scholarly journals Chromosome–nuclear envelope tethering – a process that orchestrates homologue pairing during plant meiosis?

2020 ◽  
Vol 133 (15) ◽  
pp. jcs243667
Author(s):  
Adél Sepsi ◽  
Trude Schwarzacher
Keyword(s):  
Nuclear Envelope ◽  
Chromosome Segregation ◽  
Higher Plants ◽  
Nuclear Periphery ◽  
Genetic Material ◽  
Strand Break ◽  
Genome Integrity ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Plant Meiosis

ABSTRACTDuring prophase I of meiosis, homologous chromosomes pair, synapse and exchange their genetic material through reciprocal homologous recombination, a phenomenon essential for faithful chromosome segregation. Partial sequence identity between non-homologous and heterologous chromosomes can also lead to recombination (ectopic recombination), a highly deleterious process that rapidly compromises genome integrity. To avoid ectopic exchange, homology recognition must be extended from the narrow position of a crossover-competent double-strand break to the entire chromosome. Here, we review advances on chromosome behaviour during meiotic prophase I in higher plants, by integrating centromere- and telomere dynamics driven by cytoskeletal motor proteins, into the processes of homologue pairing, synapsis and recombination. Centromere–centromere associations and the gathering of telomeres at the onset of meiosis at opposite nuclear poles create a spatially organised and restricted nuclear state in which homologous DNA interactions are favoured but ectopic interactions also occur. The release and dispersion of centromeres from the nuclear periphery increases the motility of chromosome arms, allowing meiosis-specific movements that disrupt ectopic interactions. Subsequent expansion of interstitial synapsis from numerous homologous interactions further corrects ectopic interactions. Movement and organisation of chromosomes, thus, evolved to facilitate the pairing process, and can be modulated by distinct stages of chromatin associations at the nuclear envelope and their collective release.

Maize meiotic spindles assemble around chromatin and do not require paired chromosomes

1998 ◽  
Vol 111 (23) ◽  
pp. 3507-3515 ◽  
Author(s):  
A. Chan ◽  
W.Z. Cande
Keyword(s):  
Nuclear Envelope ◽  
Higher Plants ◽  
Metaphase Plate ◽  
Meiotic Spindle ◽  
Wild Type ◽  
Homologous Chromosomes ◽  
Nuclear Envelope Breakdown ◽  
Meiotic Spindles ◽  
Meiotic Mutations ◽  
Bipolar Spindles

To understand how the meiotic spindle is formed and maintained in higher plants, we studied the organization of microtubule arrays in wild-type maize meiocytes and three maize meiotic mutants, desynaptic1 (dsy1), desynaptic2 (dsy2), and absence of first division (afd). All three meiotic mutations have abnormal chromosome pairing and produce univalents by diakinesis. Using these three mutants, we investigated how the absence of paired homologous chromosomes affects the assembly and maintenance of the meiotic spindle. Before nuclear envelope breakdown, in wild-type meiocytes, there were no bipolar microtubule arrays. Instead, these structures formed after nuclear envelope breakdown and were associated with the chromosomes. The presence of univalent chromosomes in dsy1, dsy2, and afd meiocytes and of unpaired sister chromatids in the afd meiocytes did not affect the formation of bipolar spindles. However, alignment of chromosomes on the metaphase plate and subsequent anaphase chromosome segregation were perturbed. We propose a model for spindle formation in maize meiocytes in which microtubules initially appear around the chromosomes during prometaphase and then the microtubules self-organize. However, this process does not require paired kinetochores to establish spindle bipolarity.

scholarly journals Speedy A–Cdk2 binding mediates initial telomere–nuclear envelope attachment during meiotic prophase I independent of Cdk2 activation

2016 ◽  
Vol 114 (3) ◽  
pp. 592-597 ◽  
Author(s):  
Zhaowei Tu ◽  
Mustafa Bilal Bayazit ◽  
Hongbin Liu ◽  
Jingjing Zhang ◽  
Kiran Busayavalasa ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Germ Cells ◽  
Meiotic Prophase ◽  
Homologous Pairing ◽  
Male And Female ◽  
Homologous Chromosomes ◽  
Cyclin Dependent Kinases ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Localization Domain

Telomere attachment to the nuclear envelope (NE) is a prerequisite for chromosome movement during meiotic prophase I that is required for pairing of homologous chromosomes, synapsis, and homologous recombination. Here we show that Speedy A, a noncanonical activator of cyclin-dependent kinases (Cdks), is specifically localized to telomeres in prophase I male and female germ cells in mice, and plays an essential role in the telomere–NE attachment. Deletion of Spdya in mice disrupts telomere–NE attachment, and this impairs homologous pairing and synapsis and leads to zygotene arrest in male and female germ cells. In addition, we have identified a telomere localization domain on Speedy A covering the distal N terminus and the Cdk2-binding Ringo domain, and this domain is essential for the localization of Speedy A to telomeres. Furthermore, we found that the binding of Cdk2 to Speedy A is indispensable for Cdk2’s localization on telomeres, suggesting that Speedy A and Cdk2 might be the initial components that are recruited to the NE for forming the meiotic telomere complex. However, Speedy A-Cdk2–mediated telomere–NE attachment is independent of Cdk2 activation. Our results thus indicate that Speedy A and Cdk2 might mediate the initial telomere–NE attachment for the efficient assembly of the telomere complex that is essential for meiotic prophase I progression.

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 The Unresolved Problem of DNA Bridging

Genes ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 623 ◽  
Author(s):  
María Fernández-Casañas ◽  
Kok-Lung Chan
Keyword(s):  
Chromosome Segregation ◽  
Genome Stability ◽  
Genetic Material ◽  
Genome Integrity ◽  
Cellular Division ◽  
Daughter Cells ◽  
Dna Replication And Repair ◽  
A Cell ◽  
Chromosome Separation ◽  
Last Stage

Accurate duplication and transmission of identical genetic information into offspring cells lies at the heart of a cell division cycle. During the last stage of cellular division, namely mitosis, the fully replicated DNA molecules are condensed into X-shaped chromosomes, followed by a chromosome separation process called sister chromatid disjunction. This process allows for the equal partition of genetic material into two newly born daughter cells. However, emerging evidence has shown that faithful chromosome segregation is challenged by the presence of persistent DNA intertwining structures generated during DNA replication and repair, which manifest as so-called ultra-fine DNA bridges (UFBs) during anaphase. Undoubtedly, failure to disentangle DNA linkages poses a severe threat to mitosis and genome integrity. This review will summarize the possible causes of DNA bridges, particularly sister DNA inter-linkage structures, in an attempt to explain how they may be processed and how they influence faithful chromosome segregation and the maintenance of genome stability.

scholarly journals Condensin suppresses recombination and regulates double-strand break processing at the repetitive ribosomal DNA array to ensure proper chromosome segregation during meiosis in budding yeast

2014 ◽  
Vol 25 (19) ◽  
pp. 2934-2947 ◽  
Author(s):  
Ping Li ◽  
Hui Jin ◽  
Hong-Guo Yu
Keyword(s):  
Chromosome Segregation ◽  
Ribosomal Dna ◽  
Meiotic Recombination ◽  
Budding Yeast ◽  
Strand Break ◽  
Double Strand Break ◽  
Prophase I ◽  
Rdna Array ◽  
Meiotic Dsbs ◽  
Rdna Copy

During meiosis, homologues are linked by crossover, which is required for bipolar chromosome orientation before chromosome segregation at anaphase I. The repetitive ribosomal DNA (rDNA) array, however, undergoes little or no meiotic recombination. Hyperrecombination can cause chromosome missegregation and rDNA copy number instability. We report here that condensin, a conserved protein complex required for chromosome organization, regulates double-strand break (DSB) formation and repair at the rDNA gene cluster during meiosis in budding yeast. Condensin is highly enriched at the rDNA region during prophase I, released at the prophase I/metaphase I transition, and reassociates with rDNA before anaphase I onset. We show that condensin plays a dual role in maintaining rDNA stability: it suppresses the formation of Spo11-mediated rDNA breaks, and it promotes DSB processing to ensure proper chromosome segregation. Condensin is unnecessary for the export of rDNA breaks outside the nucleolus but required for timely repair of meiotic DSBs. Our work reveals that condensin coordinates meiotic recombination with chromosome segregation at the repetitive rDNA sequence, thereby maintaining genome integrity.

scholarly journals OsMTOPVIB is required for meiotic bipolar spindle assembly

2019 ◽  
Vol 116 (32) ◽  
pp. 15967-15972 ◽  
Author(s):  
Zhihui Xue ◽  
Changzhen Liu ◽  
Wenqing Shi ◽  
Yongjie Miao ◽  
Yi Shen ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Chromosome Segregation ◽  
Spindle Assembly ◽  
Strand Break ◽  
Microtubule Assembly ◽  
Multipolar Spindle ◽  
Bipolar Spindle ◽  
Multipolar Spindles ◽  
Bipolar Spindles ◽  
Plant Meiosis

The organization of microtubules into a bipolar spindle is essential for chromosome segregation. Both centrosome and chromatin-dependent spindle assembly mechanisms are well studied in mouse, Drosophila melanogaster, and Xenopus oocytes; however, the mechanism of bipolar spindle assembly in plant meiosis remains elusive. According to our observations of microtubule assembly in Oryza sativa, Zea mays, Arabidopsis thaliana, and Solanum lycopersicum, we propose that a key step of plant bipolar spindle assembly is the correction of the multipolar spindle into a bipolar spindle at metaphase I. The multipolar spindles failed to transition into bipolar ones in OsmtopVIB with the defect in double-strand break (DSB) formation. However, bipolar spindles were normally assembled in several other mutants lacking DSB formation, such as Osspo11-1, pair2, and crc1, indicating that bipolar spindle assembly is independent of DSB formation. We further revealed that the mono-orientation of sister kinetochores was prevalent in OsmtopVIB, whereas biorientation of sister kinetochores was frequently observed in Osspo11-1, pair2, and crc1. In addition, mutations of the cohesion subunit OsREC8 resulted in biorientation of sister kinetochores as well as bipolar spindles even in the background of OsmtopVIB. Therefore, we propose that biorientation of the kinetochore is required for bipolar spindle assembly in the absence of homologous recombination.

scholarly journals Dissociation of membrane–chromatin contacts is required for proper chromosome segregation in mitosis

2019 ◽  
Vol 30 (4) ◽  
pp. 427-440 ◽  
Author(s):  
Lysie Champion ◽  
Sumit Pawar ◽  
Naemi Luithle ◽  
Rosemarie Ungricht ◽  
Ulrike Kutay
Keyword(s):  
Cell Division ◽  
Nuclear Envelope ◽  
Chromosome Segregation ◽  
Nuclear Periphery ◽  
Metaphase Plate ◽  
Chromatin Organization ◽  
Mitotic Entry ◽  
Chromatin Interactions ◽  
Membrane Attachment ◽  
Mitotic Chromatin

The nuclear envelope (NE) aids in organizing the interphase genome by tethering chromatin to the nuclear periphery. During mitotic entry, NE–chromatin contacts are broken. Here, we report on the consequences of impaired NE removal from chromatin for cell division of human cells. Using a membrane–chromatin tether that cannot be dissociated when cells enter mitosis, we show that a failure in breaking membrane–chromatin interactions impairs mitotic chromatin organization, chromosome segregation and cytokinesis, and induces an aberrant NE morphology in postmitotic cells. In contrast, chromosome segregation and cell division proceed successfully when membrane attachment to chromatin is induced during metaphase, after chromosomes have been singularized and aligned at the metaphase plate. These results indicate that the separation of membranes and chromatin is critical during prometaphase to allow for proper chromosome compaction and segregation. We propose that one cause of these defects is the multivalency of membrane–chromatin interactions.

scholarly journals The Laminopathies and the Insights They Provide into the Structural and Functional Organization of the Nucleus

2020 ◽  
Vol 21 (1) ◽  
pp. 263-288 ◽  
Author(s):  
Xianrong Wong ◽  
Colin L. Stewart
Keyword(s):  
Health Care ◽  
Nuclear Envelope ◽  
Functional Organization ◽  
Nuclear Periphery ◽  
Genetic Material ◽  
Cytoskeletal Organization ◽  
Functional Roles ◽  
Storage Organelle ◽  
Transcriptional Output ◽  
Contemporary Health Care

In recent years, our perspective on the cell nucleus has evolved from the view that it is a passive but permeable storage organelle housing the cell's genetic material to an understanding that it is in fact a highly organized, integrative, and dynamic regulatory hub. In particular, the subcompartment at the nuclear periphery, comprising the nuclear envelope and the underlying lamina, is now known to be a critical nexus in the regulation of chromatin organization, transcriptional output, biochemical and mechanosignaling pathways, and, more recently, cytoskeletal organization. We review the various functional roles of the nuclear periphery and their deregulation in diseases of the nuclear envelope, specifically the laminopathies, which, despite their rarity, provide insights into contemporary health-care issues.

scholarly journals Telomere tethering at the nuclear periphery is essential for efficient DNA double strand break repair in subtelomeric region

2006 ◽  
Vol 172 (2) ◽  
pp. 189-199 ◽  
Author(s):  
Pierre Therizols ◽  
Cécile Fairhead ◽  
Ghislain G. Cabal ◽  
Auguste Genovesio ◽  
Jean-Christophe Olivo-Marin ◽  
...  
Keyword(s):  
Functional Organization ◽  
Nuclear Periphery ◽  
Strand Break ◽  
Double Strand Break ◽  
Subtelomeric Region ◽  
Genome Integrity ◽  
Nuclear Pore ◽  
Core Complex ◽  
Yeast Saccharomyces Cerevisiae ◽  
Dna Double Strand Break

In the yeast Saccharomyces cerevisiae that lacks lamins, the nuclear pore complex (NPC) has been proposed to serve a role in chromatin organization. Here, using fluorescence microscopy in living cells, we show that nuclear pore proteins of the Nup84 core complex, Nup84p, Nup145Cp, Nup120p, and Nup133p, serve to anchor telomere XI-L at the nuclear periphery. The integrity of this complex is shown to be required for repression of a URA3 gene inserted in the subtelomeric region of this chromosome end. Furthermore, altering the integrity of this complex decreases the efficiency of repair of a DNA double-strand break (DSB) only when it is generated in the subtelomeric region, even though the repair machinery is functional. These effects are specific to the Nup84 complex. Our observations thus confirm and extend the role played by the NPC, through the Nup84 complex, in the functional organization of chromatin. They also indicate that anchoring of telomeres is essential for efficient repair of DSBs occurring therein and is important for preserving genome integrity.

Factors directing telomere dynamics in synaptic meiosis

2006 ◽  
Vol 34 (4) ◽  
pp. 550-553 ◽  
Author(s):  
H. Scherthan
Keyword(s):  
Nuclear Envelope ◽  
Budding Yeast ◽  
S Phase ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Yeast Meiosis ◽  
Bouquet Stage ◽  
Different Levels ◽  
Telomere Dynamics ◽  
Meiosis I

Meiosis creates haploid cells from diploid progenitors. Homologous chromosomes are moved, paired and segregated from each other in a specialized meiosis I division. A second division that lacks a preceding S-phase produces haploid cells. In prophase I, chromosomes attach with their telomeres to the nuclear envelope and undergo oscillating movements that become restricted to a limited nuclear sector during the widely conserved bouquet stage. Recent observations in budding yeast meiosis suggest that telomere clustering depends on actin, whereas exit from the bouquet stage requires meiotic cohesin. Telomere clustering may also be modulated by progression in recombination. These observations suggest that the unique meiotic nuclear topology and telomere dynamics are regulated at different levels.

Sign in / Sign up

Export Citation Format

Share Document