scholarly journals Meiotic Chromosome Interactions: Nonhomologous Centromere (Un)Coupling and Homologous Synapsis

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Amit Bardhan
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Regulatory Network ◽  
Meiotic Chromosome ◽  
Fundamental Function ◽  
Homologous Chromosomes ◽  
Reciprocal Recombination

The fundamental function of meiosis, segregation of the maternal and paternal chromosomes, is facilitated by reciprocal recombination and intimate juxtaposition (synapsis) between the homologous chromosomes in meiotic prophase. Homolog synapsis, mediated by the synaptonemal complex (SC), is preceded by a stage of pairing between the centromeres of nonhomologous chromosomes. This pairing, named nonhomologous centromere coupling (NCC), depends upon the meiotic cohesin Rec8 and the SC protein Zip1. Nonhomologously coupled centromeres (NCCs), if remain tethered, must interfere with complete homolog synapsis (SC formation). Recent experiments demonstrate the existence of a mechanism that regulates NCC. Importantly, this is part of a regulatory network which couples dissolution of the NCCs with SC formation between the homologous chromosomes, thereby ensuring appropriate meiotic chromosome interactions. This paper reviews this network and presents speculations relating to the initiation of SC formation at centromere.

scholarly journals Shugoshin protects centromere pairing and promotes segregation of non-exchange partner chromosomes in meiosis

2018 ◽  
Author(s):  
Luciana Previato de Almeida ◽  
Jared M. Evatt ◽  
Hoa H. Chuong ◽  
Emily L. Kurdzo ◽  
Craig A. Eyster ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Meiotic Prophase ◽  
Single Unit ◽  
Meiotic Chromosome ◽  
Model Systems ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Meiosis I

ABSTRACTFaithful chromosome segregation during meiosis I depends upon the formation of connections between homologous chromosomes. Crossovers between homologs connect the partners allowing them to attach to the meiotic spindle as a unit, such that they migrate away from one another at anaphase I. Homologous partners also become connected by pairing of their centromeres in meiotic prophase. This centromere pairing can promote proper segregation at anaphase I of partners that have failed to become joined by a crossover. Centromere pairing is mediated by synaptonemal complex (SC) proteins that persist at the centromere when the SC disassembles. Here, using mouse spermatocyte and yeast model systems, we tested the role of shugoshin in promoting meiotic centromere pairing by protecting centromeric synaptonemal components from disassembly. The results show that shugoshin protects centromeric SC in meiotic prophase and, in anaphase, promotes the proper segregation of partner chromosomes that are not linked by a crossover.SIGNIFICANCEMeiotic crossovers form a connection between homologous chromosomes that allows them to attach to the spindle as a single unit in meiosis I. In humans, failures in this process are a leading cause of aneuploidy. A recently described process, called centromere pairing, can also help connect meiotic chromosome partners in meiosis. Homologous chromosomes become tightly joined by a structure called the synaptonemal complex (SC) in meiotic prophase. After the SC disassembles, persisting SC proteins at the centromeres mediate their pairing. Here, studies in mouse spermatocytes and yeast are used to show that the shugoshin protein helps SC components persist at centromeres and helps centromere pairing promote the proper segregation of yeast chromosomes that fail to become tethered by crossovers.

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 Crossing over is coupled to late meiotic prophase bivalent differentiation through asymmetric disassembly of the SC

2005 ◽  
Vol 168 (5) ◽  
pp. 683-689 ◽  
Author(s):  
Kentaro Nabeshima ◽  
Anne M. Villeneuve ◽  
Monica P. Colaiácovo
Keyword(s):  
Caenorhabditis Elegans ◽  
Symmetry Breaking ◽  
Synaptonemal Complex ◽  
Central Region ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Meiotic Chromosome ◽  
Crossing Over ◽  
Γ Irradiation ◽  
Irradiation Treatment

