scholarly journals Spindle Self-organization and Cytokinesis During Male Meiosis in asterless Mutants of Drosophila melanogaster

1998 ◽  
Vol 142 (3) ◽  
pp. 751-761 ◽  
Author(s):  
Silvia Bonaccorsi ◽  
Maria Grazia Giansanti ◽  
Maurizio Gatti
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosome Segregation ◽  
Spindle Assembly ◽  
Male Meiosis ◽  
Self Organization ◽  
Wild Type ◽  
Female Meiosis ◽  
Classical View ◽  
Central Spindle ◽  
Spindle Microtubules

While Drosophila female meiosis is anastral, both meiotic divisions in Drosophila males exhibit prominent asters. We have identified a gene we call asterless (asl) that is required for aster formation during male meiosis. Ultrastructural analysis showed that asl mutants have morphologically normal centrioles. However, immunostaining with antibodies directed either to γ tubulin or centrosomin revealed that these proteins do not accumulate in the centrosomes, as occurs in wild-type. Thus, asl appears to specify a function required for the assembly of centrosomal material around the centrioles. Despite the absence of asters, meiotic cells of asl mutants manage to develop an anastral spindle. Microtubules grow from multiple sites around the chromosomes, and then focus into a peculiar bipolar spindle that mediates chromosome segregation, although in a highly irregular way. Surprisingly, asl spermatocytes eventually form a morphologically normal ana–telophase central spindle that has full ability to stimulate cytokinesis. These findings challenge the classical view on central spindle assembly, arguing for a self-organization of this structure from either preexisting or newly formed microtubules. In addition, these findings strongly suggest that the asters are not required for signaling cytokinesis.

Evidence that the spindle assembly checkpoint does not regulate APCFzy activity in Drosophila female meiosis

Genome ◽  
2012 ◽  
Vol 55 (1) ◽  
pp. 63-67 ◽  
Author(s):  
Osamah Batiha ◽  
Andrew Swan
Keyword(s):  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Cyclin B ◽  
Meiotic Spindle ◽  
Loss Of Function ◽  
Female Meiosis ◽  
Chromosome Attachment ◽  
Spindle Microtubules ◽  
Made In

The spindle assembly checkpoint (SAC) plays an important role in mitotic cells to sense improper chromosome attachment to spindle microtubules and to inhibit APCFzy-dependent destruction of cyclin B and Securin; consequent initiation of anaphase until correct attachments are made. In Drosophila , SAC genes have been found to play a role in ensuring proper chromosome segregation in meiosis, possibly reflecting a similar role for the SAC in APCFzy inhibition during meiosis. We found that loss of function mutations in SAC genes, Mad2, zwilch, and mps1, do not lead to the predicted rise in APCFzy-dependent degradation of cyclin B either globally throughout the egg or locally on the meiotic spindle. Further, the SAC is not responsible for the inability of APCFzy to target cyclin B and promote anaphase in metaphase II arrested eggs from cort mutant females. Our findings support the argument that SAC proteins play checkpoint independent roles in Drosophila female meiosis and that other mechanisms must function to control APC activity.

A requirement for the Abnormal Spindle protein to organise microtubules of the central spindle for cytokinesis inDrosophila

2002 ◽  
Vol 115 (5) ◽  
pp. 913-922 ◽  
Author(s):  
Maria Giovanna Riparbelli ◽  
Giuliano Callaini ◽  
David M. Glover ◽  
Maria do Carmo Avides
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Male Meiosis ◽  
Wild Type ◽  
Female Meiosis ◽  
Central Spindle ◽  
Spindle Poles ◽  
Late Anaphase ◽  
Mutant Cells ◽  
Sperm Aster

