scholarly journals Dynamics of chromosome organization and pairing during meiotic prophase in fission yeast.

1994 ◽  
Vol 127 (2) ◽  
pp. 273-285 ◽  
Author(s):  
H Scherthan ◽  
J Bähler ◽  
J Kohli
Keyword(s):  
Meiotic Prophase ◽  
Regional Differences ◽  
Chromosome Organization ◽  
Central Importance ◽  
Homologous Chromosomes ◽  
Meiotic Chromosomes ◽  
Hybridization Probes ◽  
Linear Elements ◽  
Axial Element

Interactions between homologous chromosomes (pairing, recombination) are of central importance for meiosis. We studied entire chromosomes and defined chromosomal subregions in synchronous meiotic cultures of Schizosaccharomyces pombe by fluorescence in situ hybridization. Probes of different complexity were applied to spread nuclei, to delineate whole chromosomes, to visualize repeated sequences of centromeres, telomeres, and ribosomal DNA, and to study unique sequences of different chromosomal regions. In diploid nuclei, homologous chromosomes share a joint territory even before entry into meiosis. The centromeres of all chromosomes are clustered in vegetative and meiotic prophase cells, whereas the telomeres cluster near the nucleolus early in meiosis and maintain this configuration throughout meiotic prophase. Telomeres and centromeres appear to play crucial roles for chromosome organization and pairing, both in vegetative cells and during meiosis. Homologous pairing of unique sequences shows regional differences and is most frequent near centromeres and telomeres. Multiple homologous interactions are formed independently of each other. Pairing increases during meiosis, but not all chromosomal regions become closely paired in every meiosis. There is no detectable axial compaction of chromosomes in meiotic prophase. S. pombe does not form mature synaptonemal complexes, but axial element-like structures (linear elements), which were analyzed in parallel. Their appearance coincides with pairing of interstitial chromosomal regions. Axial elements may define minimal structures required for efficient pairing and recombination of meiotic chromosomes.

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.

scholarly journals Mammalian Protein SCP1 Forms Synaptonemal Complex-like Structures in the Absence of Meiotic Chromosomes

2005 ◽  
Vol 16 (1) ◽  
pp. 212-217 ◽  
Author(s):  
Rupert Öllinger ◽  
Manfred Alsheimer ◽  
Ricardo Benavente
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Prophase ◽  
Experimental Conditions ◽  
Homologous Chromosomes ◽  
Meiotic Chromosomes ◽  
Heterologous System ◽  
Primary Determinant ◽  
Specific Proteins ◽  
Mammalian Protein

Synaptonemal complexes (SCs) are evolutionary conserved, meiosis-specific structures that play a central role in synapsis of homologous chromosomes, chiasmata distribution, and chromosome segregation. However, it is still for the most part unclear how SCs do assemble during meiotic prophase. Major components of mammalian SCs are the meiosis-specific proteins SCP1, 2, and 3. To investigate the role of SCP1 in SC assembly, we expressed SCP1 in a heterologous system, i.e., in COS-7 cells that normally do not express SC proteins. Notably, under these experimental conditions SCP1 is able to form structures that closely resemble SCs (i.e., polycomplexes). Moreover, we show that mutations that modify the length of the central α-helical domain of SCP1 influence the width of polycomplexes. Finally, we demonstrate that deletions of the nonhelical N- or C-termini both affect polycomplex assembly, although in a different manner. We conclude that SCP1 is a primary determinant of SC assembly that plays a key role in synapsis of homologous chromosomes.

scholarly journals DNase I nick translation in situ on meiotic chromosomes of the mouse, Mus musculus

1988 ◽  
Vol 90 (4) ◽  
pp. 629-634
Author(s):  
R. Raman ◽  
A.P. Singh ◽  
I. Nanda
Keyword(s):  
Sex Chromosomes ◽  
Mus Musculus ◽  
Meiotic Prophase ◽  
Cell Types ◽  
Dnase I ◽  
Translation Method ◽  
Nick Translation ◽  
Meiotic Chromosomes

