scholarly journals Telomeres act autonomously in maize to organize the meiotic bouquet from a semipolarized chromosome orientation

2002 ◽  
Vol 157 (2) ◽  
pp. 231-242 ◽  
Author(s):  
Peter M. Carlton ◽  
W. Zacheus Cande
Keyword(s):  
Large Scale ◽  
Nuclear Periphery ◽  
Small Region ◽  
Homologous Chromosomes ◽  
Cis Acting ◽  
Chromosome Architecture ◽  
Meiotic Chromosomes ◽  
Ring Chromosomes ◽  
Bouquet Stage ◽  
Chromosome Regions

During meiosis, chromosomes undergo large-scale reorganization to allow pairing between homologues, which is necessary for recombination and segregation. In many organisms, pairing of homologous chromosomes is accompanied, and possibly facilitated, by the bouquet, the clustering of telomeres in a small region of the nuclear periphery. Taking advantage of the cytological accessibility of meiosis in maize, we have characterized the organization of centromeres and telomeres throughout meiotic prophase. Our results demonstrate that meiotic centromeres are polarized prior to the bouquet stage, but that this polarization does not contribute to bouquet formation. By examining telocentric and ring chromosomes, we have tested the cis-acting requirements for participation in the bouquet. We find that: (a) the healed ends of broken chromosomes, which contain telomere repeats, can enter the bouquet; (b) ring chromosomes enter the bouquet, indicating that terminal position on a chromosome is not necessary for telomere sequences to localize to the bouquet; and (c) beginning at zygotene, the behavior of telomeres is dominant over any centromere-mediated chromosome behavior. The results of this study indicate that specific chromosome regions are acted upon to determine the organization of meiotic chromosomes, enabling the bouquet to form despite large-scale changes in chromosome architecture.

scholarly journals Memoirs: The Spermatogenesis of Lepidosiren Paradoxa

1911 ◽  
Vol s2-57 (225) ◽  
pp. 1-44
Author(s):  
W. E. AGAR
Keyword(s):  
Nuclear Membrane ◽  
Early Prophase ◽  
Division Plane ◽  
Homologous Chromosomes ◽  
Meiotic Chromosomes ◽  
Advanced Stages ◽  
Somatic Number ◽  
Bouquet Stage ◽  
Different Parts ◽  
Metaphase I

The different generations of cells composing the germinal epithelium, resemble those often described in other forms, especially in the Amphibia. Very little arrangement of the different generations in different parts of the testis could be observed. The somatic number of chromosomes is thirty-eight. One pair of these is conspicuously larger than the rest. The reduced number of chromosomes in the bouquet stage appears to be arrived at by a parallel conjugation in the early prophase according to von Winiwarter's scheme. In strepsinema, which synchronises with the onset of synizesis, the conjugants separate except at their ends, to form very long-drawn-out rings. During synizesis and diakinesis the rings break into their constituents, and the somatic number of univalent chromosomes is again obtained, the "homologous" chromosomes being often widely separated from each other. During diakinesis each univalent becomes divided by a transverse constriction, which probably corresponds with the apices of the V's of the pre-meiotic chromosomes, and also with the transverse division of the Copepod type of tetrad, which cannot therefore be taken as indicating the point of junction of two chromosomes united end to end, As in Copepods, the transverse constriction is not the division plane in either mitosis, but disappears during anaphase II. After the dissolution of the nuclear membrane "homologous" chromosomes are seen to approach each other, and join together a second time to form the rings or modifications of them found in metaphase I. The first maturation division separates entire "homologous" chromosomes. There is no resting stage between the two divisions. In the second division the chromosomes divide longitudinally, forming "tetrads," etc., very like those of metaphase I. A resting or semi-resting stage may be intercalated into the spermatocyte diakinesis. In this condition the chromosomes, in the somatic number, are distributed round the periphery of the nucleus just under the nuclear membrane. In advanced stages they lose their regular shapes and become connected by numerous anastomoses. In one testis several spermatocytes in this stage have taken on all the characters of oocytes. The spermatogonial prophases are of a very simple nature, and show no sign of anything comparable to the stage of zygonerna. In the spermatogonial and also in the somatic nuclei the chromosomes are arranged in a definite plan, the smaller and larger ones being grouped together. Within the main groups there is also evidence of a tendency for chromosomes of equal size to be next to each other.

