scholarly journals Homologous locus pairing is a transient, diffusion-mediated process in meiotic prophase

2021 ◽  
Author(s):  
Trent A. C. Newman ◽  
Bruno Beltran ◽  
James M. McGehee ◽  
Daniel Elnatan ◽  
Cori K. Cahoon ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Single Cell ◽  
Chromosome Pairing ◽  
Polymer Physics ◽  
Cell Behavior ◽  
Dependent Manner ◽  
Single Linkage ◽  
Fluorescent Reporter ◽  
Homologous Chromosomes ◽  
Prophase I

AbstractThe pairing of homologous chromosomes in meiosis I is essential for sexual reproduction and is mediated, in part, by the formation and repair of Spo11-induced DNA double strand breaks (DSBs). In budding yeast, each cell receives ~150-200 DSBs, yet only a fraction go on to form crossover products. How and why the cell initially co-ordinates so many interactions along each chromosome is not well understood. Using a fluorescent reporter-operator system (FROS), we measure the kinetics of interacting homologous loci at various stages of meiosis. We find that while tagged loci undergo considerable motion throughout prophase I, they are constrained in how far they can diffuse from their homolog pair. This effective tethering radius decreases over the course of meiosis in a DSB-dependent manner. We develop a theoretical model that captures the biological contributions of centromere attachment to the nuclear envelope, homolog pairing, and nuclear confinement. With this model, we demonstrate that the experimentally observed heterogeneity in single-cell behavior and the effective tethering between loci is captured for two polymers forming randomly-spaced linkages. The small number of connections required to reproduce our data demonstrates that a single linkage site between homologous chromosomes can constrain the movement of loci up to hundreds of kilobases away.Significance StatementMeiosis is essential for sexual reproduction, and homologous chromosome pairing is a critical step in this process that must be reliably achieved. We measure the dynamics of homologous loci throughout prophase I of meiosis, demonstrating the transient nature of homolog contacts and heterogeneity in single-cell behavior. We develop a minimal model containing only the basic polymer physics of DNA but is sufficient to reproduce the observed behavior. We show that it only takes a handful of homologous linkages per chromosome to facilitate pairing, demonstrating that a single tethered locus can drastically restrict the diffusion of DNA tens to hundreds of kilobases away. These results demonstrate the central role of random diffusion and polymer physics in facilitating chromosome pairing in meiosis.

scholarly journals The external mechanics of the chromosomes III-Meiosis in triploids

1936 ◽  
Vol 121 (823) ◽  
pp. 290-300 ◽  
Keyword(s):  
Sexual Reproduction ◽  
Chromosome Pairing ◽  
Natural Experiment ◽  
Diploid Species ◽  
Homologous Chromosomes ◽  
Normal Series ◽  
Mitosis And Meiosis ◽  
Meiosis I ◽  
Prophase Of Meiosis ◽  
The Way

Triploid organisms have three homologous chromosomes of each kind instead of the two of diploids. The regular mechanism of heredity fails in these circumstances. The triploid is incapable of breeding true by sexual reproduction. But the way in which it carries out the process of chromosome pairing and segregation is of great significance. The processes take place in normal series, but the relationships they establish are abnormal. A triploid thus provides a natural experiment, with the diploid of its own species as a control for one variable, and with triploids of different species as controls for others. In Tulipa and Hyacinthus I have made use of this experiment for inducing the principles of the external mechanics of chromosomes during the prophase of meiosis. I have inferred from them the relationships between the forces working in mitosis and meiosis. The triploid forms of various Fritillaria species make it possible to test the principles of metaphase mechanics induced from observations on structural hybrids and other polyploids (Darlington, 1932, b , and 1933, c ) as well as from the exceptional behaviour in the diploid species of Fritillaria already discussed.

scholarly journals PAIR3, an axis-associated protein, is essential for the recruitment of recombination elements onto meiotic chromosomes in rice

2011 ◽  
Vol 22 (1) ◽  
pp. 12-19 ◽  
Author(s):  
Kejian Wang ◽  
Mo Wang ◽  
Ding Tang ◽  
Yi Shen ◽  
Baoxiang Qin ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Central Element ◽  
Dependent Manner ◽  
Homologous Pairing ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Meiotic Chromosomes

During meiosis, the paired homologous chromosomes are tightly held together by the synaptonemal complex (SC). This complex consists of two parallel axial/lateral elements (AEs/LEs) and one central element. Here, we observed that PAIR3 localized to the chromosome core during prophase I and associated with both unsynapsed AEs and synapsed LEs. Analyses of the severe pair3 mutant demonstrated that PAIR3 was essential for bouquet formation, homologous pairing and normal recombination, and SC assembly. In addition, we showed that although PAIR3 was not required for the initial recruitment of PAIR2, it was required for the proper association of PAIR2 with chromosomes. Dual immunostaining revealed that PAIR3 highly colocalized with REC8. Moreover, studies using a rec8 mutant indicated that PAIR3 localized to chromosomes in a REC8-dependent manner.