Homologous chromosome pairs (bivalents) undergo restructuring during meiotic prophase to convert a configuration that promotes crossover recombination into one that promotes bipolar spindle attachment and localized cohesion loss. We have imaged remodeling of meiotic chromosome structures after pachytene exit in Caenorhabditis elegans. Chromosome shortening during diplonema is accompanied by coiling of chromosome axes and highly asymmetric departure of synaptonemal complex (SC) central region proteins SYP-1 and SYP-2, which diminish over most of the length of each desynapsing bivalent while becoming concentrated on axis segments distal to the single emerging chiasma. This and other manifestations of asymmetry along chromosomes are lost in synapsis-proficient crossover-defective mutants, which often retain SYP-1,2 along the full lengths of coiled diplotene axes. Moreover, a γ-irradiation treatment that restores crossovers in the spo-11 mutant also restores asymmetry of SYP-1 localization. We propose that crossovers or crossover precursors serve as symmetry-breaking events that promote differentiation of subregions of the bivalent by triggering asymmetric disassembly of the SC.

scholarly journals akirin is required for diakinesis bivalent structure and synaptonemal complex disassembly at meiotic prophase I

2013 ◽  
Vol 24 (7) ◽  
pp. 1053-1067 ◽  
Author(s):  
Amy M. Clemons ◽  
Heather M. Brockway ◽  
Yizhi Yin ◽  
Bhavatharini Kasinathan ◽  
Yaron S. Butterfield ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Chromosome Condensation ◽  
Late Prophase ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Evolutionarily Conserved ◽  
Key Events

During meiosis, evolutionarily conserved mechanisms regulate chromosome remodeling, leading to the formation of a tight bivalent structure. This bivalent, a linked pair of homologous chromosomes, is essential for proper chromosome segregation in meiosis. The formation of a tight bivalent involves chromosome condensation and restructuring around the crossover. The synaptonemal complex (SC), which mediates homologous chromosome association before crossover formation, disassembles concurrently with increased condensation during bivalent remodeling. Both chromosome condensation and SC disassembly are likely critical steps in acquiring functional bivalent structure. The mechanisms controlling SC disassembly, however, remain unclear. Here we identify akir-1 as a gene involved in key events of meiotic prophase I in Caenorhabditis elegans. AKIR-1 is a protein conserved among metazoans that lacks any previously known function in meiosis. We show that akir-1 mutants exhibit severe meiotic defects in late prophase I, including improper disassembly of the SC and aberrant chromosome condensation, independently of the condensin complexes. These late-prophase defects then lead to aberrant reconfiguring of the bivalent. The meiotic divisions are delayed in akir-1 mutants and are accompanied by lagging chromosomes. Our analysis therefore provides evidence for an important role of proper SC disassembly in configuring a functional bivalent structure.

scholarly journals Synaptonemal complex components are required for meiotic checkpoint function in C. elegans

2016 ◽  
Author(s):  
Tisha Bohr ◽  
Guinevere Ashley ◽  
Evan Eggleston ◽  
Kyra Firestone ◽  
Needhi Bhalla
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Meiotic Chromosome ◽  
Checkpoint Response ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Homolog Pairing ◽  
The Stability ◽  
Complex Components

AbstractSynapsis involves the assembly of a proteinaceous structure, the synaptonemal complex (SC), between paired homologous chromosomes and is essential for proper meiotic chromosome segregation. In C. elegans, the synapsis checkpoint selectively removes nuclei with unsynapsed chromosomes by inducing apoptosis. This checkpoint depends on Pairing Centers (PCs), cis-acting sites that promote pairing and synapsis. We have hypothesized that the stability of homolog pairing at PCs is monitored by this checkpoint. Here, we report that SC components SYP-3, HTP-3, HIM-3 and HTP-1 are required for a functional synapsis checkpoint. Mutation of these components does not abolish PC function, demonstrating they are bonafide checkpoint components. Further, we identify mutant backgrounds in which the instability of homolog pairing at PCs does not correlate with the synapsis checkpoint response. Altogether, these data suggest that, in addition to homolog pairing, SC assembly may be monitored by the synapsis checkpoint.