DNase-I-sensitive sites have been located on the meiotic chromosomes of the mouse, Mus musculus, by the in situ DNase I nick-translation method. We find that: (1) of all the cell types studied, pachytene nuclei are the most sensitive to DNase I; (2) in diplotene the nicks occur preferentially in the vicinity of chiasmata; (3) the sex chromosomes are also sensitive to the enzyme despite their transcriptional quiescence; and (4) in the sex bivalent the nicks are primarily observed in the putative region of recombination. We conclude that, in addition to discriminating between the transcriptionally active and inactive states of chromatin, DNase I identifies recombination-specific chromatin changes in meiotic prophase.

scholarly journals Meiosis-specific prophase-like pathway controls cleavage-independent release of cohesin by Wapl phosphorylation

2018 ◽  
Author(s):  
Kiran Challa ◽  
V Ghanim Fajish ◽  
Miki Shinohara ◽  
Franz Klein ◽  
Susan M. Gasser ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Meiotic Prophase ◽  
Budding Yeast ◽  
Cell Cycle Regulators ◽  
Late Prophase ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Meiotic Chromosomes

AbstractSister chromatid cohesion on chromosome arms is essential for the segregation of homologous chromosomes during meiosis I while it is dispensable for sister chromatid separation during mitosis. It was assumed that, unlike the situation in mitosis, chromosome arms retain cohesion prior to onset of anaphase-I. Paradoxically, reduced immunostaining signals of meiosis-specific cohesin, including the kleisin Rec8, from the chromosomes were observed during late prophase-I of budding yeast. This decrease is seen in the absence of Rec8 cleavage and depends on condensin-mediated recruitment of Polo-like kinase (PLK/Cdc5). In this study, we confirmed that this release indeed accompanies the dissociation of acetylated Smc3 as well as Rec8 from meiotic chromosomes during late prophase-I. This release requires, in addition to PLK, the cohesin regulator, Wapl (Rad61/Wpl1 in yeast), and Dbf4-dependent Cdc7 kinase (DDK). Meiosis-specific phosphorylation of Rad61/Wpl1 and Rec8 by PLK and DDK collaboratively promote this release. This process is similar to the vertebrate “prophase” pathway for cohesin release during G2 phase and pro-metaphase. In yeast, meiotic cohesin release coincides with PLK-dependent compaction of chromosomes in late meiotic prophase-I. We suggest that yeast uses this highly regulated cleavage-independent pathway to remove cohesin during late prophase-I to facilitate morphogenesis of condensed metaphase-I chromosomes.Author SummaryIn meiosis the life and health of future generations is decided upon. Any failure in chromosome segregation has a detrimental impact. Therefore, it is currently believed that the physical connections between homologous chromosomes are maintained by meiotic cohesin with exceptional stability. Indeed, it was shown that cohesive cohesin does not show an appreciable turnover during long periods in oocyte development. In this context, it was long assumed but not properly investigated, that the prophase pathway for cohesin release would be specific to mitotic cells and will be safely suppressed during meiosis so as not to endanger the valuable chromosome connections. However, a previous study on budding yeast meiosis suggests the presence of cleavage-independent pathway of cohesin release during late prophase-I. In the work presented here we confirmed that the prophase pathway is not suppressed during meiosis, at least in budding yeast and showed that this cleavage-independent release is regulated by meiosis-specific phosphorylation of two cohesin subunits, Rec8 and Rad61(Wapl) by two cell-cycle regulators, PLK and DDK. Our results suggest that late meiotic prophase-I actively controls cohesin dynamics on meiotic chromosomes for chromosome segregation.

scholarly journals Micromanipulation of prophase I chromosomes from mouse spermatocytes reveals high stiffness and gel-like chromatin organization

2020 ◽  
Author(s):  
Ronald Biggs ◽  
Ning Liu ◽  
Yiheng Peng ◽  
John F. Marko ◽  
Huanyu Qiao
Keyword(s):  
Meiotic Prophase ◽  
Central Element ◽  
Critical Event ◽  
Mitotic Chromosomes ◽  
Large Protein ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Meiotic Chromosomes ◽  
Genetic Mutants