Chromosome pairing in the allotetraploid Aegilops biuncialis and a triploid intergeneric hybrid

Genome ◽  
1996 ◽  
Vol 39 (4) ◽  
pp. 664-670 ◽  
Author(s):  
N. Cuñado ◽  
S. Callejas ◽  
M. J. García ◽  
J. L Santos ◽  
A. Fernández
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Complex Analysis ◽  
Intergeneric Hybrid ◽  
Chiasma Formation ◽  
Triploid Hybrid ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Surface Spread ◽  
Metaphase I

Chromosome pairing behaviour of the natural allotetraploid Aegilops biuncialis (genome UUMM) and a triploid hybrid Ae. biuncialis × Secale cereale (genome UMR) was analyzed by electron microscopy in surface-spread prophase I nuclei. Synaptonemal-complex analysis at zygotene and pachytene revealed that synapsis in the allotetraploid was mostly between homologous chromosomes, although a few quadrivalents were also formed. Only homologous bivalents were observed at metaphase I. In contrast, homoeologous and heterologous chromosome associations were common at prophase I and metaphase I of the triploid hybrid. It is concluded that the mechanism controlling bivalent formation in Ae. biuncialis acts mainly at zygotene by restricting pairing to homologous chromosomes, but also acts at pachytene by preventing chiasma formation in the homoeologous associations. In the hybrid the mechanism fails at both stages. Key words : Aegilops biuncialis, allotetraploid, intergeneric hybrid, pairing control, synaptonemal complex.

Inferences from genetical evidence on the course of meiotic chromosome pairing in plants

1977 ◽  
Vol 277 (955) ◽  
pp. 313-326 ◽  
Keyword(s):  
Chromosome Pairing ◽  
Developmental Stages ◽  
Meiotic Chromosome ◽  
Critical Assessment ◽  
Gene Control ◽  
Meiotic Pairing ◽  
Homologous Chromosomes ◽  
Meiotic Chromosome Pairing ◽  
Combined Use ◽  
Or Gene

Meiotic chromosome pairing is a process that is amenable to genetic and experimental analysis. The combined use of these two approaches allows for the process to be dissected into several finite periods of time in which the developmental stages of pairing can be precisely located. Evidence is now available, in particular in plants, that shows that the pairing of homologous chromosomes, as observed at metaphase I, is affected by events occurring as early as the last premeiotic mitosis; and that the maintenance of this early determined state is subsequently maintained by constituents (presumably proteins) that are sensitive to either colchicine, temperature or gene control. A critical assessment of this evidence in wheat and a comparison of the process of pairing in wheat with the course of meiotic pairing in other plants and animals is presented.

scholarly journals Collective and single cell behavior in epithelial contact inhibition

2012 ◽  
Vol 109 (3) ◽  
pp. 739-744 ◽  
Author(s):  
A. Puliafito ◽  
L. Hufnagel ◽  
P. Neveu ◽  
S. Streichan ◽  
A. Sigal ◽  
...  
Keyword(s):  
Single Cell ◽  
Contact Inhibition ◽  
Cell Behavior

scholarly journals Synaptonemal complex antigen location and conservation.

1987 ◽  
Vol 105 (1) ◽  
pp. 93-103 ◽  
Author(s):  
P B Moens ◽  
C Heyting ◽  
A J Dietrich ◽  
W van Raamsdonk ◽  
Q Chen
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Structural Integrity ◽  
Genetic Recombination ◽  
Positive Control ◽  
Western Blots ◽  
Lateral Element ◽  
Homologous Chromosomes ◽  
Recombination Nodules ◽  
Grain Distribution