scholarly journals SCF-Fbxo42 promotes synaptonemal complex assembly by downregulating PP2A-B56

2020 ◽  
Vol 220 (2) ◽  
Author(s):  
Pedro Barbosa ◽  
Liudmila Zhaunova ◽  
Simona Debilio ◽  
Verdiana Steccanella ◽  
Van Kelly ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Synaptonemal Complex ◽  
Ubiquitin Ligase ◽  
Posttranslational Modifications ◽  
Meiotic Prophase ◽  
Female Meiosis ◽  
Complex Assembly ◽  
Homologous Chromosomes ◽  
Ubiquitin Ligase Complex ◽  
Segregation Of Chromosomes

Meiosis creates genetic diversity by recombination and segregation of chromosomes. The synaptonemal complex assembles during meiotic prophase I and assists faithful exchanges between homologous chromosomes, but how its assembly/disassembly is regulated remains to be understood. Here, we report how two major posttranslational modifications, phosphorylation and ubiquitination, cooperate to promote synaptonemal complex assembly. We found that the ubiquitin ligase complex SCF is important for assembly and maintenance of the synaptonemal complex in Drosophila female meiosis. This function of SCF is mediated by two substrate-recognizing F-box proteins, Slmb/βTrcp and Fbxo42. SCF-Fbxo42 down-regulates the phosphatase subunit PP2A-B56, which is important for synaptonemal complex assembly and maintenance.

Coordinating the segregation of sister chromatids during the first meiotic division: evidence for sexual dimorphism

2001 ◽  
Vol 114 (13) ◽  
pp. 2417-2426 ◽  
Author(s):  
Craig A. Hodges ◽  
Renée LeMaire-Adkins ◽  
Patricia A. Hunt
Keyword(s):  
Sexual Dimorphism ◽  
Synaptonemal Complex ◽  
X Chromosome ◽  
Meiotic Division ◽  
Meiotic Chromosome ◽  
Female Meiosis ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Chromatid Segregation ◽  
Protein Components

Errors during the first meiotic division are common in our species, but virtually all occur during female meiosis. The reason why oogenesis is more error prone than spermatogenesis remains unknown. Normal segregation of homologous chromosomes at the first meiotic division (MI) requires coordinated behavior of the sister chromatids of each homolog. Failure of sister kinetochores to act cooperatively at MI, or precocious sister chromatid segregation (PSCS), has been postulated to be a major contributor to human nondisjunction. To investigate the factors that influence PSCS we utilized the XO mouse, since the chromatids of the single X chromosome frequently segregate at MI, and the propensity for PSCS is influenced by genetic background. Our studies demonstrate that the strain-specific differences in PSCS are due to the actions of an autosomal trans-acting factor or factors. Since components of the synaptonemal complex are thought to play a role in centromere cohesion and kinetochore orientation, we evaluated the behavior of the X chromosome at prophase to determine if this factor influenced the propensity of the chromosome for self-synapsis. We were unable to directly correlate synaptic differences with subsequent segregation behavior. However, unexpectedly, we uncovered a sexual dimorphism that may partially explain sex-specific differences in the fidelity of meiotic chromosome segregation. Specifically, in the male remnants of the synaptonemal complex remain associated with the centromeres until anaphase of the second meiotic division (MII), whereas in the female, all traces of synaptonemal complex (SC) protein components are lost from the chromosomes before the onset of the first meiotic division. This finding suggests a sex-specific difference in the components used to correctly segregate chromosomes during meiosis, and may provide a reason for the high error frequency during female meiosis.

