas in slj (F), pie (G) and flo (H), the pancreatic cells lack zymogen granules. (I–L) Dorsal view of larvae processed for whole mount RNA in situ hybridization using an antisense trypsin probe. Strong trypsin expression is present in the wild type larva (I), whereas in slj (J), pie (K) and flo (L) larvae, there is reduced trypsin expression. Arrows point at pancreatic head and pancreatic tail. (M–P) Wild type and mutant pancreata processed for whole mount cyk and cpa immunohistochemistry (IHC). The wild type exocrine pancreas (M) is comprised of cpa+ acinar cells and a network of cyk+ ducts that joins the extrapancreatic main duct. The exocrine pancreata of slj (N), pie (O) and flo (P) larvae are small. The extrapancreatic duct can be identified, but there is no significant cpa detected, and only a small number of ducts are recognizable. (Q–T) Confocal analysis of pancreatic ducts following cyk IHC. Ducts in the mutant pancreata resemble primary ducts seen in wild type larvae (Figs. 4C, G). (U–X) Histological cross-sections through the pancreas ∼3 μm posterior to the islet of larvae processed for cyk IHC merged with bright field images of the corresponding histological sections stained with methylene blue and azure II. Small ducts are evident in the wild type larva (U; arrowheads) and in slj (V), pie (W) and flo (X) larvae). slj: slimjim; pie: piebald; flo: flotte lotte; e: exocrine pancreas; in: intestine; cyk: cytokeratin; cpa: carboxypeptidase A; epd: extrapancreatic main duct.