The axial cores of chromosomes in the meiotic prophase nuclei of most sexually reproducing organisms play a pivotal role in the arrangement of chromatin, in the synapsis of homologous chromosomes, in the process of genetic recombination, and in the disjunction of chromosomes. We report an immunogold analysis of the axial cores and the synaptonemal complexes (SC) using two mouse monoclonal antibodies raised against isolated rat SCs. In Western blots of purified SCs, antibody II52F10 recognizes a 30- and a 33-kD peptide (Heyting, C., P. B. Moens, W. van Raamsdonk, A. J. J. Dietrich, A. C. G. Vink, and E. J. W. Redeker, 1987, Eur. J. Cell Biol., 43: 148-154). In spreads of rat spermatocyte nuclei it produces gold grains over the cores of autosomal and sex chromosomes. The cores label lightly during the chromosome pairing stage (zygotene) of early meiotic prophase and they become more intensely labeled when they are parallel aligned as the lateral elements of the SC during pachytene (55 grains/micron SC). Statistical analysis of electronically recorded gold grain positions shows that the two means of the bimodal gold grain distribution coincide with the centers of the lateral elements. At diplotene, when the cores separate, the antigen is still detected along the length of the core and the enlarged ends are heavily labeled. Shadow-cast SC preparations show that recombination nodules are not labeled. The continued presence suggests that the antigens serve a continuing function in the cores, such as chromatin binding, and/or structural integrity. Antibody III15B8, which does not recognize the 30- and 33-kD peptides, produces gold grains predominantly between the lateral elements. The grain distribution is bimodal with the mean of each peak just inside the pairing face of the lateral element. The antigen is present where and while the cores of the homologous chromosomes are paired. From the location and the timing, it is assumed that the antigen recognized by III15B8 functions in chromosome pairing at meiotic prophase. The two anti-rat SC antibodies label rat and mouse SCs but not rabbit or dog SCs. A positive control using human CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) anti-centromere serum gives equivalent labeling of SC centromeres in the rat, mouse, rabbit, and dog. It is concluded that the SC antigens recognized by II52F10 and III15B8 are not widely conserved. The two antibodies do not bind to cellular or nuclear components of somatic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals More than efficacy revealed by single-cell analysis of antiviral therapeutics

2019 ◽  
Vol 5 (10) ◽  
pp. eaax4761 ◽  
Author(s):  
Wu Liu ◽  
Mehmet U. Caglar ◽  
Zhangming Mao ◽  
Andrew Woodman ◽  
Jamie J. Arnold ◽  
...  
Keyword(s):  
Viral Infection ◽  
Single Cell ◽  
Single Cell Analysis ◽  
Principal Component ◽  
Cell Analysis ◽  
Infection Cycle ◽  
Reporter Protein ◽  
Fluorescent Reporter ◽  
Infection Dynamics ◽  
Infected Cells

Because many aspects of viral infection dynamics and inhibition are governed by stochastic processes, single-cell analysis should provide more information than approaches using population averaging. We have developed a microfluidic device composed of ~6000 wells, with each well containing a microstructure to capture single, infected cells replicating an enterovirus expressing a fluorescent reporter protein. We have used this system to characterize enterovirus inhibitors with distinct mechanisms of action. Single-cell analysis reveals that each class of inhibitor interferes with the viral infection cycle in a manner that can be distinguished by principal component analysis. Single-cell analysis of antiviral candidates not only reveals efficacy but also facilitates clustering of drugs with the same mechanism of action and provides some indication of the ease with which resistance will develop.

scholarly journals Piquiá Shells (Caryocar villosum): A Fruit by-Product with Antioxidant and Antiaging Properties in Caenorhabditis elegans

2020 ◽  
Vol 2020 ◽  
pp. 1-19 ◽  
Author(s):  
Mariana Roxo ◽  
Herbenya Peixoto ◽  
Pille Wetterauer ◽  
Emerson Lima ◽  
Michael Wink
Keyword(s):  
Caenorhabditis Elegans ◽  
Lethal Dose ◽  
Pcr Analysis ◽  
Transcriptional Level ◽  
Dependent Manner ◽  
Wild Type ◽  
Fluorescent Reporter ◽  
Triterpenoid Saponins ◽  
Promising Source

In a context of rising demand for sustainable antiaging interventions, fruit processing by-products are a promising source of bioactive compounds for the production of antiaging dietary supplements. Piquiá (Caryocar villosum) is a native Amazonian fruit consisting of 65% nonedible shells. In the present study, the phytochemical profile of a hydroalcoholic extract of piquiá shells (CV) was characterized by LC-MS/MS analysis. Its antioxidant and antiaging activities were investigated using the nematode Caenorhabditis elegans as an in vivo model. CV is mainly composed by hydrolysable tannins and triterpenoid saponins. The extract enhanced stress resistance of wild-type and mutant worms by reducing the intracellular levels of reactive oxygen species (ROS) and by increasing their survival against a lethal dose of the prooxidant juglone. These effects involved the upregulation of sod-3 and downregulation of gst-4 and hsp-16.2, studied through the GFP fluorescent reporter intensity and at the transcriptional level by qRT-PCR analysis. CV extended the lifespan of wild-type worms in a DAF-16/FoxO- and SKN-1/Nrf-dependent manner. Taken together, our findings indicate piquiá shells as potential candidates for nutraceutical applications. Further studies are needed to validate the relevance of our findings to antiaging interventions in humans.

scholarly journals Statins Perturb Gβγ Signaling and Cell Behavior in a Gγ Subtype Dependent Manner

2019 ◽  
Vol 95 (4) ◽  
pp. 361-375 ◽  
Author(s):  
Mithila Tennakoon ◽  
Dinesh Kankanamge ◽  
Kanishka Senarath ◽  
Zehra Fasih ◽  
Ajith Karunarathne
Keyword(s):  
Cell Behavior ◽  
Dependent Manner
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