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Spindle assembly and cytokinesis in the absence of chromosomes during Drosophila male meiosis.

Bucciarelli E, Giansanti MG, Bonaccorsi S, Gatti M - J. Cell Biol. (2003)

Bottom Line: The cells containing chromosome-free spindles are also able to assemble regular cytokinetic structures and cleave normally.In addition, chromosome-free spindles normally accumulate the Aurora B kinase at their midzones.This suggests that the association of Aurora B with chromosomes is not a prerequisite for its accumulation at the central spindle, or for its function during cytokinesis.

View Article: PubMed Central - PubMed

Affiliation: Istituto Pasteur Fondazione Cenci Bolognetti, 00185 Rome, Italy.

ABSTRACT
A large body of work indicates that chromosomes play a key role in the assembly of both a centrosomal and centrosome-containing spindles. In animal systems, the absence of chromosomes either prevents spindle formation or allows the assembly of a metaphase-like spindle that fails to evolve into an ana-telophase spindle. Here, we show that Drosophila secondary spermatocytes can assemble morphologically normal spindles in the absence of chromosomes. The Drosophila mutants fusolo and solofuso are severely defective in chromosome segregation and produce secondary spermatocytes that are devoid of chromosomes. The centrosomes of these anucleated cells form robust asters that give rise to bipolar spindles that undergo the same ana-telophase morphological transformations that characterize normal spindles. The cells containing chromosome-free spindles are also able to assemble regular cytokinetic structures and cleave normally. In addition, chromosome-free spindles normally accumulate the Aurora B kinase at their midzones. This suggests that the association of Aurora B with chromosomes is not a prerequisite for its accumulation at the central spindle, or for its function during cytokinesis.

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Aurora B distribution in wild-type and fsl spermatocytes. Cells were stained for tubulin (green), Aurora B (orange), and DNA (blue). (a) Wild-type metaphase I; (b) fsl metaphase I; (c) Wild-type telophase I; (d) fsl telophase I; (e) Chromosome-free fsl early telophase II; (f) Chromosome-free fsl late telophase II. Note that Aurora B concentrates in the central spindle midzone in the absence of chromosomes. Bar, 10 μm.
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fig4: Aurora B distribution in wild-type and fsl spermatocytes. Cells were stained for tubulin (green), Aurora B (orange), and DNA (blue). (a) Wild-type metaphase I; (b) fsl metaphase I; (c) Wild-type telophase I; (d) fsl telophase I; (e) Chromosome-free fsl early telophase II; (f) Chromosome-free fsl late telophase II. Note that Aurora B concentrates in the central spindle midzone in the absence of chromosomes. Bar, 10 μm.

Mentions: To further characterize the central spindles of chromosome-free spermatocytes, we asked whether they have the ability to bind Aurora B. Aurora B is in an evolutionary conserved macromolecular complex that contains the inner centromere protein and survivin (for review see Adams et al., 2001). The proteins of this complex are called chromosome passengers (Earnshaw and Bernat, 1991) because they accumulate at centromeres in metaphase, but move to the central spindle midzone in telophase. Given that both Aurora B and the inner centromere protein are essential for cell cleavage, it has been suggested that these proteins may help to integrate chromosomal events with cytokinesis (Adams et al., 2001). Immunostaining of wild-type spermatocytes for Aurora B showed that this protein is concentrated at metaphase kinetochores (Fig. 4 a). As spermatocytes progress through cell division, Aurora B accumulates in the central spindle midzone (Fig. 4 c). In chromosome-containing cells of fsl and suo mutants, Aurora B behavior is identical to wild type (Fig. 4 b and d; unpublished data). In chromosome-free metaphase-like figures from both fsl and suo mutants, Aurora B displays a diffuse staining (unpublished data). However, as these cells move toward telophase, Aurora B accumulates in the central spindle midzone, as occurs in wild type (Fig. 4, e and f). Together, these results clearly show that Aurora B concentration in the central spindle does not require its previous localization at kinetochores. In addition, they strongly suggest that the role played by Aurora B during cytokinesis is independent of that played in chromosome structure and segregation.


