Meiosis in Coprinus Lagopus: A Comparative Study with Light and Electron Microscopy

1967 ◽  
Vol 2 (4) ◽  
pp. 529-536
Author(s):  
B. C. LU
Keyword(s):  
Nuclear Fusion ◽  
Light And Electron Microscopy ◽  
Central Component ◽  
Fruiting Bodies ◽  
Homologous Pairing ◽  
Animal Cells ◽  
Characteristic Structure ◽  
Homologous Chromosomes ◽  
Central Spindle ◽  
Spindle Microtubules

Meiosis within fruiting bodies of Coprinus lagopus Fr. is closely synchronized. This conveniently facilitates joint light- and electron-microscope observations. Before nuclear fusion the chromatin appears diffuse in the light microscope; after nuclear fusion individual chromosomes can be recognized. In the electron micrographs the chromatin of pre-fusion and early fusion nuclei cannot be recognized as defined structures with the fixation and staining procedures employed. At the time of synapsis the lateral components of the synaptinemal complexes can be seen in the micrographs. The pairing process of the two chromosomes of the homologous pairs is believed to involve two steps: (1) two homologous chromosomes become aligned in parallel, and (2) pairing occurs by formation of the synaptinemal complex including the central synaptic component. The term synaptic centre is coined for the central component, which is believed to be the zone where crossing-over occurs. The formation of this structure in relation to homologous pairing, and the structural organization of the synaptinemal complexes are discussed. At meiotic metaphase, the chromosomes congregate around the central spindle microtubules. They are contracted and contain densely packed chromatin fibrils. Two types of spindle microtubules are demonstrated: (1) the chromosomal microtubules directly connecting the chromosomes to the centrosomes, and (2) the central spindle microtubules connecting the two centrosomes. The centrosomes are round, fibril-containing bodies approximately 0.3 µ in diameter. They have been observed outside the nuclear envelope at pachytene, but do not show the characteristic structure normally found in animal cells.

Correlative light and electron microscopy: Counting centrioles in individual sea urchin zygotes previously followed in vivo

1993 ◽  
Vol 51 ◽  
pp. 178-179
Author(s):  
Greenfield Sluder ◽  
Frederick J. Miller
Keyword(s):  
Sea Urchin ◽  
Large Population ◽  
Light And Electron Microscopy ◽  
Experimental System ◽  
Animal Cells ◽  
Mitotic Apparatus ◽  
Cell Cycles ◽  
Central Spindle ◽  
Pericentriolar Material

Centrosomes are the ensembles of structures that define the poles of the mitotic apparatus. In animal cells, a centrosome typically consists of a pair of orthogonally arranged centrioles associated with osmiophilic pericentriolar material which nucleates the microtubules of the aster and central spindle. The precise doubling, or reproduction, of the centrosome during interphase is an important event in the cell’s preparations for mitosis.To characterize the mechanisms that control centrosome reproduction we need to follow the behavior of centrosomes within individual cells over several cell cycles. We use sea urchin zygotes as an experimental system because they have a rapid cell cycle, are large enough (100 um diameter) to easily manipulate, and are optically clear. However, the experiments pose two challenges. The first is to follow the behavior of centrosomes within individual zygotes for several hours with the light microscope and then recover just those individuals from a large population for ultrastructural analysis.

scholarly journals CENP-32 is required to maintain centrosomal dominance in bipolar spindle assembly

2015 ◽  
Vol 26 (7) ◽  
pp. 1225-1237 ◽  
Author(s):  
Shinya Ohta ◽  
Laura Wood ◽  
Iyo Toramoto ◽  
Ken-Ichi Yagyu ◽  
Tatsuo Fukagawa ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Additional Data ◽  
Weak Interactions ◽  
Metaphase Plate ◽  
Spindle Pole ◽  
Animal Cells ◽  
Central Spindle ◽  
Spindle Poles ◽  
Spindle Microtubules ◽  
Bipolar Spindles

