The spindle assembly checkpoint is not essential for CSF arrest of mouse oocytes.
In Xenopus oocytes, the spindle assembly checkpoint (SAC) kinase Bub1 is required for cytostatic factor (CSF)-induced metaphase arrest in meiosis II. To investigate whether matured mouse oocytes are kept in metaphase by a SAC-mediated inhibition of the anaphase-promoting complex/cyclosome (APC/C) complex, we injected a dominant-negative Bub1 mutant (Bub1dn) into mouse oocytes undergoing meiosis in vitro. Passage through meiosis I was accelerated, but even though the SAC was disrupted, injected oocytes still arrested at metaphase II. Bub1dn-injected oocytes released from CSF and treated with nocodazole to disrupt the second meiotic spindle proceeded into interphase, whereas noninjected control oocytes remained arrested at metaphase. Similar results were obtained using dominant-negative forms of Mad2 and BubR1, as well as checkpoint resistant dominant APC/C activating forms of Cdc20. Thus, SAC proteins are required for checkpoint functions in meiosis I and II, but, in contrast to frog eggs, the SAC is not required for establishing or maintaining the CSF arrest in mouse oocytes.
Tsurumi
Chizuko
C
Max-Planck-Institut fuer Immunbiologie, Developmental Biology, Freiburg, Germany. tsurumi@immunbio.mpg.de
Hoffmann
Steffen
S
Geley
Stephan
S
Graeser
Ralph
R
Polanski
Zbigniew
Z
D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins; D005260:Female; D064246:Mad2 Proteins; D008540:Meiosis; D051379:Mice; D008815:Mice, Inbred Strains; D009154:Mutation; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D017231:Proto-Oncogene Proteins c-mos / Q000378:metabolism / Q000502:physiology*; D008941:Spindle Apparatus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D013324:Strontium / Q000494:pharmacology; D043743:Ubiquitin-Protein Ligase Complexes / Q000037:antagonists & inhibitors / Q000502:physiology
C584278:Bub1b protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D064246:Mad2 Proteins; C577698:Mad2l1 protein, mouse; C577699:Mad2l2 protein, mouse; D009687:Nuclear Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D011494:Protein Kinases; C584281:Bub1 protein, mouse; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; D017231:Proto-Oncogene Proteins c-mos; D015739:Nocodazole; D013324:Strontium