scholarly journals Molecular organization of mammalian meiotic chromosome axis revealed by expansion STORM microscopy

2019 ◽  
Vol 116 (37) ◽  
pp. 18423-18428 ◽  
Author(s):  
Huizhong Xu ◽  
Zhisong Tong ◽  
Qing Ye ◽  
Tengqian Sun ◽  
Zhenmin Hong ◽  
...  
Keyword(s):  
Meiotic Chromosome ◽  
Molecular Organization ◽  
Homologous Chromosomes ◽  
Meiotic Chromosomes ◽  
C Terminus ◽  
Stochastic Optical Reconstruction Microscopy ◽  
Optical Reconstruction ◽  
20 Nm ◽  
Chromosome Axis

During prophase I of meiosis, chromosomes become organized as loop arrays around the proteinaceous chromosome axis. As homologous chromosomes physically pair and recombine, the chromosome axis is integrated into the tripartite synaptonemal complex (SC) as this structure’s lateral elements (LEs). While the components of the mammalian chromosome axis/LE—including meiosis-specific cohesin complexes, the axial element proteins SYCP3 and SYCP2, and the HORMA domain proteins HORMAD1 and HORMAD2—are known, the molecular organization of these components within the axis is poorly understood. Here, using expansion microscopy coupled with 2-color stochastic optical reconstruction microscopy (STORM) imaging (ExSTORM), we address these issues in mouse spermatocytes at a resolution of 10 to 20 nm. Our data show that SYCP3 and the SYCP2 C terminus, which are known to form filaments in vitro, form a compact core around which cohesin complexes, HORMADs, and the N terminus of SYCP2 are arrayed. Overall, our study provides a detailed structural view of the meiotic chromosome axis, a key organizational and regulatory component of meiotic chromosomes.

scholarly journals Synaptonemal Complex dimerization regulates chromosome alignment and crossover patterning in meiosis

2020 ◽  
Author(s):  
Spencer G. Gordon ◽  
Lisa E. Kursel ◽  
Kewei Xu ◽  
Ofer Rog
Keyword(s):  
Synaptonemal Complex ◽  
Sequence Homology ◽  
Genetic Information ◽  
Large Scale ◽  
Molecular Mechanisms ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Local Sequence ◽  
Chromosome Alignment ◽  
Dimerization Interface

AbstractDuring sexual reproduction the parental homologous chromosomes find each other (pair) and align along their lengths by integrating local sequence homology with large-scale contiguity, thereby allowing for precise exchange of genetic information. The Synaptonemal Complex (SC) is a conserved zipper-like structure that assembles between the homologous chromosomes. This phase-separated interface brings chromosomes together and regulates exchanges between them. However, the molecular mechanisms by which the SC carries out these functions remain poorly understood. Here we isolated and characterized two mutations in the dimerization interface in the middle of the SC zipper in C. elegans. The mutations perturb both chromosome alignment and the regulation of genetic exchanges. Underlying the chromosome-scale phenotypes are distinct alterations to the way SC subunits interact with one another. We propose that the SC brings homologous chromosomes together through two biophysical activities: obligate dimerization that prevents assembly on unpaired chromosomes; and a tendency to phase-separate that extends pairing interactions along the entire length of the chromosomes.

scholarly journals A molecular model for the role of SYCP3 in meiotic chromosome organisation

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Johanna Liinamaria Syrjänen ◽  
Luca Pellegrini ◽  
Owen Richard Davies
Keyword(s):  
Molecular Model ◽  
Meiotic Chromosome ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Meiotic Chromosomes ◽  
Double Stranded Dna ◽  
Evolutionarily Conserved ◽  
20 Nm ◽  
Chromosome Organisation