Centrosomes nucleate spindle formation, direct spindle pole positioning, and are important for proper chromosome segregation during mitosis in most animal cells. We previously reported that centromere protein 32 (CENP-32) is required for centrosome association with spindle poles during metaphase. In this study, we show that CENP-32 depletion seems to release centrosomes from bipolar spindles whose assembly they had previously initiated. Remarkably, the resulting anastral spindles function normally, aligning the chromosomes to a metaphase plate and entering anaphase without detectable interference from the free centrosomes, which appear to behave as free asters in these cells. The free asters, which contain reduced but significant levels of CDK5RAP2, show weak interactions with spindle microtubules but do not seem to make productive attachments to kinetochores. Thus CENP-32 appears to be required for centrosomes to integrate into a fully functional spindle that not only nucleates astral microtubules, but also is able to nucleate and bind to kinetochore and central spindle microtubules. Additional data suggest that NuMA tethers microtubules at the anastral spindle poles and that augmin is required for centrosome detachment after CENP-32 depletion, possibly due to an imbalance of forces within the spindle.

The cellular program for the formation and dissolution of the synaptonemal complex in Coprinus

1984 ◽  
Vol 67 (1) ◽  
pp. 25-43
Author(s):  
B.C. Lu
Keyword(s):  
Protein Synthesis ◽  
Synaptonemal Complex ◽  
Transition Point ◽  
Dense Body ◽  
Coprinus Cinereus ◽  
Central Component ◽  
Homologous Pairing ◽  
Homologous Chromosomes ◽  
Inhibition Of Protein Synthesis ◽  
Meiotic System

Inhibition of protein synthesis by cycloheximide on processes in meiosis was used to probe the cellular program for the formation and dissolution of the synaptonemal complex (SC) in the synchronous meiotic system of Coprinus cinereus. The pathway for the synthesis and assembly of the synaptonemal complex is proposed to be as follows: (1) synthesis and assembly of lateral components on the chromosomes; (2) synthesis and assembly of the central components in the nucleolus; (3) the lateral components of the homologous chromosomes are brought together to pair when the homologous pairing occurs at zygotene; (4) the transport of the central components from the nucleolus to join the paired lateral components and thus complete the synaptonemal complex. Continued protein synthesis is required for all steps. Step (1) is nearly complete 2 h after the onset of karyogamy, because continued assembly is possible in the presence of cycloheximide. The transition point for step (2) is 4 h after the onset of karyogamy, as inhibition at this point results in accumulation of central components in the nucleolar dense body. The paired lateral components of step (3) are deprived of the central component. The transition point for step (4) is 5 h after the onset of karyogamy, for inhibition at this point no longer prevents transport. Two steps are proposed for dissociation and dissolution of the SC at the end of pachytene. Protein synthesis is required for the dissolution of SC. Inhibition at this point causes accumulation of polycomplexes. Mutations in various organisms from the literature relating to the SC support the validity of the proposed pathway.

scholarly journals Paired arrangement of kinetochores together with microtubule pivoting and dynamics drive kinetochore capture in meiosis I

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Gheorghe Cojoc ◽  
Ana-Maria Florescu ◽  
Alexander Krull ◽  
Anna H. Klemm ◽  
Nenad Pavin ◽  
...  
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
General Feature ◽  
Protein Complexes ◽  
Spindle Pole ◽  
Single Object ◽  
Homologous Chromosomes ◽  
Angular Movement ◽  
Spindle Microtubules ◽  
Meiosis I

Abstract Kinetochores are protein complexes on the chromosomes, whose function as linkers between spindle microtubules and chromosomes is crucial for proper cell division. The mechanisms that facilitate kinetochore capture by microtubules are still unclear. In the present study, we combine experiments and theory to explore the mechanisms of kinetochore capture at the onset of meiosis I in fission yeast. We show that kinetochores on homologous chromosomes move together, microtubules are dynamic and pivot around the spindle pole, and the average capture time is 3–4 minutes. Our theory describes paired kinetochores on homologous chromosomes as a single object, as well as angular movement of microtubules and their dynamics. For the experimentally measured parameters, the model reproduces the measured capture kinetics and shows that the paired configuration of kinetochores accelerates capture, whereas microtubule pivoting and dynamics have a smaller contribution. Kinetochore pairing may be a general feature that increases capture efficiency in meiotic cells.

