Limits...
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.

Show MeSH

Related in: MedlinePlus

First meiotic division in fsl mutant males. Cells were stained for tubulin (green), centrin (orange), and DNA (blue). (a and b) Meiotic division in wild-type males. (a) Metaphase I; (b) Late telophase I; (c–e) Meiotic division in fsl males. (c) Metaphase I; (d) Late telophase I with nonsegregating chromosomes at the center of the cell; (e) Late telophase I with all chromosomes segregating to only one of the two presumptive daughter cells. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172764&req=5

fig1: First meiotic division in fsl mutant males. Cells were stained for tubulin (green), centrin (orange), and DNA (blue). (a and b) Meiotic division in wild-type males. (a) Metaphase I; (b) Late telophase I; (c–e) Meiotic division in fsl males. (c) Metaphase I; (d) Late telophase I with nonsegregating chromosomes at the center of the cell; (e) Late telophase I with all chromosomes segregating to only one of the two presumptive daughter cells. Bar, 10 μm.

Mentions: To characterize the meiotic phenotype of fsl and suo, we made larval and adult testis preparations that were simultaneously stained for tubulin, centrin, and DNA. The anti–human centrin (HsCen1p) antibody (Paoletti et al., 1996) decorates Drosophila centrioles (Riparbelli et al., 2002), facilitating distinction between first and second meiotic divisions, which display two and one centriole at each pole, respectively. The analysis of fsl1/Df, fsl1/fsl1, fsl2/Df, and fsl2/fsl2 testes showed that these mutant combinations do not substantially differ in terms of severity of the phenotype, displaying a common defect in chromosome segregation. Thus, we focused on fsl1/fsl1 and fsl1/Df for detailed characterization of the meiotic phenotype. In fsl1/fsl1 and fsl1/Df, meiotic prometaphase and metaphase I figures are normal (Fig. 1 c). However, in most ana-telophases, chromosome segregation is disrupted (Fig. 1, d and e; Table I). In approximately half of mutant ana-telophase I cells, all chromosomes segregate to one pole only (Fig. 1 e and Table I), leading to the formation of secondary spermatocytes that are completely devoid of chromosomes (Fig. 2). Chromosome-containing fsl secondary spermatocytes form a regular spindle and exhibit the same aberrant chromosome behavior seen in the first meiotic division (unpublished data; see Fig. 5 a). In fsl secondary spermatocytes without chromosomes, centrosomes nucleate robust astral arrays of MTs that move to the opposite cell poles (Fig. 2 a′). These asters give rise to metaphase-like spindles devoid of chromosomes that differ from their wild-type counterparts only for the absence of kinetochore fibers (Fig. 2, a and a′). It should be noted that in these chromosome-free spindles, there is limited overlapping between the antiparallel MTs emanating from the opposite poles (Fig. 2 a′). However, little or no overlapping of these MTs is also seen in wild-type metaphase spindles (Fig. 2 a; Cenci et al., 1994). Chromosome-free spindles evolve into an anaphase A-like configuration, which again displays little or no MT overlapping at the center of the cell, as occurs in wild-type anaphases (Fig. 2, b and b′; Cenci et al., 1994). These anaphase A-like spindles undergo anaphase B (Fig. 2, c and c′), assemble a morphologically normal central spindle, and elongate to form telophase figures that are indistinguishable from their wild-type counterparts (Fig. 2, d–e′). It should be noted that in fsl mutants, the frequency of chromosome-free metaphase/early anaphase II figures and the frequency of chromosome-free telophase II figures are comparable (Table I). This indicates that most (if not all) metaphase-like spindles without chromosomes have the ability to form a central spindle and to proceed to telophase.


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)

First meiotic division in fsl mutant males. Cells were stained for tubulin (green), centrin (orange), and DNA (blue). (a and b) Meiotic division in wild-type males. (a) Metaphase I; (b) Late telophase I; (c–e) Meiotic division in fsl males. (c) Metaphase I; (d) Late telophase I with nonsegregating chromosomes at the center of the cell; (e) Late telophase I with all chromosomes segregating to only one of the two presumptive daughter cells. Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172764&req=5

fig1: First meiotic division in fsl mutant males. Cells were stained for tubulin (green), centrin (orange), and DNA (blue). (a and b) Meiotic division in wild-type males. (a) Metaphase I; (b) Late telophase I; (c–e) Meiotic division in fsl males. (c) Metaphase I; (d) Late telophase I with nonsegregating chromosomes at the center of the cell; (e) Late telophase I with all chromosomes segregating to only one of the two presumptive daughter cells. Bar, 10 μm.
Mentions: To characterize the meiotic phenotype of fsl and suo, we made larval and adult testis preparations that were simultaneously stained for tubulin, centrin, and DNA. The anti–human centrin (HsCen1p) antibody (Paoletti et al., 1996) decorates Drosophila centrioles (Riparbelli et al., 2002), facilitating distinction between first and second meiotic divisions, which display two and one centriole at each pole, respectively. The analysis of fsl1/Df, fsl1/fsl1, fsl2/Df, and fsl2/fsl2 testes showed that these mutant combinations do not substantially differ in terms of severity of the phenotype, displaying a common defect in chromosome segregation. Thus, we focused on fsl1/fsl1 and fsl1/Df for detailed characterization of the meiotic phenotype. In fsl1/fsl1 and fsl1/Df, meiotic prometaphase and metaphase I figures are normal (Fig. 1 c). However, in most ana-telophases, chromosome segregation is disrupted (Fig. 1, d and e; Table I). In approximately half of mutant ana-telophase I cells, all chromosomes segregate to one pole only (Fig. 1 e and Table I), leading to the formation of secondary spermatocytes that are completely devoid of chromosomes (Fig. 2). Chromosome-containing fsl secondary spermatocytes form a regular spindle and exhibit the same aberrant chromosome behavior seen in the first meiotic division (unpublished data; see Fig. 5 a). In fsl secondary spermatocytes without chromosomes, centrosomes nucleate robust astral arrays of MTs that move to the opposite cell poles (Fig. 2 a′). These asters give rise to metaphase-like spindles devoid of chromosomes that differ from their wild-type counterparts only for the absence of kinetochore fibers (Fig. 2, a and a′). It should be noted that in these chromosome-free spindles, there is limited overlapping between the antiparallel MTs emanating from the opposite poles (Fig. 2 a′). However, little or no overlapping of these MTs is also seen in wild-type metaphase spindles (Fig. 2 a; Cenci et al., 1994). Chromosome-free spindles evolve into an anaphase A-like configuration, which again displays little or no MT overlapping at the center of the cell, as occurs in wild-type anaphases (Fig. 2, b and b′; Cenci et al., 1994). These anaphase A-like spindles undergo anaphase B (Fig. 2, c and c′), assemble a morphologically normal central spindle, and elongate to form telophase figures that are indistinguishable from their wild-type counterparts (Fig. 2, d–e′). It should be noted that in fsl mutants, the frequency of chromosome-free metaphase/early anaphase II figures and the frequency of chromosome-free telophase II figures are comparable (Table I). This indicates that most (if not all) metaphase-like spindles without chromosomes have the ability to form a central spindle and to proceed to telophase.

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