Drosophila abnormal spindle (asp) mutants exhibit a mitotic metaphase checkpoint arrest with abnormal spindle poles, which reflects a requirement for Asp for the integrity of microtubule organising centres (MTOCs). In male meiosis, the absence of a strong spindle integrity checkpoint enables asp mutant cells to proceed through anaphase and telophase. However, the central spindle region is not correctly organised and cells frequently fail to complete cytokinesis. This contrasts with meiosis in wild-type males where at late anaphase a dense array of microtubules forms in the central spindle region that has Asp localised at its border. We speculate that Asp is associated with the minus ends of microtubules that have been released from the spindle poles to form the central spindle. A parallel situation arises in female meiosis where Asp not only associates with the minus ends of microtubules at the acentriolar poles but also with the central spindle pole body that forms between the two tandem spindles of meiosis II. Upon fertilisation, Asp is also recruited to the MTOC that nucleates the sperm aster. Asp is required for growth of the microtubules of the sperm aster,which in asp mutants remains diminutive and so prevents migration of the pronuclei.

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

2003 ◽  
Vol 160 (7) ◽  
pp. 993-999 ◽  
Author(s):  
Elisabetta Bucciarelli ◽  
Maria Grazia Giansanti ◽  
Silvia Bonaccorsi ◽  
Maurizio Gatti
Keyword(s):  
Chromosome Segregation ◽  
Spindle Assembly ◽  
Male Meiosis ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Spindle Formation ◽  
Central Spindle ◽  
Morphological Transformations ◽  
Bipolar Spindles ◽  
Drosophila Mutants

Alarge body of work indicates that chromosomes play a key role in the assembly of both acentrosomal 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.

scholarly journals Insights from the reconstitution of the divergent outer kinetochore of Drosophila melanogaster

Open Biology ◽  
2016 ◽  
Vol 6 (2) ◽  
pp. 150236 ◽  
Author(s):  
Yahui Liu ◽  
Arsen Petrovic ◽  
Pascaline Rombaut ◽  
Shyamal Mosalaganti ◽  
Jenny Keller ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosome Segregation ◽  
Functional Organization ◽  
Histone H3 Variant ◽  
Centromeric Protein ◽  
Spindle Microtubules ◽  
Specialized Region ◽  
Structural Methods ◽  
Mitosis And Meiosis ◽  
Shed Light

Accurate chromosome segregation during mitosis and meiosis is crucial for cellular and organismal viability. Kinetochores connect chromosomes with spindle microtubules and are essential for chromosome segregation. These large protein scaffolds emerge from the centromere, a specialized region of the chromosome enriched with the histone H3 variant CENP-A. In most eukaryotes, the kinetochore core consists of the centromere-proximal constitutive centromere-associated network (CCAN), which binds CENP-A and contains 16 subunits, and of the centromere-distal Knl1 complex, Mis12 complex, Ndc80 complex (KMN) network, which binds microtubules and contains 10 subunits. In the fruitfly, Drosophila melanogaster, the kinetochore underwent remarkable simplifications. All CCAN subunits, with the exception of centromeric protein C (CENP-C), and two KMN subunits, Dsn1 and Zwint, cannot be identified in this organism. In addition, two paralogues of the KMN subunit Nnf1 (Nnf1a and Nnf1b) are present. Finally, the Spc105R subunit, homologous to human Knl1/CASC5, underwent considerable sequence changes in comparison with other organisms. We combined biochemical reconstitution with biophysical and structural methods to investigate how these changes reflect on the organization of the Drosophila KMN network. We demonstrate that the Nnf1a and Nnf1b paralogues are subunits of distinct complexes, both of which interact directly with Spc105R and with CENP-C, for the latter of which we identify a binding site on the Mis12 subunit. Our studies shed light on the structural and functional organization of a highly divergent kinetochore particle.

scholarly journals Central-spindle microtubules are strongly coupled to chromosomes during both anaphase A and anaphase B

