Chromosome Structure and Homologous Chromosome Association During Meiotic Prophase in Caenorhabditis elegans

2011 ◽  
pp. 549-562 ◽  
Author(s):  
Kentaro Nabeshima
Keyword(s):  
Caenorhabditis Elegans ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Chromosome Structure ◽  
Chromosome Association

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 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

scholarly journals Automated and customizable quantitative image analysis of whole Caenorhabditis elegans germlines

Genetics ◽  
2021 ◽  
Author(s):  
Erik Toraason ◽  
Victoria L Adler ◽  
Nicole A Kurhanewicz ◽  
Acadia DiNardo ◽  
Adam M Saunders ◽  
...  
Keyword(s):  
Image Analysis ◽  
Caenorhabditis Elegans ◽  
Germ Cell ◽  
Meiotic Prophase ◽  
Quantitative Image Analysis ◽  
Dna Breaks ◽  
C Elegans ◽  
Quantitative Image ◽  
Cytological Features ◽  
Single Nucleus

Abstract Arranged in a spatial-temporal gradient for germ cell development, the adult germline of Caenorhabditis elegans is an excellent system for understanding the generation, differentiation, function, and maintenance of germ cells. Imaging whole C. elegans germlines along the distal-proximal axis enables powerful cytological analyses of germ cell nuclei as they progress from the pre-meiotic tip through all the stages of meiotic prophase I. To enable high-content image analysis of whole C. elegans gonads, we developed a custom algorithm and pipelines to function with image processing software that enables: (1) quantification of cytological features at single nucleus resolution from immunofluorescence images; and (2) assessment of these individual nuclei based on their position within the germline. We show the capability of our quantitative image analysis approach by analyzing multiple cytological features of meiotic nuclei in whole C. elegans germlines. First, we quantify double-strand DNA breaks (DSBs) per nucleus by analyzing DNA-associated foci of the recombinase RAD-51 at single-nucleus resolution in the context of whole germline progression. Second, we quantify the DSBs that are licensed for crossover repair by analyzing foci of MSH-5 and COSA-1 when they associate with the synaptonemal complex during meiotic prophase progression. Finally, we quantify P-granule composition across the whole germline by analyzing the colocalization of PGL-1 and ZNFX-1 foci. Our image analysis pipeline is an adaptable and useful method for researchers spanning multiple fields using the C. elegans germline as a model system.

scholarly journals Regulating chromosomal movement by the cochaperone FKB-6 ensures timely pairing and synapsis

2017 ◽  
Vol 216 (2) ◽  
pp. 393-408 ◽  
Author(s):  
Benjamin Alleva ◽  
Nathan Balukoff ◽  
Amy Peiper ◽  
Sarit Smolikove
Keyword(s):  
Nuclear Envelope ◽  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Homologous Chromosome ◽  
Strand Break ◽  
Crossing Over ◽  
Chromosome Movement ◽  
Microtubule Network ◽  
Homologous Chromosome Pairing ◽  
Proper Movement

In meiotic prophase I, homologous chromosome pairing is promoted through chromosome movement mediated by nuclear envelope proteins, microtubules, and dynein. After proper homologue pairing has been established, the synaptonemal complex (SC) assembles along the paired homologues, stabilizing their interaction and allowing for crossing over to occur. Previous studies have shown that perturbing chromosome movement leads to pairing defects and SC polycomplex formation. We show that FKB-6 plays a role in SC assembly and is required for timely pairing and proper double-strand break repair kinetics. FKB-6 localizes outside the nucleus, and in its absence, the microtubule network is altered. FKB-6 is required for proper movement of dynein, increasing resting time between movements. Attenuating chromosomal movement in fkb-6 mutants partially restores the defects in synapsis, in agreement with FKB-6 acting by decreasing chromosomal movement. Therefore, we suggest that FKB-6 plays a role in regulating dynein movement by preventing excess chromosome movement, which is essential for proper SC assembly and homologous chromosome pairing.

scholarly journals A possible effect of B-chromosomes on metaphase I homologous chromosome association in rye

