Fig. 9. Jagged-mediated Notch signaling regulates pancreatic duct development. Confocal projections through the posterior pancreas of 5-dpf wild-type (A,C,E) and jagged 2/3 morphant (B,D,F,I) larvae processed for cytokeratin IHC (green; duct marker), and carboxypeptidase (red; acinar cell marker) IHC. (A) Immunoreactive cytokeratin outlines ducts within the wild-type pancreas (arrow), as well as a large ventral blood vessel (^*). (B) Only a few large ducts (arrowheads) are visible in jagged 2/3 morphants. Most regions of the morphant pancreas are devoid of ducts and instead contain enlarged acini (arrows) that ectopically express cytokeratin. Acinar structure in morphant larvae was confirmed ultrastructurally (not shown). (C) Immunoreactive carboxypeptidase A (red) is localized in small acini in the wild-type pancreas. (D) Acini in 5-dpf jagged 2/3 morphants are enlarged (arrows) and may have dilated lumens (lower arrow). Acinar cells express carboxypeptidase A (red). (E,F) Superimposed confocal projections through wild-type and jagged 2/3 morphant pancreas shown in A and C, and B and D, respectively. The acinar cells within the enlarged morphant acini (arrows in F) ectopically express the cytokeratin duct marker on the apical and lateral cell surface of the acinar cells. (I) Thin optical section (10 µm) through the lumen of the larger acinus depicted in B and F, showing apical cytokeratin in cells lining the acinar lumen (arrow). (G,H) Low power, whole-mount image of the 5-dpf wild-type (G) and jagged 2/3 morphant (H) larval pancreas; larvae processed for carboxypeptidase A IHC (green). Note the enlarged, dispersed acini in the jagged 2/3 larvae (H) compared with wild-type sibling (G).