2019 ◽  
Vol 30 (19) ◽  
pp. 2503-2514 ◽  
Author(s):  
Che-Hang Yu ◽  
Stefanie Redemann ◽  
Hai-Yin Wu ◽  
Robert Kiewisz ◽  
Tae Yeon Yoo ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Tomographic Reconstruction ◽  
Mitotic Spindles ◽  
Strongly Coupled ◽  
Central Spindle ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Spindle Microtubules ◽  
Anaphase B ◽  
Chromosome Motion

Spindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and spindle ultrastructure can provide insight into the behaviors of microtubules, helping elucidate the mechanism of chromosome segregation. Much work has focused on the dynamics and organization of kinetochore microtubules, that is, on the region between chromosomes and poles. In comparison, microtubules in the central-spindle region, between segregating chromosomes, have been less thoroughly characterized. Here, we report measurements of the movement of central-spindle microtubules during chromosome segregation in human mitotic spindles and Caenorhabditis elegans mitotic and female meiotic spindles. We found that these central-spindle microtubules slide apart at the same speed as chromosomes, even as chromosomes move toward spindle poles. In these systems, damaging central-spindle microtubules by laser ablation caused an immediate and complete cessation of chromosome motion, suggesting a strong coupling between central-spindle microtubules and chromosomes. Electron tomographic reconstruction revealed that the analyzed anaphase spindles all contain microtubules with both ends between segregating chromosomes. Our results provide new dynamical, functional, and ultrastructural characterizations of central-spindle microtubules during chromosome segregation in diverse spindles and suggest that central-spindle microtubules and chromosomes are strongly coupled in anaphase.

scholarly journals The human Mis12 complex is required for kinetochore assembly and proper chromosome segregation

2006 ◽  
Vol 173 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Susan L. Kline ◽  
Iain M. Cheeseman ◽  
Tetsuya Hori ◽  
Tatsuo Fukagawa ◽  
Arshad Desai
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Essential Role ◽  
Stable Complex ◽  
Wild Type ◽  
Outer Plate ◽  
Checkpoint Protein ◽  
Kinetochore Assembly ◽  
Attachment Sites ◽  
Spindle Microtubules

During cell division, kinetochores form the primary chromosomal attachment sites for spindle microtubules. We previously identified a network of 10 interacting kinetochore proteins conserved between Caenorhabditis elegans and humans. In this study, we investigate three proteins in the human network (hDsn1Q9H410, hNnf1PMF1, and hNsl1DC31). Using coexpression in bacteria and fractionation of mitotic extracts, we demonstrate that these proteins form a stable complex with the conserved kinetochore component hMis12. Human or chicken cells depleted of Mis12 complex subunits are delayed in mitosis with misaligned chromosomes and defects in chromosome biorientation. Aligned chromosomes exhibited reduced centromere stretch and diminished kinetochore microtubule bundles. Consistent with this, localization of the outer plate constituent Ndc80HEC1 was severely reduced. The checkpoint protein BubR1, the fibrous corona component centromere protein (CENP) E, and the inner kinetochore proteins CENP-A and CENP-H also failed to accumulate to wild-type levels in depleted cells. These results indicate that a four-subunit Mis12 complex plays an essential role in chromosome segregation in vertebrates and contributes to mitotic kinetochore assembly.

scholarly journals The Drosophila Kinesin-like Protein KLP67A Is Essential for Mitotic and Male Meiotic Spindle Assembly

2004 ◽  
Vol 15 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Rita Gandhi ◽  
Silvia Bonaccorsi ◽  
Diana Wentworth ◽  
Stephen Doxsey ◽  
Maurizio Gatti ◽  
...  
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Mutational Analysis ◽  
Spindle Assembly ◽  
Male Meiosis ◽  
Meiotic Spindle ◽  
Drosophila Cell ◽  
Centrosome Separation ◽  
Mutant Cells

