scholarly journals Centromere clustering stabilizes meiotic homolog pairing

2019 ◽  
Author(s):  
Talia Hatkevich ◽  
Vincent Boudreau ◽  
Thomas Rubin ◽  
Paul S. Maddox ◽  
Jean-René Huynh ◽  
...  
Keyword(s):  
Meiotic Pairing ◽  
Homolog Pairing ◽  
Meiotic Synapsis

ABSTRACTDuring meiosis, each chromosome must selectively pair and synapse with its own unique homolog to enable crossover formation and subsequent segregation. How homolog pairing is maintained in early meiosis to ensure synapsis occurs exclusively between homologs is unknown. We aimed to further understand this process by utilizing a uniqueDrosophilameiotic mutant,Mcm5A7. We found thatMcm5A7mutants are proficient in homolog pairing at meiotic onset yet fail to maintain pairing as meiotic synapsis ensues, causing seemingly-normal synapsis between non-homologous loci. This pairing defect corresponds with a reduction of SMC1-dependent centromere clustering at meiotic onset. Overexpressing SMC1 in this mutant significantly restores centromere clustering, homolog pairing, and crossover formation. These data indicate that the initial meiotic pairing of homologs is not sufficient to yield synapsis between exclusively between homologs and provide a model in which meiotic homolog pairing must be stabilized by SMC1-dependent centromere clustering to ensure proper synapsis.

scholarly journals Oligopaint DNA FISH as a tool for investigating meiotic chromosome dynamics in the silkworm, Bombyx mori

2021 ◽  
Author(s):  
Leah F Rosin ◽  
Jose Gil ◽  
Ines Anna Drinnenberg ◽  
Elissa P Lei
Keyword(s):  
Bombyx Mori ◽  
Meiotic Chromosome ◽  
Low Cost ◽  
Classical Model ◽  
Spindle Pole ◽  
Meiotic Pairing ◽  
Homolog Pairing ◽  
Bivalent Formation ◽  
High Flexibility ◽  
Silkworm Bombyx Mori

Accurate chromosome segregation during meiosis is essential for reproductive success. Yet, many fundamental aspects of meiosis remain unclear, including the mechanisms regulating homolog pairing across species. This gap is partially due to our inability to visualize individual chromosomes during meiosis. Here, we employ Oligopaint FISH to investigate homolog pairing and compaction of meiotic chromosomes in a classical model system, the silkworm Bombyx mori. Our Oligopaint design combines multiplexed barcoding with secondary oligo labeling for high flexibility and low cost. These studies illustrate that Oligopaints are highly specific in whole-mount gonads and on meiotic chromosome spreads. We show that meiotic pairing is robust in both males and female meiosis. Additionally, we show that meiotic bivalent formation in B. mori males is highly similar to bivalent formation in C. elegans, with both of these pathways ultimately resulting in the pairing of chromosome ends with non-paired ends facing the spindle pole and microtubule recruitment independent of the centromere-specifying factor CENP-A.

scholarly journals Modeling meiotic chromosome pairing: increased fidelity from a tug of war between telomere forces and a pairing-based Brownian ratchet

2018 ◽  
Author(s):  
Wallace F. Marshall ◽  
Jennifer C. Fung
Keyword(s):  
Meiotic Chromosome ◽  
Meiotic Pairing ◽  
Dependent Manner ◽  
Brownian Ratchet ◽  
Lower Affinity ◽  
Homolog Pairing ◽  
High Affinity ◽  
Random Forces ◽  
Stall Force ◽  
Do So

AbstractMeiotic homolog pairing involves associations between homologous DNA regions scattered along the length of a chromosome. When homologs associate, they tend to do so by a processive zippering processive, which apparently results from avidity effects. Using a computational model, we show that this avidity-driven processive zippering reduces the selectivity of pairing. When active random forces are applied to telomeres, this drop in selectivity is eliminated in a force-dependent manner. Further simulations suggest that active telomere forces are engaged in a tug-of-war against zippering, which can be interpreted as a Brownian ratchet with a stall force that depends on the dissociation constant of pairing. When perfectly homologous regions of high affinity compete with homeologous regions of lower affinity, the affinity difference can be amplified through this tug of war effect provided the telomere force acts in a range that is strong enough to oppose zippering of homeologs while still permitting zippering of correct homologs. The degree of unzippering depends on the radius of the nucleus, such that complete unzippering of homeologous regions can only take place if the nucleus is large enough to pull the two chromosomes completely apart. A picture of meiotic pairing thus emerges that is fundamentally mechanical in nature, possibly explaining the purpose of active telomere forces, increased nuclear diameter, and the presence of “Maverick” chromosomes in meiosis.