The synaptonemal complex (SC) is an evolutionarily-conserved protein assembly that holds together homologous chromosomes during prophase of the first meiotic division. Whilst essential for meiosis and fertility, the molecular structure of the SC has proved resistant to elucidation. The SC protein SYCP3 has a crucial but poorly understood role in establishing the architecture of the meiotic chromosome. Here we show that human SYCP3 forms a highly-elongated helical tetramer of 20 nm length. N-terminal sequences extending from each end of the rod-like structure bind double-stranded DNA, enabling SYCP3 to link distant sites along the sister chromatid. We further find that SYCP3 self-assembles into regular filamentous structures that resemble the known morphology of the SC lateral element. Together, our data form the basis for a model in which SYCP3 binding and assembly on meiotic chromosomes leads to their organisation into compact structures compatible with recombination and crossover formation.

scholarly journals One-dimensional spatial patterning along mitotic chromosomes: A mechanical basis for macroscopic morphogenesis

2020 ◽  
Vol 117 (43) ◽  
pp. 26749-26755
Author(s):  
Lingluo Chu ◽  
Zhangyi Liang ◽  
Maria V. Mukhina ◽  
Jay K. Fisher ◽  
John W. Hutchinson ◽  
...  
Keyword(s):  
Spatial Patterning ◽  
Geometric Form ◽  
Mitotic Chromosomes ◽  
Homologous Chromosomes ◽  
One Dimensional ◽  
Meiotic Chromosomes ◽  
Planar Arrays ◽  
Mechanical Basis ◽  
Continuous Presence ◽  
Morphological Patterns

Spatial patterns are ubiquitous in both physical and biological systems. We have recently discovered that mitotic chromosomes sequentially acquire two interesting morphological patterns along their structural axes [L. Chu et al., Mol. Cell, 10.1016/j.molcel.2020.07.002 (2020)]. First, axes of closely conjoined sister chromosomes acquire regular undulations comprising nearly planar arrays of sequential half-helices of similar size and alternating handedness, accompanied by periodic kinks. This pattern, which persists through all later stages, provides a case of the geometric form known as a “perversion.” Next, as sister chromosomes become distinct parallel units, their individual axes become linked by bridges, which are themselves miniature axes. These bridges are dramatically evenly spaced. Together, these effects comprise a unique instance of spatial patterning in a subcellular biological system. We present evidence that axis undulations and bridge arrays arise by a single continuous mechanically promoted progression, driven by stress within the chromosome axes. We further suggest that, after sister individualization, this same stress also promotes chromosome compaction by rendering the axes susceptible to the requisite molecular remodeling. Thus, by this scenario, the continuous presence of mechanical stress within the chromosome axes could potentially underlie the entire morphogenetic chromosomal program. Direct analogies with meiotic chromosomes suggest that the same effects could underlie interactions between homologous chromosomes as required for gametogenesis. Possible mechanical bases for generation of axis stress and resultant deformations are discussed. Together, these findings provide a perspective on the macroscopic changes of organized chromosomes.

scholarly journals Preparation of Hydrophobic Film by Electrospinning for Rapid SERS Detection of Trace Triazophos

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4120
Author(s):  
Fei Shao ◽  
Jiaying Cao ◽  
Ye Ying ◽  
Ying Liu ◽  
Dan Wang ◽  
...  
Keyword(s):  
Hot Spots ◽  
Large Scale ◽  
Limit Of Detection ◽  
Small Region ◽  
Sers Substrate ◽  
Ag Nps ◽  
Electrospinning Technique ◽  
Heterocyclic Molecules ◽  
Surface Enhanced Raman ◽  
Sers Detection

For real application, it is an urgent demand to fabricate stable and flexible surface-enhanced Raman scattering (SERS) substrates with high enhancement factors in a large-scale and facile way. Herein, by using the electrospinning technique, a hydrophobic and flexible poly(styrene-co-butadiene) (SB) fibrous membrane is obtained, which is beneficial for modification of silver nanoparticles (Ag NPs) colloid in a small region and then formation of more “hot spots” by drying; the final SERS substrate is designated as Ag/SB. Hydrophobic Ag/SB can efficiently capture heterocyclic molecules into the vicinity of hot spots of Ag NPs. Such Ag/SB films are used to quantitatively detect trace triazophos residue on fruit peels or in the juice, and the limit of detection (LOD) of 2.5 × 10−8 M is achieved. Ag/SB films possess a capability to resist heat. As a case, 6-mercaptopurine (6MP) that just barely dissolves in 90 °C water is picked for conducting Ag/SB-film-based experiments.

