Presence of a centromeric filament during meiosis

Genome ◽  
1991 ◽  
Vol 34 (6) ◽  
pp. 888-894 ◽  
Author(s):  
Alberto J. Solari ◽  
Carlos J. Tandler
Keyword(s):  
Synaptonemal Complex ◽  
Staining Technique ◽  
Meiotic Metaphase ◽  
Mitotic Chromosomes ◽  
Intense Staining ◽  
Lateral Element ◽  
Centromeric Chromatin ◽  
Sister Chromatids ◽  
Silver Staining Technique ◽  
Metaphase I

Spermatocytes at meiotic metaphase I and anaphase I have a characteristic centromeric filament in a variety of vertebrate organisms. This centromeric filament was first demonstrated on mouse spermatocytes and its presence is now extended to spermatocytes from the human, rat, golden hamster, bull, and chicken. The visualization of this filament was possible through the use of a novel silver-staining technique, which allows a high contrast between the filament and the centromeric chromatin. In the species cited, the centromeric filament shares an intense staining, a short (0.2–0.6 μm) length, a curved and branched shape, and location inside the centromeric chromatin of seemingly every homologue of the complement. The similarity of staining reactivity and the observation of transitional structures during first meiotic prophase strongly suggest that the centromeric filament is a remnant of a lateral element of the synaptonemal complex, which stays specifically at both centromeric regions of each bivalent. This filament is not found at the second meiotic division or at the centromeres of mitotic chromosomes. It is assumed that this centromeric filament joins the two sister chromatids of each homologue at the centromere and thus ensures the proper coorientation of sister kinetochores at metaphase I. Further testable assumptions on the functions of this filament are presented.Key words: synaptonemal complex, meiosis, meiotic centromeres.

scholarly journals Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1β and SMC3

2003 ◽  
Vol 160 (5) ◽  
pp. 657-670 ◽  
Author(s):  
Maureen Eijpe ◽  
Hildo Offenberg ◽  
Rolf Jessberger ◽  
Ekaterina Revenkova ◽  
Christa Heyting
Keyword(s):  
Synaptonemal Complex ◽  
Sister Chromatid ◽  
Meiotic Prophase ◽  
S Phase ◽  
Synaptonemal Complexes ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Axial Element ◽  
Striking Contrast ◽  
Metaphase I

In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shortly before premeiotic S phase in the nucleus and formed AE-like structures (REC8-AEs) from premeiotic S phase on. Subsequently, meiotic cohesin SMC1β, cohesin SMC3, and AE proteins SCP2 and SCP3 formed dots along REC8-AEs, which extended and fused until they lined REC8-AEs along their length. In metaphase I, SMC1β, SMC3, SCP2, and SCP3 disappeared from the chromosome arms and accumulated around the centromeres, where they stayed until anaphase II. In striking contrast, REC8 persisted along the chromosome arms until anaphase I and near the centromeres until anaphase II. We propose that REC8 provides a basis for AE formation and that the first steps in AE assembly do not require SMC1β, SMC3, SCP2, and SCP3. Furthermore, SMC1β, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I. We propose that REC8 then provides cohesion. RAD51 and/or DMC1 coimmunoprecipitates with REC8, suggesting that REC8 may also provide a basis for assembly of recombination complexes.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. IV. Synaptonemal complex formation in autotetraploids

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 309-318 ◽  
Author(s):  
C. B. Gillies ◽  
J. Kuspira ◽  
R. N. Bhambhani
Keyword(s):  
Synaptonemal Complex ◽  
Theoretical Models ◽  
Triticum Monococcum ◽  
Pachytene Nucleus ◽  
Lateral Element ◽  
A Genome ◽  
Cytogenetic Analyses ◽  
The Difference ◽  
Quadrivalent Frequency ◽  
Metaphase I

Electron microscopy of synaptonemal complex spreads from autotetraploid Triticum monococcum (2n = 4x = 28) revealed a minimum mean of 3.59 multivalents per zygotene–pachytene nucleus. The range of values was from 1 to 6 multivalents per nucleus. Most of the multivalents were quadrivalents with single, medially located pairing partner switch points. Lateral element pairing switches, particularly the few multiple switches, were often accompanied by extensive asynapsis around the switch point. The synaptonemal complex multivalent frequency is considerably higher than the metaphase I quadrivalent frequency previously reported for the same material. Calculations of expected pachytene quadrivalent frequency from metaphase I data, using several published theoretical models, gave values that did not agree with the results obtained here. The difference between the multivalent frequencies at pachytene and metaphase I does not appear to be the result of a correction process. Instead, it could be caused by a combination of preferential pairing or crossing-over and the effects of the position of partner switches and asynapsis associated with switches. Key words: autotetraploid, multivalents, synaptonemal complex, pairing effects.

