IFT20 and Rab8 concentrate at peripheral and central structures in nonciliated MDCK cells. (A and B) EM micrographs showing three representative examples of PCs (A) and apical centrosomes (B). No ciliary pocket (A) or vesicles surrounding the centrosome (B) were observed in 14 cilia and 16 apical centrosomes examined, respectively. The arrowhead marks the centrosome. Bars, 500 nm. (C–E) Cells grown for 4 d were stained for IFT20 and α-tubulin (C), Rab8 and IFT20 (D), and podocalyxin and α-tubulin (α-tub; E). The position of the centrosome was monitored by expression of dsRed-centrin. The projection of one to three apical planes of one representative example of each of the distributions patterns is shown. The dashed line indicates the cell contour. The enlargement shows the fluorescent signal in the boxed region for the proteins analyzed. White arrowheads point to the centrosome or to each of the two centrioles if they are separated, and green arrowheads point to the peripheral and central structures. Bars, 2 µm. (F) The number of cells with peripheral or central structures or a PC was measured at the indicated times after cell plating. Each dot represents the result from a microscope field. Three independent experiments were performed (n = 207–847 cells per time point; two to five fields per time point and per experiment).