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 Chromosomal G-dark Bands Determine the Spatial Organization of Centromeric Heterochromatin in the Nucleus

2001 ◽  
Vol 12 (11) ◽  
pp. 3563-3572 ◽  
Author(s):  
Célia Carvalho ◽  
Henrique M. Pereira ◽  
João Ferreira ◽  
Cristina Pina ◽  
Denise Mendonça ◽  
...  
Keyword(s):  
Satellite Dna ◽  
Spatial Organization ◽  
Nuclear Periphery ◽  
Three Dimensional ◽  
Lymphoid Cells ◽  
Spatial Proximity ◽  
Centromeric Heterochromatin ◽  
Chromosome 11 ◽  
Cis Acting ◽  
Tight Correlation

Gene expression can be silenced by proximity to heterochromatin blocks containing centromeric α-satellite DNA. This has been shown experimentally through cis-acting chromosome rearrangements resulting in linear genomic proximity, or throughtrans-acting changes resulting in intranuclear spatial proximity. Although it has long been been established that centromeres are nonrandomly distributed during interphase, little is known of what determines the three-dimensional organization of these silencing domains in the nucleus. Here, we propose a model that predicts the intranuclear positioning of centromeric heterochromatin for each individual chromosome. With the use of fluorescence in situ hybridization and confocal microscopy, we show that the distribution of centromeric α-satellite DNA in human lymphoid cells synchronized at G0/G1is unique for most individual chromosomes. Regression analysis reveals a tight correlation between nuclear distribution of centromeric α-satellite DNA and the presence of G-dark bands in the corresponding chromosome. Centromeres surrounded by G-dark bands are preferentially located at the nuclear periphery, whereas centromeres of chromosomes with a lower content of G-dark bands tend to be localized at the nucleolus. Consistent with the model, a t(11; 14) translocation that removes G-dark bands from chromosome 11 causes a repositioning of the centromere, which becomes less frequently localized at the nuclear periphery and more frequently associated with the nucleolus. The data suggest that “chromosomal environment” plays a key role in the intranuclear organization of centromeric heterochromatin. Our model further predicts that facultative heterochromatinization of distinct genomic regions may contribute to cell-type specific patterns of centromere localization.

scholarly journals Localization of RAP1 and topoisomerase II in nuclei and meiotic chromosomes of yeast

1992 ◽  
Vol 117 (5) ◽  
pp. 935-948 ◽  
Author(s):  
F Klein ◽  
T Laroche ◽  
ME Cardenas ◽  
JF Hofmann ◽  
D Schweizer ◽  
...  
Keyword(s):  
Topoisomerase Ii ◽  
Meiotic Chromosome ◽  
Nuclear Periphery ◽  
Yeast Cells ◽  
Activator Protein 1 ◽  
Interphase Nuclei ◽  
Telomeric Sequences ◽  
Meiotic Chromosomes ◽  
Punctate Staining

Topoisomerase II (topoII) and RAP1 (Repressor Activator Protein 1) are two abundant nuclear proteins with proposed structural roles in the higher-order organization of chromosomes. Both proteins co-fractionate as components of nuclear scaffolds from vegetatively growing yeast cells, and both proteins are present as components of pachytene chromosome, co-fractionating with an insoluble subfraction of meiotic nuclei. Immunolocalization using antibodies specific for topoII shows staining of an axial core of the yeast meiotic chromosome, extending the length of the synaptonemal complex. RAP1, on the other hand, is located at the ends of the paired bivalent chromosomes, consistent with its ability to bind telomeric sequences in vitro. In interphase nuclei, again in contrast to anti-topoII, anti-RAP1 gives a distinctly punctate staining that is located primarily at the nuclear periphery. Approximately 16 brightly staining foci can be identified in a diploid nucleus stained with anti-RAP1 antibodies, suggesting that telomeres are grouped together, perhaps through interaction with the nuclear envelope.

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