Kinetochore fibers are not involved in the formation of the first meiotic spindle in mouse oocytes, but control the exit from the first meiotic M phase.
During meiosis, two successive divisions occur without any intermediate S phase to produce haploid gametes. The first meiotic division is unique in that homologous chromosomes are segregated while the cohesion between sister chromatids is maintained, resulting in a reductional division. Moreover, the duration of the first meiotic M phase is usually prolonged when compared with mitotic M phases lasting 8 h in mouse oocytes.We investigated the spindle assembly pathway and its role in the progression of the first meiotic M phase in mouse oocytes. During the first 4 h, a bipolar spindle forms and the chromosomes congress near the equatorial plane of the spindle without stable kinetochore- microtubule end interactions. This late prometaphase spindle is then maintained for 4 h with chromosomes oscillating in the central region of the spindle. The kinetochore-microtubule end interactions are set up at the end of the first meiotic M phase (8 h after entry into M phase). This event allows the final alignment of the chromosomes and exit from metaphase. The continuous presence of the prometaphase spindle is not required for progression of the first meiotic M phase. Finally, the ability of kinetochores to interact with microtubules is acquired at the end of the first meiotic M phase and determines the timing of polar body extrusion.
Laboratoire de Biologie Cellulaire du Développement, Université Paris 6, Paris, France.
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S
Brunet
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Maria
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P
Guillaud
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Dujardin
J Z
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Kubiak
B
B
Maro
D000818:Animals; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002875:Chromosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D007700:Kinetics; D018386:Kinetochores / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008540:Meiosis / Q000187:drug effects; D008677:Metaphase / Q000187:drug effects; D051379:Mice; D008854:Microscopy, Electron; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009363:Neoplasm Proteins; D015739:Nocodazole / Q000494:pharmacology; D009865:Oocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis; D011691:Puromycin / Q000494:pharmacology; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
D002843:Chromatin; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; C076744:cytoplasmic linker protein 170; D011691:Puromycin; D015739:Nocodazole