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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.

Brunet S, Maria AS, Guillaud P, Dujardin D, Kubiak JZ, Maro B - J. Cell Biol. (1999)

Bottom Line: 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.This event allows the final alignment of the chromosomes and exit from metaphase.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Biologie Cellulaire du Développement, Université Paris 6, Paris, France.

ABSTRACT
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.

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Chromosome movements after removal of the nocodazole 8 h after GVBD. Pictures were taken every 3 min.
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Figure 8: Chromosome movements after removal of the nocodazole 8 h after GVBD. Pictures were taken every 3 min.

Mentions: This result was reinforced by live observation of chromosome movements after nocodazole treatment. In the NZ/3h–5h group, chromosomes kept oscillating near the equatorial plane until metaphase, as in untreated oocytes (not shown). In the NZ/6h–8h group, some individual chromosomes were observed moving towards the poles (Fig. 8, Fig. 010Fig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6 min) and then congressing to the equatorial plane (Fig. 8, Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10 min). Anaphase occurred after the alignment of the last chromosome (Fig. 8, 48 min).


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.

Brunet S, Maria AS, Guillaud P, Dujardin D, Kubiak JZ, Maro B - J. Cell Biol. (1999)

Chromosome movements after removal of the nocodazole 8 h after GVBD. Pictures were taken every 3 min.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199729&req=5

Figure 8: Chromosome movements after removal of the nocodazole 8 h after GVBD. Pictures were taken every 3 min.
Mentions: This result was reinforced by live observation of chromosome movements after nocodazole treatment. In the NZ/3h–5h group, chromosomes kept oscillating near the equatorial plane until metaphase, as in untreated oocytes (not shown). In the NZ/6h–8h group, some individual chromosomes were observed moving towards the poles (Fig. 8, Fig. 010Fig. 1Fig. 2Fig. 3Fig. 4Fig. 5Fig. 6 min) and then congressing to the equatorial plane (Fig. 8, Fig. 6Fig. 7Fig. 8Fig. 9Fig. 10 min). Anaphase occurred after the alignment of the last chromosome (Fig. 8, 48 min).

Bottom Line: 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.This event allows the final alignment of the chromosomes and exit from metaphase.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.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Biologie Cellulaire du Développement, Université Paris 6, Paris, France.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus