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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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Characterization of CLIP-170 in mouse oocytes. CLIP-170 appears in green and chromosomes in red. 10–15 optical sections were merged for the final images. CLIP-170 staining during the metaphase II arrest (A). Oocytes were cultured in the presence of 10 μg/ml nocodazole for 1 h and fixed immediately (B), 15 min (C), and 30 min (D) after removal of the drug.
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Figure 5: Characterization of CLIP-170 in mouse oocytes. CLIP-170 appears in green and chromosomes in red. 10–15 optical sections were merged for the final images. CLIP-170 staining during the metaphase II arrest (A). Oocytes were cultured in the presence of 10 μg/ml nocodazole for 1 h and fixed immediately (B), 15 min (C), and 30 min (D) after removal of the drug.

Mentions: CLIP-170 is associated with kinetochores during prometaphase in somatic cells (Dujardin et al. 1998) until the formation of kinetochore fibers (Dujardin, D., and J. de Mey, manuscript in preparation). We first checked whether this was the case in mouse oocytes. In metaphase II-arrested oocytes, kinetochore fibers are present and no CLIP-170 staining was observed on the chromosomes (Fig. 5 A). After total depolymerization of microtubules by 10 μg/ml nocodazole, CLIP-170 staining was observed on kinetochores (Fig. 5 B). This staining disappeared rapidly when microtubules polymerized after nocodazole removal (Fig. 5C and Fig. D). Thus, in mouse oocytes, CLIP-170 behaves as it does in somatic cells: it is associated with kinetochores in the absence of kinetochore fibers.


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)

Characterization of CLIP-170 in mouse oocytes. CLIP-170 appears in green and chromosomes in red. 10–15 optical sections were merged for the final images. CLIP-170 staining during the metaphase II arrest (A). Oocytes were cultured in the presence of 10 μg/ml nocodazole for 1 h and fixed immediately (B), 15 min (C), and 30 min (D) after removal of the drug.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: Characterization of CLIP-170 in mouse oocytes. CLIP-170 appears in green and chromosomes in red. 10–15 optical sections were merged for the final images. CLIP-170 staining during the metaphase II arrest (A). Oocytes were cultured in the presence of 10 μg/ml nocodazole for 1 h and fixed immediately (B), 15 min (C), and 30 min (D) after removal of the drug.
Mentions: CLIP-170 is associated with kinetochores during prometaphase in somatic cells (Dujardin et al. 1998) until the formation of kinetochore fibers (Dujardin, D., and J. de Mey, manuscript in preparation). We first checked whether this was the case in mouse oocytes. In metaphase II-arrested oocytes, kinetochore fibers are present and no CLIP-170 staining was observed on the chromosomes (Fig. 5 A). After total depolymerization of microtubules by 10 μg/ml nocodazole, CLIP-170 staining was observed on kinetochores (Fig. 5 B). This staining disappeared rapidly when microtubules polymerized after nocodazole removal (Fig. 5C and Fig. D). Thus, in mouse oocytes, CLIP-170 behaves as it does in somatic cells: it is associated with kinetochores in the absence of kinetochore fibers.

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