Heredity ◽  
1991 ◽  
Vol 67 (1) ◽  
pp. 123-128 ◽  
Author(s):  
M T Alvarez ◽  
A Fominaya ◽  
M Perez de la Vega
Keyword(s):  
Homologous Chromosome ◽  
B Chromosomes ◽  
Chromosome Association ◽  
Metaphase I

scholarly journals Time-course analysis of early meiotic prophase events informs mechanisms of homolog pairing and synapsis in Caenorhabditis elegans

2017 ◽  
Author(s):  
Susanna Mlynarczyk-Evans ◽  
Anne M Villeneuve
Keyword(s):  
Caenorhabditis Elegans ◽  
Meiotic Prophase ◽  
Time Course ◽  
S Phase ◽  
Resolution Time ◽  
X Chromosomes ◽  
Homologous Chromosomes ◽  
Homolog Pairing ◽  
Nuclear Reorganization ◽  
Active Mobilization

AbstractSegregation of homologous chromosomes during meiosis depends on their ability to reorganize within the nucleus, discriminate among potential partners, and stabilize pairwise associations through assembly of the synaptonemal complex (SC). Here we report a high-resolution time-course analysis of these key early events during Caenorhabditis elegans meiosis. Labeled nucleotides are incorporated specifically into the X chromosomes during the last two hours of S phase, a property we exploit to identify a highly synchronous cohort of nuclei. By tracking X-labeled nuclei through early meiotic prophase, we define the sequence and duration of chromosome movement, nuclear reorganization, pairing at pairing centers (PCs), and SC assembly. Appearance of ZYG-12 foci (marking attachment of PCs to the nuclear envelope) and onset of active mobilization occur within an hour after S phase completion. Movement occurs for nearly 2 hours before stable pairing is observed at PCs, and autosome movement continues for roughly 4 hours thereafter. Chromosomes are tightly clustered during a 2-3 hour post-pairing window, during which the bulk of SC assembly occurs; however, initiation of SC assembly can precede evident chromosome clustering. SC assembly on autosomes begins immediately after PC pairing is detected and is completed within about 3.5 hours. For the X chromosomes, PC pairing is contemporaneous with autosomal pairing, but autosomes complete synapsis earlier (on average) than X chromosomes, implying that X chromosomes have a delay in onset and/or a slower rate of SC assembly. Additional evidence suggests that transient association among chromosomes sharing the same PC protein may contribute to partner discrimination.

scholarly journals Sister chromatid repair maintains genomic integrity during meiosis in Caenorhabditis elegans

2020 ◽  
Author(s):  
Erik Toraason ◽  
Cordell Clark ◽  
Anna Horacek ◽  
Marissa L. Glover ◽  
Alina Salagean ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Sister Chromatid ◽  
Meiotic Prophase ◽  
Genome Integrity ◽  
Early Prophase ◽  
Dna Breaks ◽  
Late Prophase ◽  
Exogenous Dna ◽  
Prophase I ◽  
Meiotic Prophase I

SummaryDuring meiosis, the maintenance of genome integrity is critical for generating viable haploid gametes [1]. In meiotic prophase I, double-strand DNA breaks (DSBs) are induced and a subset of these DSBs are repaired as interhomolog crossovers to ensure proper chromosome segregation. DSBs in excess of the permitted number of crossovers must be repaired by other pathways to ensure genome integrity [2]. To determine if the sister chromatid is engaged for meiotic DSB repair during oogenesis, we developed an assay to detect sister chromatid repair events at a defined DSB site during Caenorhabditis elegans meiosis. Using this assay, we directly demonstrate that the sister chromatid is available as a meiotic repair template for both crossover and noncrossover recombination, with noncrossovers being the predominant recombination outcome. We additionally find that the sister chromatid is the exclusive recombination partner for DSBs during late meiotic prophase I. Analysis of noncrossover conversion tract sequences reveals that DSBs are processed similarly throughout prophase I and recombination intermediates remain central around the DSB site. Further, we demonstrate that the SMC-5/6 complex is required for long conversion tracts in early prophase I and intersister crossovers during late meiotic prophase I; whereas, the XPF-1 nuclease is required only in late prophase to promote sister chromatid repair. In response to exogenous DNA damage at different stages of meiosis, we find that mutants for SMC-5/6 and XPF-1 have differential effects on progeny viability. Overall, we propose that SMC-5/6 both processes recombination intermediates and promotes sister chromatid repair within meiotic prophase I, while XPF-1 is required as an intersister resolvase only in late prophase I.