Hendrik Peter Bernelot Moens (1931–2008)

Genome ◽  
2008 ◽  
Vol 51 (12) ◽  
pp. 1063-1067 ◽  
Author(s):  
Edyta Marcon
Keyword(s):  
North Carolina ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Structural Characteristics ◽  
Specific Structure ◽  
Homologous Chromosomes ◽  
Time Points ◽  
Duke University ◽  
Protein Components ◽  
Functional Components

The synaptonemal complex (SC) is a proteinaceous structure that physically holds the two homologous chromosomes together during meiotic prophase. First observed in 1956 by Montrose J. Moses (Duke University, Durham, North Carolina) in meiotic prophase spermatocytes of crayfish, the SC was found in many other species. Initially, the research into the SC focused on its structural characteristics, but with the availability of antibodies, the focus shifted to the protein components of the complex, and later, attention was diverted to the proteins associated with this structure at different time points during meiotic prophase. Various possible roles of this meiotic-specific structure have been debated since the discovery of the SC structure but consensus has yet to be reached. Dr. Peter Moens has been an internationally recognized expert on the SC, being involved in all of the steps and characterizing many of the structural and functional components of the complex mainly in mice but also in other species.

scholarly journals Shugoshin protects centromere pairing and promotes segregation of nonexchange partner chromosomes in meiosis

2019 ◽  
Vol 116 (19) ◽  
pp. 9417-9422 ◽  
Author(s):  
Luciana Previato de Almeida ◽  
Jared M. Evatt ◽  
Hoa H. Chuong ◽  
Emily L. Kurdzo ◽  
Craig A. Eyster ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Meiotic Prophase ◽  
Model Systems ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Meiosis I ◽  
Yeast Model

Faithful chromosome segregation during meiosis I depends upon the formation of connections between homologous chromosomes. Crossovers between homologs connect the partners, allowing them to attach to the meiotic spindle as a unit, such that they migrate away from one another at anaphase I. Homologous partners also become connected by pairing of their centromeres in meiotic prophase. This centromere pairing can promote proper segregation at anaphase I of partners that have failed to become joined by a crossover. Centromere pairing is mediated by synaptonemal complex (SC) proteins that persist at the centromere when the SC disassembles. Here, using mouse spermatocyte and yeast model systems, we tested the role of shugoshin in promoting meiotic centromere pairing by protecting centromeric synaptonemal components from disassembly. The results show that shugoshin protects the centromeric SC in meiotic prophase and, in anaphase, promotes the proper segregation of partner chromosomes that are not linked by a crossover.

scholarly journals Meiotic Chromosome Contacts as a Plausible Prelude for Robertsonian Translocations

Genes ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 386 ◽  
Author(s):  
Sergey Matveevsky ◽  
Oxana Kolomiets ◽  
Aleksey Bogdanov ◽  
Elena Alpeeva ◽  
Irina Bakloushinskaya
Keyword(s):  
Meiotic Prophase ◽  
Meiotic Chromosome ◽  
Immunocytochemical Staining ◽  
Robertsonian Translocations ◽  
Homologous Chromosomes ◽  
Mechanism Model ◽  
Prophase I ◽  
Meiotic Prophase I ◽  
Translocation Mechanism ◽  
Mole Vole

Robertsonian translocations are common chromosomal alterations. Chromosome variability affects human health and natural evolution. Despite the significance of such mutations, no mechanisms explaining the emergence of such translocations have yet been demonstrated. Several models have explored possible changes in interphase nuclei. Evidence for non-homologous chromosomes end joining in meiosis is scarce, and is often limited to uncovering mechanisms in damaged cells only. This study presents a primarily qualitative analysis of contacts of non-homologous chromosomes by short arms, during meiotic prophase I in the mole vole, Ellobius alaicus, a species with a variable karyotype, due to Robertsonian translocations. Immunocytochemical staining of spermatocytes demonstrated the presence of four contact types for non-homologous chromosomes in meiotic prophase I: (1) proximity, (2) touching, (3) anchoring/tethering, and (4) fusion. Our results suggest distinct mechanisms for chromosomal interactions in meiosis. Thus, we propose to change the translocation mechanism model from ‘contact first’ to ‘contact first in meiosis’.

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