Indiscriminate synapsis in achiasmate Allium fistulosum L. (Liliaceae)

1992 ◽  
Vol 103 (2) ◽  
pp. 415-422
Author(s):  
G. Jenkins ◽  
A. Okumus
Keyword(s):  
Synaptonemal Complex ◽  
Allium Fistulosum ◽  
Cell Nuclei ◽  
Male Sterile ◽  
Allium Species ◽  
Lateral Element ◽  
Synaptonemal Complexes ◽  
Independent Process ◽  
Surface Spread ◽  
Metaphase I

Seedlings of Allium fistulosum (2n=2x=16) were treated with aqueous colchicine with the intention of inducing tetraploidy. One treated, but undoubled, diploid mutant is described which consistently fails to form any chiasmata at diakinesis and metaphase I of meiosis. Electron microscopy of whole-mount surface-spread synaptonemal complex complements of pollen mother cell nuclei revealed that the achiasmate condition is probably due not only to the failure to complete synapsis, but also to the indiscriminate way in which the chromosomes form synaptonemal complexes during meiotic prophase. Synapsis begins and progresses with complete disregard to homology, with frequent exchanges of pairing partners resulting in the formation of multiple associations comprising heterologous chromosomes. Intrachromosomal synapsis is also evident as fold-back loops. Up to 78% of lateral element length is incorporated into synaptonemal complex, the morphology of which is not unlike that of normal A. fistulosum and other Allium species described previously. However, all the synaptonemal complexes are ineffective in terms of supporting chiasmata, since 16 univalents enter metaphase I and disjoin irregularly at anaphase I. The mutant is as a consequence completely male sterile. The synaptic behaviour observed confirms that the recognition of homology is an independent process and not a prerequisite for synaptonemal complex formation. It is hoped this mutant will be a valuable tool for probing the molecular basis of homology.

scholarly journals Meiotic shugoshins differ from mitotic ones by arginine-reach C-terminal motif in yeast, plant, animals, and human

2016 ◽  
Author(s):  
Tatiana M Grishaeva ◽  
Darya Kulichenko ◽  
Yuri F Bogdanov
Keyword(s):  
Amino Acid ◽  
Structural Difference ◽  
Protein Molecule ◽  
Meiotic Metaphase ◽  
Chromosome Behavior ◽  
Sister Chromatids ◽  
Arginine Residues ◽  
The Difference ◽  
Mitosis And Meiosis ◽  
Metaphase I

Background. Shugoshins (SGOs) are proteins that protect cohesins located at the centromeres of sister chromatids from their early cleavage during mitosis and meiosis in plants, fungi, and animals. Their function is to prevent premature sister-chromatid disjunction and segregation. Meiotic SGOs prevent segregation of sister chromatids in meiosis I, thus permitting homologous chromosomes to segregate and reduce chromosome number to haploid set. The study focused on the structural differences among shugoshins acting during mitosis and meiosis that cause differences in chromosome behavior in these two types of cell division in different organisms. Methods. A bioinformatics analysis of protein domains, conserved amino acid motifs, and physicochemical properties of 32 proteins from 25 species of plants, fungi, and animals was performed. Results. We identified a C-terminal arginine-reach amino acid motif that is highly evolutionarily conserved among the shugoshins protecting centromere cohesion of sister chromatids in meiotic anaphase I, but not among mitotic shugoshins. The motif looks like “arginine comb” capable of interaction by hydrogen bonds with guanine bases in the small groove of DNA helix. Shugoshins in different eukaryotic kingdoms differ also in the sets and location of amino acid motifs and the number of α-helical regions in the protein molecule. Discussion. Meiosis-specific arginine-reach motif may be responsible for formation of SGO-DNA nucleoprotein complex, thus protecting meiotic shugoshins from degradation during meiotic metaphase I and anaphase I, while mitotic SGOs have a motif with less number of arginine residues. This structural difference between meiotic and mitotic shugoshins, probably, could be a key molecular element of the prolonged shugoshin resistance to degradation during meiotic metaphase I and anaphase I and be one of the molecular elements causing the difference in chromosome behavior in meiosis and mitosis. The finding of differences in SGO structure in plant, fungi and animals supports idea of independent evolution of meiosis in different lineages of multicellular organisms.

