Figure 12. Expression and subcellular localization of ZO-3 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 ZO-3 (A) or double labeled for ZO-3 and ZO-1 (B). Under standard optics (A), ZO-3 was observed along the lateral membranes in each culture. There was no apparent effect by rcSF3 on the distribution of ZO-3. Confocal microscopy (B) revealed the distribution of ZO-3 and ZO-1 in the XZ plane. ZO-3 colocalized with ZO-1 in a junctional complex at the apical end of the lateral membranes. In (B), arrowheads that point up indicate basal membrane, while arrowheads that point down mark apical membrane. The scale bar represents 10 μm.