Meiosis produces four haploid cells after two successive divisions in sexually reproducing organisms. A critical event during meiosis is construction of the synaptonemal complex (SC), a large, protein-based bridge that physically links homologous chromosomes. The SC facilitates meiotic recombination, chromosome compaction, and the eventual separation of homologous chromosomes at metaphase I. We present experiments directly measuring physical properties of captured mammalian meiotic prophase I chromosomes. Mouse meiotic chromosomes are about ten-fold stiffer than somatic mitotic chromosomes, even for genetic mutants lacking SYCP1, the central element of the SC. Meiotic chromosomes dissolve when treated with nucleases, but only weaken when treated with proteases, suggesting that the SC is not rigidly connected, and that meiotic prophase I chromosomes are a gel meshwork of chromatin, similar to mitotic chromosomes. These results are consistent with a liquid- or liquid-crystal SC, but with SC-chromatin stiff enough to mechanically drive crossover interference.

scholarly journals The rec8 gene of Schizosaccharomyces pombe is involved in linear element formation, chromosome pairing and sister-chromatid cohesion during meiosis.

Genetics ◽  
1995 ◽  
Vol 141 (1) ◽  
pp. 61-73
Author(s):  
M Molnar ◽  
J Bähler ◽  
M Sipiczki ◽  
J Kohli
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Chromosome Pairing ◽  
Meiotic Recombination ◽  
Meiotic Prophase ◽  
Meiotic Chromosome ◽  
Linear Element ◽  
Meiotic Chromosomes ◽  
Sister Chromatids ◽  
Linear Elements ◽  
Chromosome Iii

Abstract The fission yeast Schizosaccharomyces pombe does not form tripartite synaptonemal complexes during meiotic prophase, but axial core-like structures (linear elements). To probe the relationship between meiotic recombination and the structure, pairing, and segregation of meiotic chromosomes, we genetically and cytologically characterized the rec8-110 mutant, which is partially deficient in meiotic recombination. The pattern of spore viability indicates that chromosome segregation is affected in the mutant. A detailed segregational analysis in the rec8-110 mutant revealed more spores disomic for chromosome III than in a wild-type strain. Aberrant segregations are caused by precocious segregation of sister chromatids at meiosis I, rather than by nondisjunction as a consequence of lack of crossovers. In situ hybridization further showed that the sister chromatids are separated prematurely during meiotic prophase. Moreover, the mutant forms aberrant linear elements and shows a shortened meiotic prophase. Meiotic chromosome pairing in interstitial and centromeric regions is strongly impaired in rec8-110, whereas the chromosome ends are less deficient in pairing. We propose that the rec8 gene encodes a protein required for linear element formation and that the different phenotypes of rec8-110 reflect direct and indirect consequences of the absence of regular linear elements.

scholarly journals Micromanipulation of prophase I chromosomes from mouse spermatocytes reveals high stiffness and gel-like chromatin organization

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Ronald J. Biggs ◽  
Ning Liu ◽  
Yiheng Peng ◽  
John F. Marko ◽  
Huanyu Qiao
Keyword(s):  
Meiotic Prophase ◽  
Central Element ◽  
Critical Event ◽  
Mitotic Chromosomes ◽  
Large Protein ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Meiotic Chromosomes ◽  
Genetic Mutants

Abstract Meiosis produces four haploid cells after two successive divisions in sexually reproducing organisms. A critical event during meiosis is construction of the synaptonemal complex (SC), a large, protein-based bridge that physically links homologous chromosomes. The SC facilitates meiotic recombination, chromosome compaction, and the eventual separation of homologous chromosomes at metaphase I. We present experiments directly measuring physical properties of captured mammalian meiotic prophase I chromosomes. Mouse meiotic chromosomes are about ten-fold stiffer than somatic mitotic chromosomes, even for genetic mutants lacking SYCP1, the central element of the SC. Meiotic chromosomes dissolve when treated with nucleases, but only weaken when treated with proteases, suggesting that the SC is not rigidly connected, and that meiotic prophase I chromosomes are a gel meshwork of chromatin, similar to mitotic chromosomes. These results are consistent with a liquid- or liquid-crystal SC, but with SC-chromatin stiff enough to mechanically drive crossover interference.

