Behavior of delta-tubulin during spindle formation in Xenopus oocytes: requirement of cytoplasmic dynein-dependent translocation.
Vertebrate oocytes do not contain centrosomes and therefore form an acentrosomal spindle during oocyte maturation. gamma-Tubulin is known to be essential for nucleation of microtubules at centrosomes, but little is known about the behaviour and role of gamma-tubulin during spindle formation in oocytes. We first observed sequential localization of gamma-tubulin during spindle formation in Xenopus oocytes. gamma-Tubulin assembled in the basal regions of the germinal vesicle (GV) at the onset of germinal vesicle breakdown (GVBD) and remained on the microtubule-organizing centre (MTOC) until a complex of the MTOC and transient-microtubule array (TMA) reached the oocyte surface. Prior to bipolar spindle formation, oocytes formed an aggregation of microtubules and gamma-tubulin was concentrated at the centre of the aggregation. At the late stage of bipolar spindle formation, gamma-tubulin accumulated at each pole. Anti-dynein antibody disrupted the localization of gamma-tubulin, indicating that the translocation described above is dependent on dynein activity. We finally revealed that XMAP215, a microtubule-associated protein cooperating with gamma-tubulin for the assembly of microtubules, but not gamma-tubulin, was phosphorylated during oocyte maturation. These results suggest that gamma-tubulin is translocated by dynein to regulate microtubule organization leading to spindle formation and that modification of the molecules that cooperate with gamma-tubulin, but not gamma-tubulin itself, is important for microtubule reorganization.
Kotani
Tomoya
T
Laboratory of Molecular and Cellular Interactions, Division of Biological Sciences, Graduate School of Science, Hokkaido University, Japan. tkotani@lab.nig.ac.jp
Yamashita
Masakane
M
D000818:Animals; D018385:Centrosome / Q000502:physiology; D004398:Dyneins / Q000276:immunology / Q000378:metabolism; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000276:immunology / Q000378:metabolism*; D009865:Oocytes / Q000254:growth & development*; D009866:Oogenesis; D010766:Phosphorylation; D008941:Spindle Apparatus / Q000502:physiology*; D014404:Tubulin / Q000378:metabolism*; D029867:Xenopus Proteins / Q000276:immunology / Q000378:metabolism*; D014982:Xenopus laevis / Q000502:physiology*
C486738:CKAP5 protein, Xenopus; D008869:Microtubule-Associated Proteins; D014404:Tubulin; D029867:Xenopus Proteins; D004398:Dyneins