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© The Rockefeller University Press,
0021-9525/1999//1 $5.00
The Journal of Cell Biology, Volume 146, Number 1,
, 1999 1-12
Original Article |
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
maro{at}ccr.jussieu.fr
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.
Key Words: meiosis microtubule kinetochore chromosome spindle assembly checkpoint
© 1999 The Rockefeller University Press
1.used in this paper: CLIP-170, cytoplasmic linker protein 170; GV, germinal vesicle; GVBD, germinal vesicle break down; MTOCs, microtubule organizing centers; PBE, polar body extrusionStéphane Brunet's present address is Cell Biology and Biophysics Programme, EMBL, Heidelberg, Germany; Denis Dujardin's present address is University of Massachusetts Medical School, Worcester, MA; and Jacek Kubiak's present address is Biologie et Génétique du Développement, UPR 41, CNRS, Rennes, France.
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