Identical megabase transgenes on mouse chromosomes 3 and 4 do not promote ectopic pairing or synapsis at meiosis

Genome ◽  
1997 ◽  
Vol 40 (5) ◽  
pp. 770-773 ◽  
Author(s):  
P. B. Moens ◽  
J. A. M. Heddle ◽  
B. Spyropoulos ◽  
H. H. Q. Heng
Keyword(s):  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Nuclear Volume ◽  
Dna Interactions ◽  
Synaptonemal Complexes ◽  
Meiotic Chromosomes ◽  
Ectopic Pairing

To investigate ectopic interactions at the chromatin level, we examined the meiotic organization of 1–2 mb phage λ transgenes on mouse chromosomes 3 and 4 by fluorescence in situ hybridization in combination with immunocytology of meiotic chromosomes. At early meiotic prophase, the transgenes are sufficiently dispersed in the nuclear volume to permit potential DNA–DNA interactions, but no synaptonemal complexes form between the sites of transgenes residing on different chromosomes. At later stages, when the chromatin is more condensed, the transgenes on different chromosomes are not preferentially associated as they are when they are on the same chromosome. At diplotene and metaphase I, no formations were observed that could be interpreted as reciprocal crossovers or chiasmata between the transgenes located on chromosomes 3 and 4. It appears that in normal fertile mice, a 1- to 2-mb homology is insufficient to initiate synapsis between nonhomologs, and it is concluded that homology is assessed within the broader context of the chromosome to initiate synapsis at meiotic prophase.Key words: transgenes, ectopic pairing, meiosis, synaptonemal complex, immunocytology, FISH.

Spectral karyotyping (SKY) of mouse meiotic chromosomes

Genome ◽  
2001 ◽  
Vol 44 (2) ◽  
pp. 293-298 ◽  
Author(s):  
Henry HQ Heng ◽  
Guo Liu ◽  
Wei Lu ◽  
Steve Bremer ◽  
Christine J Ye ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Spectral Karyotyping ◽  
Mitotic Chromosomes ◽  
Meiotic Chromosomes ◽  
Y Chromosomes ◽  
Behavioural Characteristics ◽  
Co Detection

The spectral karyotyping procedure of in situ hybridization with chromosome-specific probes assigns a unique colour code to each of the 21 mouse mitotic chromosomes. We have adapted this procedure to meiotic prophase chromosomes, and the results show that each of the pachytene or metaphase I bivalents can be identified. This technique has the potential to recognize synaptic anomalies and chromosome-specific structural and behavioural characteristics. We confirm these potentials by the recognition of the heterologous synapsis of the X and Y chromosomes and by the variances of synaptonemal complex lengths for each of the colour-coded bivalents in eight prophase nuclei.Key words: SKY, meiosis, synaptonemal complex, multicolour, chromosome painting, spectral karyotyping, protein-SKY co-detection.

Rec8 cohesin-mediated loop-axis chromatin architecture is required for meiotic recombination

2021 ◽  
Author(s):  
Takeshi Sakuno ◽  
Sanki Tashiro ◽  
Hideki Tanizawa ◽  
Osamu Iwasaki ◽  
Da-Qiao Ding ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Synaptonemal Complex ◽  
Meiotic Recombination ◽  
Meiotic Prophase ◽  
Essential Role ◽  
Homologous Chromosomes ◽  
Functional Correlation ◽  
Chromatin Architecture ◽  
Central Elements ◽  
Linear Elements

During meiotic prophase, cohesin-dependent axial structures are formed in the synaptonemal complex (SC). However, the functional correlation between these structures and cohesion remains elusive. Here, we examined the formation of the cohesin-dependent axial structure in fission yeast, which forms atypical SCs composed of linear elements (LinEs) resembling the lateral elements of SC but lacking the central elements. The results demonstrated that Rec8 cohesin is crucial for the formation of the loop-axis structure within the atypical SC. Furthermore, the Rec8-mediated loop-axis structure is formed in the absence of LinEs and provides a structural platform for aligning homologous chromosomes. We also identified a rec8 mutant that lost the ability to assemble the loop-axis structure without losing cohesion. Remarkably, this mutant showed defects in the LinE assembly, resulting in a significant reduction in meiotic recombination. Collectively, our results demonstrate an essential role for the Rec8-dependent loop-axis structure in LinE assembly, facilitating meiotic recombination.

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