scholarly journals Modulated targeting of GFP-AtMAP65-1 to central spindle microtubules during division

2005 ◽  
Vol 43 (4) ◽  
pp. 469-478 ◽  
Author(s):  
Guojie Mao ◽  
Jordi Chan ◽  
Grant Calder ◽  
John H. Doonan ◽  
Clive W. Lloyd
Keyword(s):  
Central Spindle ◽  
Spindle Microtubules

scholarly journals Drosophila F-BAR protein Syndapin contributes to coupling the plasma membrane and contractile ring in cytokinesis

Open Biology ◽  
2013 ◽  
Vol 3 (8) ◽  
pp. 130081 ◽  
Author(s):  
Tetsuya Takeda ◽  
Iain M. Robinson ◽  
Matthew M. Savoian ◽  
John R. Griffiths ◽  
Anthony D. Whetton ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Curvature ◽  
Cellular Process ◽  
Cleavage Furrow ◽  
Contractile Ring ◽  
Functional Interaction ◽  
Cortical Dynamics ◽  
Central Spindle ◽  
Bar Domain ◽  
Spindle Microtubules

Cytokinesis is a highly ordered cellular process driven by interactions between central spindle microtubules and the actomyosin contractile ring linked to the dynamic remodelling of the plasma membrane. The mechanisms responsible for reorganizing the plasma membrane at the cell equator and its coupling to the contractile ring in cytokinesis are poorly understood. We report here that Syndapin, a protein containing an F-BAR domain required for membrane curvature, contributes to the remodelling of the plasma membrane around the contractile ring for cytokinesis. Syndapin colocalizes with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P 2 ) at the cleavage furrow, where it directly interacts with a contractile ring component, Anillin. Accordingly, Anillin is mislocalized during cytokinesis in Syndapin mutants. Elevated or diminished expression of Syndapin leads to cytokinesis defects with abnormal cortical dynamics. The minimal segment of Syndapin, which is able to localize to the cleavage furrow and induce cytokinesis defects, is the F-BAR domain and its immediate C-terminal sequences. Phosphorylation of this region prevents this functional interaction, resulting in reduced ability of Syndapin to bind to and deform membranes. Thus, the dephosphorylated form of Syndapin mediates both remodelling of the plasma membrane and its proper coupling to the cytokinetic machinery.

Regulation of Mitosis

1969 ◽  
Vol 5 (3) ◽  
pp. 745-755
Author(s):  
W. T. JACKSON
Keyword(s):  
Mitotic Spindle ◽  
Time Lapse ◽  
Polarization Microscopy ◽  
Animal Cells ◽  
Higher Plant ◽  
Competitive Antagonism ◽  
Dividing Cells ◽  
Spindle Microtubules ◽  
Giant Nuclei

