scholarly journals Architecture of the Nuclear Periphery of Rat Pachytene Spermatocytes: Distribution of Nuclear Envelope Proteins in Relation to Synaptonemal Complex Attachment Sites

1999 ◽  
Vol 10 (4) ◽  
pp. 1235-1245 ◽  
Author(s):  
Manfred Alsheimer ◽  
Elisabeth von Glasenapp ◽  
Robert Hock ◽  
Ricardo Benavente
Keyword(s):  
Nuclear Envelope ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Nuclear Periphery ◽  
Cell Fractionation ◽  
Nuclear Interior ◽  
Meiotic Chromosomes ◽  
Attachment Sites ◽  
Form Part ◽  
Pachytene Spermatocytes

The nucleus of spermatocytes provides during the first meiotic prophase an interesting model for investigating relationships of the nuclear envelope (NE) with components of the nuclear interior. During the pachytene stage, meiotic chromosomes are synapsed via synaptonemal complexes (SCs) and attached through both ends to the nuclear periphery. This association is dynamic because chromosomes move during the process of synapsis and desynapsis that takes place during meiotic prophase. The NE of spermatocytes possesses some peculiarities (e.g., lower stability than in somatic cells, expression of short meiosis-specific lamin isoforms called C2 and B3) that could be critically involved in this process. For better understanding of the association of chromosomes with the nuclear periphery, in the present study we have investigated the distribution of NE proteins in relation to SC attachment sites. A major outcome was the finding that lamin C2 is distributed in the form of discontinuous domains at the NE of spermatocytes and that SC attachment sites are embedded in these domains. Lamin C2 appears to form part of larger structures as suggested by cell fractionation experiments. According to these results, we propose that the C2-containing domains represent local reinforcements of the NE that are involved in the proper attachment of SCs.

scholarly journals Heterologous synapsis in C. elegans is regulated by meiotic double-strand breaks and crossovers

2021 ◽  
Author(s):  
Hanwenheng Liu ◽  
Spencer G. Gordon ◽  
Ofer Rog
Keyword(s):  
Nuclear Envelope ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Double Strand Breaks ◽  
Strand Breaks ◽  
C Elegans ◽  
Homologous Sequences ◽  
Almost All ◽  
Break Formation ◽  
Successful Production

AbstractAlignment of the parental chromosomes during meiotic prophase is key to the formation of genetic exchanges, or crossovers, and consequently to the successful production of gametes. In almost all studied organisms, alignment involves synapsis: the assembly of a conserved inter-chromosomal interface called the synaptonemal complex (SC). While the SC usually synapses homologous sequences, it can assemble between heterologous sequences. However, little is known about the regulation of heterologous synapsis. Here we study the dynamics of heterologous synapsis in the nematode C. elegans. We characterize two experimental scenarios: SC assembly onto a folded-back chromosome that cannot pair with its homologous partner; and synapsis of pseudo-homologs, a fusion chromosome partnering with an unfused chromosome half its size. We observed elevated levels of heterologous synapsis when the number of meiotic double-strand breaks or crossovers were reduced, indicating that the promiscuity of synapsis is regulated by break formation or repair. By manipulating the levels of breaks and crossovers, we infer both chromosome-specific and nucleus-wide regulation on heterologous synapsis. Finally, we identify differences between the two conditions, suggesting that attachment to the nuclear envelope plays a role in regulating heterologous synapsis.

scholarly journals Mad1’s ability to interact with Mad2 is essential to regulate and monitor meiotic synapsis in C. elegans

2021 ◽  
Author(s):  
Alice Devigne ◽  
Needhi Bhalla
Keyword(s):  
Nuclear Envelope ◽  
Meiotic Prophase ◽  
Nuclear Periphery ◽  
Spindle Checkpoint ◽  
Primary Role ◽  
Cis Acting ◽  
C Elegans ◽  
Meiotic Synapsis ◽  
Segregation Of Chromosomes

Meiotic homolog synapsis is essential to ensure accurate segregation of chromosomes during meiosis.  In C. elegans , synapsis and a checkpoint that monitors synapsis relies on the spindle checkpoint components, Mad1 and Mad2, and Pairing Centers (PCs), cis-acting loci that interact with the nuclear envelope to mobilize chromosomes within the nucleus. Here, we show that mutations in some spindle checkpoint mutants affect PC movement early in meiotic prophase, consistent with a link between PC mobility and the regulation of synapsis. Further, we test what specific functions of Mad1 and Mad2 are required to regulate and monitor synapsis. We find that a mutation that abrogates Mad1’s localization to the nuclear periphery abolishes the synapsis checkpoint but has no effect on Mad2’s localization to the nuclear periphery or synapsis. By contrast, a mutation that prevents Mad1’s interaction with Mad2 abolishes the synapsis checkpoint, delays synapsis and fails to localize Mad2 to the nuclear periphery. These data indicate that Mad1’s primary role in regulating synapsis is through control of Mad2 and that Mad2 can bind other factors at the nuclear periphery. We also tested whether Mad2’s ability to adopt a specific conformation associated with its activity during spindle checkpoint function is required for its role in meiosis. A mutation that prevents Mad2 from adopting its active conformer fails to localize to the nuclear periphery, abolishes the synapsis checkpoint and exhibits substantial defects in meiotic synapsis. Thus, Mad2, and its regulation by Mad1, is a major regulator of meiotic synapsis in C. elegans .

