title: Synchronized shift in localization of the Golgi complex and the microtubule organizing center in the terminal phase of cytokinesis.
abstract: As mammalian cells enter mitosis, the Golgi complex is disorganized and the remnants are dispersed throughout the cytoplasm in the form of a few short cisternae and small clusters of vesicles. Once the separation of the chromosomes is completed and nuclei reform, stacks of flattened cisternae reappear and a united Golgi complex of interphase type starts to be reorganized. This process is believed to ensure an approximately equal partitioning of the Golgi complex on the daughter cells. Here, the configuration of the Golgi complex and its relation to the cytoplasmic microtubule system was studied at the end of cytokinesis using synchronized cultures of L929 mouse fibroblasts and rat dermal fibroblasts. One hour after the release of the mitotic block, the Golgi complex (visualized immunocytochemically with antibodies against mannosidase II) was most frequently located on the proximal side of the nucleus as related to the intercellular bridge (visualized immunocytochemically with antibodies against tyrosinated alpha-tubulin). One hour later, it was preferentially found on the distal side of the nucleus as related to the intercellular bridge. Immunocytochemical demonstration of the radiating pattern of microtubules, and direct demonstration of the centrioles using antibodies against detyrosinated or acetylated alpha-tubulin, showed that the microtubule organizing center (MTOC) shifted position in a similar manner as the Golgi complex. Moreover, double staining with antibodies against mannosidase II and tyrosinated alpha-tubulin revealed that the Golgi complex and the MTOC codistributed at both times after the release of the mitotic block. Electron microscopic analysis confirmed that the reforming Golgi stacks first gathered close to the centrosome (a pair of centrioles with associated structures, constituting the main MTOC in the cell) on the proximal side of the nucleus and that the Golgi stacks and the centrosome were subsequently both relocated to the distal side of the nucleus as related to the intercellular bridge. Taken together, the findings indicate that the Golgi complex goes through a characteristic translocation in the terminal phase of cytokinesis and confirm the idea that the cytoplasmic microtubule system plays an important role in the organization of this organelle system. A possible function of the shift in location of the Golgi complex at the end of cytokinesis could be to direct membrane traffic first to the elongating intercellular bridge and thereafter to the leading edge as the cells are about to separate and move away from each other.
authors.affiliation: Department of Medical Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Moskalewski
authors.forename: J
authors.initials: J
authors.lastname: Thyberg
mesh_terms: D000818:Animals; D002455:Cell Division; D002460:Cell Line; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure*; D007150:Immunohistochemistry; D051379:Mice; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure*; D015739:Nocodazole; D051381:Rats; D014404:Tubulin / Q000032:analysis
chemical_list: D014404:Tubulin; D015739:Nocodazole