Figure 11. Expression and subcellular localization of claudin 20 in culture. RPE was isolated from E7 or E14 embryos and cultured with SF2 in the basal medium chamber and either SF3 or rcSF3 in the apical medium chamber. The cultures were labeled for claudin 20 (A) or double labeled for claudin 20 and ZO-1 (B). Under standard optics (A), claudin 20 was observed along the lateral membranes in each culture. When E7 RPE was cultured with SF3 in the apical medium chamber, a vesicular distribution was less evident when the RPE was cultured with rcSF3 in the apical medium chamber. Confocal microscopy (B) revealed the distribution of claudin 20 and ZO-1 in the XZ plane. Claudin 20 colocalized with ZO-1 in a junctional complex at the apical end of the lateral membranes, as indicated by the yellow in the merged image. In (B), arrowheads that point up indicate basal membrane, while arrowheads that point down mark apical membrane. The scale bar represents 10 μm.