The Golgi stacks in the cytoplasts are polarized and transport cargo. (A–F) The Golgi in the cytoplasts is composed of polarized stacks. PtK1 cells stably expressing the medial/trans-Golgi enzyme NAGT I–GFP were induced to divide asymmetrically and followed by video microscopy. Upon division, cells were either processed for EM (A and B) or for immunofluorescence (C–F). (A and B) Stacked Golgi cisternae reformed in both karyoplasts (karyo; A) and cytoplasts (cyto; B). Bar, 200 nm. (C–F) The Golgi stacks are polarized. Divided cells were triple labeled with GFP, anti-GFP, and anti–cis-Golgi marker GM130. Two-channel overlays were performed as specified. GFP fluorescence is shown in green (C–F), and the antibody stainings for GFP (C and D) and GM130 (E and F) are pseudocolored in red. The GFP fluorescence colocalized with the anti-GFP signal (C and D) but only partially overlapped with the anti-GM130 signal (E and F) in both karyoplasts (C and E) and cytoplasts (D and F), as shown schematically in the insets. Bar, 2 µm. (G–N) CD8 transport assay. CD8 mRNA was microinjected into cells with asymmetrical monoasters together with Mad1 (G–J) or into the cytoplasts induced by Cdk1 inhibition (K–N). CD8 on the cell surface was stained before permeabilization (H and L). Note that CD8 was expressed and transported to the plasma membrane in the cytoplasts (asterisks). Karyoplasts are marked by arrows. Bar, 10 µm.