scholarly journals Oligopaint DNA FISH reveals telomere-based meiotic pairing dynamics in the silkworm, Bombyx mori

PLoS Genetics ◽  
2021 ◽  
Vol 17 (7) ◽  
pp. e1009700
Author(s):  
Leah F. Rosin ◽  
Jose Gil ◽  
Ines A. Drinnenberg ◽  
Elissa P. Lei
Keyword(s):  
Bombyx Mori ◽  
Low Cost ◽  
Classical Model ◽  
Super Resolution ◽  
Spindle Pole ◽  
Male Meiosis ◽  
Meiotic Pairing ◽  
Homolog Pairing ◽  
Bivalent Formation ◽  
High Flexibility

Accurate chromosome segregation during meiosis is essential for reproductive success. Yet, many fundamental aspects of meiosis remain unclear, including the mechanisms regulating homolog pairing across species. This gap is partially due to our inability to visualize individual chromosomes during meiosis. Here, we employ Oligopaint FISH to investigate homolog pairing and compaction of meiotic chromosomes and resurrect a classical model system, the silkworm Bombyx mori. Our Oligopaint design combines multiplexed barcoding with secondary oligo labeling for high flexibility and low cost. These studies illustrate that Oligopaints are highly specific in whole-mount gonads and on meiotic squashes. We show that meiotic pairing is robust in both males and females and that pairing can occur through numerous partially paired intermediate structures. We also show that pairing in male meiosis occurs asynchronously and seemingly in a transcription-biased manner. Further, we reveal that meiotic bivalent formation in B. mori males is highly similar to bivalent formation in C. elegans, with both of these pathways ultimately resulting in the pairing of chromosome ends with non-paired ends facing the spindle pole. Additionally, microtubule recruitment in both C. elegans and B. mori is likely dependent on kinetochore proteins but independent of the centromere-specifying histone CENP-A. Finally, using super-resolution microscopy in the female germline, we show that homologous chromosomes remain associated at telomere domains in the absence of chiasma and after breakdown and modification to the synaptonemal complex in pachytene. These studies reveal novel insights into mechanisms of meiotic homolog pairing both with or without recombination.

The initiation of meiotic chromosome pairing: the cytological view

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 759-778 ◽  
Author(s):  
Josef Loidl
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Pairing ◽  
Meiotic Chromosome ◽  
Meiotic Pairing ◽  
Cytological Evidence ◽  
Homologous Chromosomes ◽  
Synaptonemal Complex Formation ◽  
Meiotic Synapsis ◽  
The One ◽  
First Contact

Opposing views are held with respect to the time when and the mechanisms whereby homologous chromosomes find each other for meiotic synapsis. On the one hand, some evidence has been presented for somatic homologous associations or some other kind of relationship between chromosomes in somatic cells as a preliminary to meiotic pairing. On the other hand, it is argued by many that homologous contacts are first established at meiotic prophase prior to, or in the course of, synaptonemal complex formation. The present paper reviews the controversial cytological evidence, hypotheses, and ideas on how the first contact between homologous chromosomes comes about.Key words: synapsis, meiosis, presynaptic alignment, homologous recognition, synaptonemal complex, chromosome pairing.

scholarly journals HOP1: a yeast meiotic pairing gene.

