(A) Claudin 3 is co-expressed with Pdx1 (arrow) in multipotent progenitors of E10.5 pancreata. (B) At this stage, claudin 3 (red; arrow) localizes to the lateral membrane of pancreatic cells. (C) At E12.5, following polarization of the pancreatic primordium, claudin 3 (red; arrows) co-localizes with ZO-1 (green) at tight junctions in primitive ducts. (D,E) Claudin 3 and ZO-1 coexpression is noticed towards the lumen of the emerging pancreatic ductal network at E15.5 (arrows in D), and in ductal epithelial cells at E18.5 (arrows in E). (F) Claudin 3 is expressed at high levels in ductal cells (Opn+ cells; arrows), and at lower levels in acinar cells (arrowhead), in P5 pancreata. (G,H) Claudin 3 co-localizes with ZO-1 in both ductal (arrows in G) and acinar (arrows in H) cells in P5 pancreata. Asterisk in G indicates an autofluorescent red blood cell. B–H are confocal images (cell nuclei were stained with DAPI [blue]). Scale bars: 25 μm (A), 20 μm (F), 10 μm (B–E,G), 5 μm (H).