We have performed a mutational analysis together with RNA interference to determine the role of the kinesin-like protein KLP67A in Drosophila cell division. During both mitosis and male meiosis, Klp67A mutations cause an increase in MT length and disrupt discrete aspects of spindle assembly, as well as cytokinesis. Mutant cells exhibit greatly enlarged metaphase spindle as a result of excessive MT polymerization. The analysis of both living and fixed cells also shows perturbations in centrosome separation, chromosome segregation, and central spindle assembly. These data demonstrate that the MT plus end-directed motor KLP67A is essential for spindle assembly during mitosis and male meiosis and suggest that the regulation of MT plus-end polymerization is a key determinant of spindle architecture throughout cell division.

scholarly journals Central spindle microtubules are strongly coupled to chromosomes during both anaphase A and anaphase B

2019 ◽  
Author(s):  
Che-Hang Yu ◽  
Stefanie Redemann ◽  
Hai-Yin Wu ◽  
Robert Kiewisz ◽  
Tae Yeon Yoo ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Tomographic Reconstruction ◽  
Mitotic Spindles ◽  
Strongly Coupled ◽  
Central Spindle ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Spindle Microtubules ◽  
Anaphase B ◽  
Chromosome Motion

AbstractSpindle microtubules, whose dynamics vary over time and at different locations, cooperatively drive chromosome segregation. Measurements of microtubule dynamics and spindle ultrastructure can provide insight into the behaviors of microtubules, helping elucidate the mechanism of chromosome segregation. Much work has focused on the dynamics and organization of kinetochore microtubules, i.e. on the region between chromosomes and poles. In comparison, microtubules in the central spindle region, between segregating chromosomes, have been less thoroughly characterized. Here, we report measurements of the movement of central spindle microtubules during chromosome segregation in human mitotic spindles, and Caenorhabditis elegans mitotic and female meiotic spindles. We found that these central spindle microtubules slide apart at the same speed as chromosomes, even as chromosomes move towards spindle poles. In these systems, damaging central spindle microtubules by laser ablation caused an immediate and complete cessation of chromosome motion, suggesting a strong coupling between central spindle microtubules and chromosomes. Electron tomographic reconstruction revealed that the analyzed anaphase spindles all contain microtubules with both ends between segregating chromosomes. Our results provide new dynamical, functional, and ultrastructural characterizations of central spindle microtubules during chromosome segregation in diverse spindles, and suggest that central spindle microtubules and chromosomes are strongly coupled in anaphase.

scholarly journals Intrakinetochore stretch is associated with changes in kinetochore phosphorylation and spindle assembly checkpoint activity

2009 ◽  
Vol 184 (3) ◽  
pp. 373-381 ◽  
Author(s):  
Thomas J. Maresca ◽  
Edward D. Salmon
Keyword(s):  
Drosophila Melanogaster ◽  
Green Fluorescent Protein ◽  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Spindle Assembly Checkpoint ◽  
Fluorescent Protein ◽  
Spindle Assembly ◽  
Centromeric Chromatin ◽  
Cell Assays ◽  
Green Fluorescent

Cells have evolved a signaling pathway called the spindle assembly checkpoint (SAC) to increase the fidelity of chromosome segregation by generating a “wait anaphase” signal until all chromosomes are properly aligned within the mitotic spindle. It has been proposed that tension generated by the stretch of the centromeric chromatin of bioriented chromosomes stabilizes kinetochore microtubule attachments and turns off SAC activity. Although biorientation clearly causes stretching of the centromeric chromatin, it is unclear whether the kinetochore is also stretched. To test whether intrakinetochore stretch occurs and is involved in SAC regulation, we developed a Drosophila melanogaster S2 cell line expressing centromere identifier–mCherry and Ndc80–green fluorescent protein to mark the inner and outer kinetochore domains, respectively. We observed stretching within kinetochores of bioriented chromosomes by monitoring both inter- and intrakinetochore distances in live cell assays. This intrakinetochore stretch is largely independent of a 30-fold variation in centromere stretch. Furthermore, loss of intrakinetochore stretch is associated with enhancement of 3F3/2 phosphorylation and SAC activation.

Sign in / Sign up

Export Citation Format

Share Document