Genetics ◽  
1989 ◽  
Vol 121 (3) ◽  
pp. 445-462 ◽  
Author(s):  
N M Hollingsworth ◽  
B Byers
Keyword(s):  
Synaptonemal Complex ◽  
Structural Basis ◽  
Recessive Mutation ◽  
Intragenic Recombination ◽  
Meiotic Pairing ◽  
Homologous Chromosomes ◽  
Homolog Pairing ◽  
Chromosomal Pairing ◽  
Chromosome Iii ◽  
Cloned Gene

Abstract The recessive mutation, hop1-1, was isolated by use of a screen designed to detect mutations defective in homologous chromosomal pairing during meiosis in Saccharomyces cerevisiae. Mutants in HOP1 displayed decreased levels of meiotic crossing over and intragenic recombination between markers on homologous chromosomes. In contrast, assays of the hop1-1 mutation in a spo13-1 haploid disomic for chromosome III demonstrated that intrachromosomal recombination between directly duplicated sequences was unaffected. The spores produced by SPO13 diploids homozygous for hop1 were largely inviable, as expected for a defect in interhomolog recombination that results in high levels of nondisjunction. HOP1 was cloned by complementation of the spore lethality phenotype and the cloned gene was used to map HOP1 to the LYS11-HIS6 interval on the left arm of chromosome IX. Electron microscopy revealed that diploids homozygous for hop1 fail to form synaptonemal complex, which normally provides the structural basis for homolog pairing. We propose that HOP1 acts in meiosis primarily to promote chromosomal pairing, perhaps by encoding a component of the synaptonemal complex.

scholarly journals Interplay between Pds5 and Rec8 in regulating chromosome axis length and crossover frequency

2021 ◽  
Vol 7 (11) ◽  
pp. eabe7920
Author(s):  
Meihui Song ◽  
Binyuan Zhai ◽  
Xiao Yang ◽  
Taicong Tan ◽  
Ying Wang ◽  
...  
Keyword(s):  
Recombination Frequency ◽  
Crossover Frequency ◽  
Wild Type ◽  
Protein Levels ◽  
Homolog Pairing ◽  
Meiotic Chromosomes ◽  
Homologous Chromosome Pairing ◽  
Axis Length ◽  
Chromosome Axis

Meiotic chromosomes have a loop/axis architecture, with axis length determining crossover frequency. Meiosis-specific Pds5 depletion mutants have shorter chromosome axes and lower homologous chromosome pairing and recombination frequency. However, it is poorly understood how Pds5 coordinately regulates these processes. In this study, we show that only ~20% of wild-type level of Pds5 is required for homolog pairing and that higher levels of Pds5 dosage-dependently regulate axis length and crossover frequency. Moderate changes in Pds5 protein levels do not explicitly impair the basic recombination process. Further investigations show that Pds5 does not regulate chromosome axes by altering Rec8 abundance. Conversely, Rec8 regulates chromosome axis length by modulating Pds5. These findings highlight the important role of Pds5 in regulating meiosis and its relationship with Rec8 to regulate chromosome axis length and crossover frequency with implications for evolutionary adaptation.

Male Sterility and Meiotic Drive Associated With Sex Chromosome Rearrangements in Drosophila: Role of X-Y Pairing

Genetics ◽  
1998 ◽  
Vol 149 (1) ◽  
pp. 143-155 ◽  
Author(s):  
Bruce D McKee ◽  
Kathy Wilhelm ◽  
Cynthia Merrill ◽  
Xiao-jia Ren
Keyword(s):  
Male Sterility ◽  
Sex Chromosome ◽  
Meiotic Drive ◽  
Repeated Sequence ◽  
Meiotic Pairing ◽  
Intergenic Spacers ◽  
Male Specific ◽  
The Relationship ◽  
Novel Model

Abstract In Drosophila melanogaster, deletions of the pericentromeric X heterochromatin cause X-Y nondisjunction, reduced male fertility and distorted sperm recovery ratios (meiotic drive) in combination with a normal Y chromosome and interact with Y-autosome translocations (T(Y;A)) to cause complete male sterility. The pericentromeric heterochromatin has been shown to contain the male-specific X-Y meiotic pairing sites, which consist mostly of a 240-bp repeated sequence in the intergenic spacers (IGS) of the rDNA repeats. The experiments in this paper address the relationship between X-Y pairing failure and the meiotic drive and sterility effects of Xh deletions. X-linked insertions either of complete rDNA repeats or of rDNA fragments that contain the IGS were found to suppress X-Y nondisjunction and meiotic drive in Xh−/Y males, and to restore fertility to Xh−/T(Y;A) males for eight of nine tested Y-autosome translocations. rDNA fragments devoid of IGS repeats proved incapable of suppressing either meiotic drive or chromosomal sterility. These results indicate that the various spermatogenic disruptions associated with X heterochromatic deletions are all consequences of X-Y pairing failure. We interpret these findings in terms of a novel model in which misalignment of chromosomes triggers a checkpoint that acts by disabling the spermatids that derive from affected spermatocytes.