Phosphorylation of histone H3 is correlated with changes in the maintenance of sister chromatid cohesion during meiosis in maize, rather than the condensation of the chromatin

2000 ◽  
Vol 113 (18) ◽  
pp. 3217-3226 ◽  
Author(s):  
E. Kaszas ◽  
W.Z. Cande
Keyword(s):  
Sister Chromatid ◽  
Meiotic Chromosome ◽  
Histone H3 ◽  
Sister Chromatid Cohesion ◽  
Chromosome Condensation ◽  
Mitotic Chromosomes ◽  
Sister Chromatids ◽  
H3 Phosphorylation ◽  
Chromatid Cohesion ◽  
Metaphase I

Meiotic chromosome condensation is a unique process, characterized by dramatic changes in chromosome morphology that are required for the correct progression of pairing, synapsis, recombination and segregation of sister chromatids. We used an antibody that recognizes a ser 10 phosphoepitope on histone H3 to monitor H3 phosphorylation during meiosis in maize meiocytes. H3 phosphorylation has been reported to be an excellent marker for chromosome condensation during mitotic prophase in animal cells. In this study, we find that on maize mitotic chromosomes only pericentromeric regions are stained; there is little staining on the arms. During meiosis, chromosome condensation from leptotene through diplotene occurs in the absence of H3 phosphorylation. Instead, the changes in H3 phosphorylation at different stages of meiosis correlate with the differences in requirements for sister chromatid cohesion at different stages. Just before nuclear envelope breakdown, histone H3 phosphorylation is seen first in the pericentromeric regions and then extends through the arms at metaphase I; at metaphase II only the pericentromeric regions are stained. In afd1 (absence of first division), a mutant that is defective in many aspects of meiosis including sister chromatid cohesion and has equational separation at metaphase I, staining is restricted to the pericentromeric regions during metaphase I and anaphase I; there is no staining at metaphase II or anaphase II. We conclude that changes in the level of phosphorylation of ser10 in H3 correspond to changes in the cohesion of sister chromatids rather than the extent of chromosome condensation at different stages of meiosis.

scholarly journals Meiotic shugoshins differ from mitotic ones by arginine-reach C-terminal motif in yeast, plant, animals, and human

2016 ◽  
Author(s):  
Tatiana M Grishaeva ◽  
Darya Kulichenko ◽  
Yuri F Bogdanov
Keyword(s):  
Amino Acid ◽  
Structural Difference ◽  
Protein Molecule ◽  
Meiotic Metaphase ◽  
Chromosome Behavior ◽  
Sister Chromatids ◽  
Arginine Residues ◽  
The Difference ◽  
Mitosis And Meiosis ◽  
Metaphase I

Background. Shugoshins (SGOs) are proteins that protect cohesins located at the centromeres of sister chromatids from their early cleavage during mitosis and meiosis in plants, fungi, and animals. Their function is to prevent premature sister-chromatid disjunction and segregation. Meiotic SGOs prevent segregation of sister chromatids in meiosis I, thus permitting homologous chromosomes to segregate and reduce chromosome number to haploid set. The study focused on the structural differences among shugoshins acting during mitosis and meiosis that cause differences in chromosome behavior in these two types of cell division in different organisms. Methods. A bioinformatics analysis of protein domains, conserved amino acid motifs, and physicochemical properties of 32 proteins from 25 species of plants, fungi, and animals was performed. Results. We identified a C-terminal arginine-reach amino acid motif that is highly evolutionarily conserved among the shugoshins protecting centromere cohesion of sister chromatids in meiotic anaphase I, but not among mitotic shugoshins. The motif looks like “arginine comb” capable of interaction by hydrogen bonds with guanine bases in the small groove of DNA helix. Shugoshins in different eukaryotic kingdoms differ also in the sets and location of amino acid motifs and the number of α-helical regions in the protein molecule. Discussion. Meiosis-specific arginine-reach motif may be responsible for formation of SGO-DNA nucleoprotein complex, thus protecting meiotic shugoshins from degradation during meiotic metaphase I and anaphase I, while mitotic SGOs have a motif with less number of arginine residues. This structural difference between meiotic and mitotic shugoshins, probably, could be a key molecular element of the prolonged shugoshin resistance to degradation during meiotic metaphase I and anaphase I and be one of the molecular elements causing the difference in chromosome behavior in meiosis and mitosis. The finding of differences in SGO structure in plant, fungi and animals supports idea of independent evolution of meiosis in different lineages of multicellular organisms.