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.

scholarly journals FBXO47 regulates telomere-inner nuclear envelope integration by stabilizing TRF2 during meiosis

2019 ◽  
Author(s):  
Rong Hua ◽  
Huafang Wei ◽  
Chao Liu ◽  
Yue Zhang ◽  
Siyu Liu ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Shelterin Complex ◽  
Meiotic Prophase I ◽  
F Box Protein ◽  
Bouquet Stage

Abstract During meiosis, telomere attachment to the inner nuclear envelope is required for proper pairing of homologous chromosomes and recombination. Here, we identified F-box protein 47 (FBXO47) as a regulator of the telomeric shelterin complex that is specifically expressed during meiotic prophase I. Knockout of Fbxo47 in mice leads to infertility in males. We found that the Fbxo47 deficient spermatocytes are unable to form a complete synaptonemal complex. FBXO47 interacts with TRF1/2, and the disruption of Fbxo47 destabilizes TRF2, leading to unstable telomere attachment and slow traversing through the bouquet stage. Our findings uncover a novel mechanism of FBXO47 in telomeric shelterin subunit stabilization during meiosis.

Synaptonemal complex karyotyping in Melanoplus differentialis

1977 ◽  
Vol 26 (1) ◽  
pp. 229-250
Author(s):  
A.J. Solari ◽  
S.J. Counce
Keyword(s):  
Nuclear Envelope ◽  
X Chromosome ◽  
Meiotic Prophase ◽  
Polar Region ◽  
Relative Length ◽  
Characteristic Sequence ◽  
Mitotic Chromosomes ◽  
Nuclear Interior ◽  
Melanoplus Differentialis ◽  
The Relationship

The chromosomal axes of the spermatocytes of the grasshopper Melanoplus differentialis have been studied with a modification of the microspreading procedure used previously. The whole complement of synaptonemal complexes (SCs) and the axis of the X chromosome have been described and measured. The relative length of each SC is characteristic and constant and permits the construction of an idiogram. Relative lengths of SCs are almost equal to the relative lengths of mitotic chromosomes of spermatogonia (with the exception of the X chromosome), thus extending to an invertebrate the relationship between SCs and mitotic chromosomes that has been demonstrated in mammals. All the SCs except the 3 smallest (which are apparently telocentric) show a small short arm beyond the kinetochore. The progression of changes in the chromosomal axes during meiotic prophase has been staged by centriolar behaviour. During leptotene, axes are first formed near the nuclear envelope at a special (polar) region. SCs also begin to appear in the polar region and extend towards the nuclear interior. The beginning and completion of synapsis is not synchronous among bivalents. The X-axis is formed in midzygotene and shows a characteristic sequence of changes in shape during pachytene. Cells in post-synaptic stages show whole chromosome complements with characteristic chiasmatic configurations. Kinetochores are prominent and bipartite during diplotene-diakinesis.

scholarly journals SWR1-independent association of H2A.Z to the LINC complex promotes meiotic chromosome motion

2020 ◽  
Author(s):  
Sara González-Arranz ◽  
Jennifer M. Gardner ◽  
Zulin Yu ◽  
Neem J. Patel ◽  
Jonna Heldrich ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Meiotic Prophase ◽  
Meiotic Chromosome ◽  
Nuclear Periphery ◽  
The Sun ◽  
Chromosome Movement ◽  
Linc Complex ◽  
Associated Factor ◽  
Independent Association ◽  
Chromosome Motion

ABSTRACTThe H2A.Z histone variant is deposited into chromatin by the SWR1 complex affecting multiple aspects of meiosis. Here we describe a SWR1-independent localization of H2A.Z at meiotic telomeres and the centrosome. We demonstrate that H2A.Z colocalizes and interacts with Mps3, the SUN component of the LINC complex that spans the nuclear envelope and links meiotic telomeres to the cytoskeleton promoting meiotic chromosome movement. H2A.Z also interacts with the meiosis-specific Ndj1 protein that anchors telomeres to the nuclear periphery via Mps3. Telomeric localization of H2A.Z depends on Ndj1 and the N-terminal domain of Mps3. Although telomeric attachment to the nuclear envelope is maintained in the absence of H2A.Z, the distribution of Mps3 is altered. The velocity of chromosome movement during meiotic prophase I is reduced in the htz1Δ mutant lacking H2A.Z, but it is unaffected in swr1Δ cells. We reveal that H2A.Z is an additional LINC-associated factor that contributes to promote telomere-driven chromosome motion critical for error-free gametogenesis.

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 The CSN/COP9 Signalosome Regulates Synaptonemal Complex Assembly during Meiotic Prophase I of Caenorhabditis elegans

PLoS Genetics ◽  
2014 ◽  
Vol 10 (11) ◽  
pp. e1004757 ◽  
Author(s):  
Heather Brockway ◽  
Nathan Balukoff ◽  
Martha Dean ◽  
Benjamin Alleva ◽  
Sarit Smolikove
Keyword(s):  
Caenorhabditis Elegans ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Cop9 Signalosome ◽  
Complex Assembly ◽  
Prophase I ◽  
Meiotic Prophase I
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