scholarly journals Exposure to the anthelmintic dinitroaniline oryzalin causes changes in meiotic prophase morphology and loss of synaptonemal complexes in the nematode Caenorhabditis elegans

2021 ◽  
Vol 2 ◽  
Author(s):  
Paul Goldstein
Keyword(s):  
Caenorhabditis Elegans ◽  
Nuclear Matrix ◽  
Meiotic Prophase ◽  
Parasitic Nematodes ◽  
Nematode Caenorhabditis Elegans ◽  
Synaptonemal Complexes ◽  
Prophase I ◽  
Meiotic Prophase I

Abstract The anthelmintic dinitroaniline oryzalin interferes with the formation of microtubules and inhibits meiosis and mitosis in nematodes. Exposure to oryzalin resulted in deterioration in morphology of the oocytes and loss of synaptonemal complexes at meiotic prophase I. The nuclear matrix and envelope were poorly formed, and the central rachis was diminished. These results provide the basis for the loss of fecundity after treatment with the oryzalin resulting in control of parasitic nematodes.

scholarly journals Interdependent and separable functions of Caenorhabditis elegans MRN-C complex members couple formation and repair of meiotic DSBs

2018 ◽  
Vol 115 (19) ◽  
pp. E4443-E4452 ◽  
Author(s):  
Chloe Girard ◽  
Baptiste Roelens ◽  
Karl A. Zawadzki ◽  
Anne M. Villeneuve
Keyword(s):  
Caenorhabditis Elegans ◽  
Meiotic Prophase ◽  
Nijmegen Breakage Syndrome ◽  
Potential Threat ◽  
Dsb Repair ◽  
Ssdna Binding ◽  
Mrn Complex ◽  
Meiotic Dsbs ◽  
Ssdna Binding Protein ◽  
C Complex

Faithful inheritance of genetic information through sexual reproduction relies on the formation of crossovers between homologous chromosomes during meiosis, which, in turn, relies on the formation and repair of numerous double-strand breaks (DSBs). As DSBs pose a potential threat to the genome, mechanisms that ensure timely and error-free DSB repair are crucial for successful meiosis. Here, we identify NBS-1, the Caenorhabditis elegans ortholog of the NBS1 (mutated in Nijmegen Breakage Syndrome) subunit of the conserved MRE11-RAD50-NBS1/Xrs2 (MRN) complex, as a key mediator of DSB repair via homologous recombination (HR) during meiosis. Loss of nbs-1 leads to severely reduced loading of recombinase RAD-51, ssDNA binding protein RPA, and pro-crossover factor COSA-1 during meiotic prophase progression; aggregated and fragmented chromosomes at the end of meiotic prophase; and 100% progeny lethality. These phenotypes reflect a role for NBS-1 in processing of meiotic DSBs for HR that is shared with its interacting partners MRE-11-RAD-50 and COM-1 (ortholog of Com1/Sae2/CtIP). Unexpectedly, in contrast to MRE-11 and RAD-50, NBS-1 is not required for meiotic DSB formation. Meiotic defects of the nbs-1 mutant are partially suppressed by abrogation of the nonhomologous end-joining (NHEJ) pathway, indicating a role for NBS-1 in antagonizing NHEJ during meiosis. Our data further reveal that NBS-1 and COM-1 play distinct roles in promoting HR and antagonizing NHEJ. We propose a model in which different components of the MRN-C complex work together to couple meiotic DSB formation with efficient and timely engagement of HR, thereby ensuring crossover formation and restoration of genome integrity before the meiotic divisions.

Sign in / Sign up

Export Citation Format

Share Document