Spindle assembly and cytokinesis in the absence of chromosomes during Drosophila male meiosis.

Bucciarelli E, Giansanti MG, Bonaccorsi S, Gatti M - J. Cell Biol. (2003)

Aurora B distribution in wild-type and fsl spermatocytes. Cells were stained for tubulin (green), Aurora B (orange), and DNA (blue). (a) Wild-type metaphase I; (b) fsl metaphase I; (c) Wild-type telophase I; (d) fsl telophase I; (e) Chromosome-free fsl early telophase II; (f) Chromosome-free fsl late telophase II. Note that Aurora B concentrates in the central spindle midzone in the absence of chromosomes. Bar, 10 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172764&req=5

fig4: Aurora B distribution in wild-type and fsl spermatocytes. Cells were stained for tubulin (green), Aurora B (orange), and DNA (blue). (a) Wild-type metaphase I; (b) fsl metaphase I; (c) Wild-type telophase I; (d) fsl telophase I; (e) Chromosome-free fsl early telophase II; (f) Chromosome-free fsl late telophase II. Note that Aurora B concentrates in the central spindle midzone in the absence of chromosomes. Bar, 10 μm.
Mentions: To further characterize the central spindles of chromosome-free spermatocytes, we asked whether they have the ability to bind Aurora B. Aurora B is in an evolutionary conserved macromolecular complex that contains the inner centromere protein and survivin (for review see Adams et al., 2001). The proteins of this complex are called chromosome passengers (Earnshaw and Bernat, 1991) because they accumulate at centromeres in metaphase, but move to the central spindle midzone in telophase. Given that both Aurora B and the inner centromere protein are essential for cell cleavage, it has been suggested that these proteins may help to integrate chromosomal events with cytokinesis (Adams et al., 2001). Immunostaining of wild-type spermatocytes for Aurora B showed that this protein is concentrated at metaphase kinetochores (Fig. 4 a). As spermatocytes progress through cell division, Aurora B accumulates in the central spindle midzone (Fig. 4 c). In chromosome-containing cells of fsl and suo mutants, Aurora B behavior is identical to wild type (Fig. 4 b and d; unpublished data). In chromosome-free metaphase-like figures from both fsl and suo mutants, Aurora B displays a diffuse staining (unpublished data). However, as these cells move toward telophase, Aurora B accumulates in the central spindle midzone, as occurs in wild type (Fig. 4, e and f). Together, these results clearly show that Aurora B concentration in the central spindle does not require its previous localization at kinetochores. In addition, they strongly suggest that the role played by Aurora B during cytokinesis is independent of that played in chromosome structure and segregation.

Bottom Line: The cells containing chromosome-free spindles are also able to assemble regular cytokinetic structures and cleave normally.In addition, chromosome-free spindles normally accumulate the Aurora B kinase at their midzones.This suggests that the association of Aurora B with chromosomes is not a prerequisite for its accumulation at the central spindle, or for its function during cytokinesis.

View Article: PubMed Central - PubMed

Affiliation: Istituto Pasteur Fondazione Cenci Bolognetti, 00185 Rome, Italy.

ABSTRACT
A large body of work indicates that chromosomes play a key role in the assembly of both a centrosomal and centrosome-containing spindles. In animal systems, the absence of chromosomes either prevents spindle formation or allows the assembly of a metaphase-like spindle that fails to evolve into an ana-telophase spindle. Here, we show that Drosophila secondary spermatocytes can assemble morphologically normal spindles in the absence of chromosomes. The Drosophila mutants fusolo and solofuso are severely defective in chromosome segregation and produce secondary spermatocytes that are devoid of chromosomes. The centrosomes of these anucleated cells form robust asters that give rise to bipolar spindles that undergo the same ana-telophase morphological transformations that characterize normal spindles. The cells containing chromosome-free spindles are also able to assemble regular cytokinetic structures and cleave normally. In addition, chromosome-free spindles normally accumulate the Aurora B kinase at their midzones. This suggests that the association of Aurora B with chromosomes is not a prerequisite for its accumulation at the central spindle, or for its function during cytokinesis.

Show MeSH
Related in: MedlinePlus