Phosphorylated proteins are involved in sister-chromatid arm cohesion during meiosis I

1999 ◽  
Vol 112 (17) ◽  
pp. 2957-2969 ◽  
Author(s):  
J.A. Suja ◽  
C. Antonio ◽  
A. Debec ◽  
J.S. Rufas
Keyword(s):  
Sister Chromatid ◽  
Chromosome Structure ◽  
Metaphase Plate ◽  
Mitotic Chromosomes ◽  
Phosphorylated Proteins ◽  
Sister Chromatids ◽  
Sequential Release ◽  
Sister Kinetochore ◽  
Meiosis I ◽  
Metaphase I

Sister-chromatid arm cohesion is lost during the metaphase I/anaphase I transition to allow homologue separation. To obtain needed information on this process we have analysed in grasshopper bivalents the sequential release of arm cohesion in relation to the behaviour of chromatid axes. Results show that sister axes are associated during early metaphase I but separate during late metaphase I leading to a concomitant change of chromosome structure that implies the loss of sister-kinetochore cohesion. Afterwards, homologues initiate their separation asynchronously depending on their size, and number and position of chiasmata. In all bivalents thin chromatin strands at the telomeres appeared as the last point of contact between sister chromatids. Additionally, we have analysed the participation of phosphoproteins recognised by the MPM-2 monoclonal antibody against mitotic phosphoproteins in arm cohesion in bivalents and two different kinds of univalents. Results show the absence of MPM-2 phosphoproteins at the interchromatid domain in mitotic chromosomes and meiotic univalents, but their presence in metaphase I bivalents. These phosphoproteins are lost at the onset of anaphase I. Taken together, these data have prompted us to propose a ‘working’ model for the release of arm cohesion during meiosis I. The model suggests that MPM-2 phosphoproteins may act as cohesive proteins associating sister axes. Their modification, once all bivalents are correctly aligned at the metaphase plate, would trigger a change of chromosome structure and the sequential release of sister-kinetochore, arm, and telomere cohesions.

scholarly journals Lateral Elements Inside Synaptonemal Complex-Like Polycomplexes in ndt80 Mutants of Yeast Bind DNA

Genetics ◽  
2003 ◽  
Vol 163 (2) ◽  
pp. 539-544 ◽  
Author(s):  
Hasanuzzaman Bhuiyan ◽  
Gunilla Dahlfors ◽  
Karin Schmekel
Keyword(s):  
In Situ Hybridization ◽  
Electron Microscope ◽  
Synaptonemal Complex ◽  
Immunoelectron Microscopy ◽  
Meiotic Prophase ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Meiotic Prophase I ◽  
Dna Antibodies

Abstract The synaptonemal complex (SC) keeps the synapsed homologous chromosomes together during pachytene in meiotic prophase I. Structures that resemble stacks of SCs, polycomplexes, are sometimes found before or after pachytene. We have investigated ndt80 mutants of yeast, which arrest in pachytene. SCs appear normal in spread chromosome preparations, but are only occasionally found in intact nuclei examined in the electron microscope. Instead, large polycomplexes occur in almost every ndt80 mutant nucleus. Immunoelectron microscopy using DNA antibodies show strong preferential labeling to the lateral element parts of the polycomplexes. In situ hybridization using chromosome-specific probes confirms that the chromosomes in ndt80 mutants are paired and attached to the SCs. Our results suggest that polycomplexes can be involved in binding of chromosomes and possibly also in synapsis.

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