Earlier studies on the effects of the herbicide isopropyl N-phenylcarbamate (IPC) on mitosis revealed blocked metaphases, multinucleate cells, giant nuclei and an increase in number of partly contracted chromosomes. It was assumed that IPC, like colchicine, was causing these effects by disruption of the spindle apparatus by destroying the spindle microtubules. The animal hormone melatonin causes an increase in birefringence of the mitotic spindle in animal cells, presumably by increasing the number of microtubules. We have studied the effects of IPC, melatonin, and combinations of the two on mitosis in dividing endosperm cells of the African blood lily (Haemanthus katherinae Baker) in vivo by phase-contrast and polarization microscopy. Both qualitative and quantitative data are presented. Interpretation of these results has been aided materially by a time-lapse cinemicrographic analysis of dividing cells subjected to 1 and 10 p.p.m. IPC (unpublished) and by an accompanying fine-structural analysis of untreated and IPC-treated cells. Mitosis was disrupted by 0.01-10 p.p.m. IPC, the severity of the effect depending on both concentration and stage of mitosis of the cell at the time of treatment. Concentrations of IPC that caused cessation of chromosome movement also caused loss of birefringence of the mitotic spindle. Melatonin increased birefringence of the mitotic spindle in these plant cells and partly nullified the adverse effects of IPC. The results of this study demonstrate that the herbicide IPC, under our conditions, causes disruption of mitosis and loss of birefringence of the spindle. And it has been established that an animal hormone is capable of increasing the birefringence, and presumably the number of microtubules, of the mitotic spindle in dividing endosperm cells of a higher plant. Although melatonin is capable of partly nullifying the effects of IPC, a competitive antagonism is not postulated.

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.

The assembly of the synaptinemal complex

1977 ◽  
Vol 277 (955) ◽  
pp. 235-243 ◽  
Keyword(s):  
Central Region ◽  
Three Dimensional ◽  
Chiasma Formation ◽  
Central Component ◽  
Lateral Component ◽  
Late Zygotene ◽  
Homologous Chromosomes ◽  
Synaptinemal Complex ◽  
Central Regions ◽  
Dimensional Reconstruction

The assembly of the synaptinemal complex in the ascomycete Neottiella was studied by three-dimensional reconstruction of a late zygotene nucleus. A single banded lateral component is formed between the two sister chromatids of each homologous chromosome prior to their pairing. The central regions are pre-assembled in organized form in folds of the granular part of the nucleolus and then converted into an amorphous transport form. The latter appears to move through the nucleoplasm to sites between the lateral components of synapsing homologous chromosomes. The central region material is reorganized into blocks with a recognizable central component and attached to one lateral component. The last step in the completion of the synaptinemal complex is the association of the free surface of the organized central region with the corresponding segment of the homologous lateral component. The findings are discussed in relation to mechanisms of chromosome pairing and chiasma formation.

scholarly journals The Mammalian Septin MSF Localizes with Microtubules and Is Required for Completion of Cytokinesis

2002 ◽  
Vol 13 (10) ◽  
pp. 3532-3545 ◽  
Author(s):  
Mark C. Surka ◽  
Christopher W. Tsang ◽  
William S. Trimble
Keyword(s):  
Cell Death ◽  
Cell Division ◽  
Nuclear Division ◽  
Cleavage Furrow ◽  
Small Interfering Rnas ◽  
Animal Cells ◽  
Central Spindle ◽  
Synchronized Cells ◽  
Binucleated Cells ◽  
And Function

Cytokinesis in animal cells involves the contraction of an actomyosin ring formed at the cleavage furrow. Nuclear division, or karyokinesis, must be precisely timed to occur before cytokinesis in order to prevent genetic anomalies that would result in either cell death or uncontrolled cell division. The septin family of GTPase proteins has been shown to be important for cytokinesis although little is known about their role during this process. Here we investigate the distribution and function of the mammalian septin MSF. We show that during interphase, MSF colocalizes with actin, microtubules, and another mammalian septin, Nedd5, and coprecipitates with six septin proteins. In addition, transfections of various MSF isoforms reveal that MSF-A specifically localizes with microtubules and that this localization is disrupted by nocodazole treatment. Furthermore, MSF isoforms localize primarily with tubulin at the central spindle during mitosis, whereas Nedd5 is mainly associated with actin. Microinjection of affinity-purified anti-MSF antibodies into synchronized cells, or depletion of MSF by small interfering RNAs, results in the accumulation of binucleated cells and in cells that have arrested during cytokinesis. These results reveal that MSF is required for the completion of cytokinesis and suggest a role that is distinct from that of Nedd5.

Sign in / Sign up

Export Citation Format

Share Document