The Golgi in the karyoplasts but not in the cytoplasts reforms a ribbon. (A) Diagram of the assay. PtK1 cells stably expressing NAGT I–GFP were treated with an Eg5 inhibitor (monastrol or trityl-cysteine) for 2 h to induce asymmetrically positioned monoasters. Cell division was triggered either by microinjection of Mad1 or by addition of a Cdk1 inhibitor (purvalanol A or roscovitine), leading to a karyoplast that received the entire spindle (centrosomes, chromosomes, and spindle microtubules) and a cytoplast that lacked all of these. (B–I) Divided cells were either identified by the injection marker (B; Mad1 injection) or followed by time-lapse phase-contrast microscopy (F; Cdk1 inhibition). Cells were stained for GFP (C and G), tubulin (D and H), and DNA (E and I). The Golgi in the karyoplasts (arrows) reformed a characteristic ribbon in the perinuclear region, whereas the Golgi in the cytoplasts (asterisks) was scattered throughout the cytoplasm (C and G). In addition, no microtubule (MT) network was present in the cytoplasts (D and H). Bar, 10 µm.