Fig. 3. PATJ KD cells are polarized and establish tight junctions. (A) Confocal microscopic Z-sections of Control (CT Cl 8 and Cl 5) and PATJ KD clone (Cl 4 or 12) Caco2 cells grown on filters and labeled with affinity-purified antibodies against aPKC, E-cadherin (E-Cad), DPPIV or ZO-1. All markers are still properly localized on the lateral membrane (arrows) or the apical membrane or tight junctions (arrowheads), respectively. Under our staining conditions ZO-1 is also found in the cytoplasm of Caco2 cells. (B) Control Cl 8 and PATJ KD Cl 4 of Caco2 cells were seeded on filters and the TER was measured after 1, 2, 3 or 4 days of culture. Each point represents the average of five filters (bars indicate s.d.). No significant difference was observed between control and KD PATJ cells. (C) Electron microscopic views of the tight junction region of PATJ KD (a,b) and control cells (c) showing that no morphological differences in the organization of tight junctions (TJ), adherens junctions (AJ) and desmosomes (D) could be detected at this level of resolution. ap, apical cell surface; mv, microvilli. Bars, 10 µm (A,B); 100 nm (C,D).