Effect of the Pairing Gene Ph1 and Premeiotic Colchicine Treatment on Intra- and Interchromosome Pairing of Isochromosomes in Common Wheat

Genetics ◽  
1998 ◽  
Vol 150 (3) ◽  
pp. 1199-1208 ◽  
Author(s):  
Juan M Vega ◽  
Moshe Feldman
Keyword(s):  
Common Wheat ◽  
Homologous Chromosome ◽  
Colchicine Treatment ◽  
Crossing Over ◽  
Meiotic Pairing ◽  
Factors Affecting ◽  
Homologous Chromosomes ◽  
Polyploid Wheat ◽  
Main Gene ◽  
Ph1 Gene

Abstract The analysis of the pattern of isochromosome pairing allows one to distinguish factors affecting presynaptic alignment of homologous chromosomes from those affecting synapsis and crossing-over. Because the two homologous arms in an isochromosome are invariably associated by a common centromere, the suppression of pairing between these arms (intrachromosome pairing) would indicate that synaptic or postsynaptic events were impaired. In contrast, the suppression of pairing between an isochromosome and its homologous chromosome (interchromosome pairing), without affecting intrachromosome pairing, would suggest that homologous presynaptic alignment was impaired. We used such an isochromosome system to determine which of the processes associated with chromosome pairing was affected by the Ph1 gene of common wheat—the main gene that restricts pairing to homologues. Ph1 reduced the frequency of interchromosome pairing without affecting intrachromosome pairing. In contrast, intrachromosome pairing was strongly reduced in the absence of the synaptic gene Syn-B1. Premeiotic colchicine treatment, which drastically decreased pairing of conventional chromosomes, reduced interchromosome but not intrachromosome pairing. The results support the hypothesis that premeiotic alignment is a necessary stage for the regularity of meiotic pairing and that Ph1 relaxes this alignment. We suggest that Ph1 acts on premeiotic alignment of homologues and homeologues as a means of ensuring diploid-like meiotic behavior in polyploid wheat.

scholarly journals Chromatid and chromosome type breakage-fusion-bridge cycles in wheat (Triticum aestivum L.).

Genetics ◽  
1995 ◽  
Vol 140 (3) ◽  
pp. 1069-1085 ◽  
Author(s):  
A J Lukaszewski
Keyword(s):  
Triticum Aestivum ◽  
Ring Chromosome ◽  
Triticum Aestivum L ◽  
Aleurone Layer ◽  
Meiotic Pairing ◽  
Chromosome Type ◽  
Root Tips ◽  
Morphological Marker ◽  
Bfb Cycle ◽  
Tandem Duplications

Abstract During the development of disomic additions of rye (Secale cereale L.) chromosomes to wheat (Triticum aestivum L.), two reverse tandem duplications on wheat chromosomes 3D and 4A were isolated. By virtue of their meiotic pairing, the reverse tandem duplications initiated the chromatid type of the breakage-fusion-bridge (BFB) cycle. This BFB cycle continued through pollen mitoses and in the early endosperm divisions, but no clear evidence of its presence in embryo mitoses was found. The chromosome type of BFB cycle was initiated by fusion of two broken chromosome ends resulting in a dicentric or a ring chromosome. Chromosome type BFB cycles were detected in embryo mitoses and in root tips, but they did not persist until the next meiosis and were not transmitted to the progeny. Active BFB cycles induced breakage of other wheat chromosomes that resulted in additional reverse tandem duplications and dicentric and ring chromosomes. Four loci, on chromosome arms 2BS, 3DS, 4AL, and most likely on 7DL, were particularly susceptible to breakage. The BFB cycles produced high frequency of variegation for pigmentation of the aleurone layer of kernels and somatic chimeras for a morphological marker. With the exception of low mutation rate, the observed phenomena are consistent with the activity of a Ds-like element. However, it is not clear whether such an element, if indeed present, was of wheat or rye origin.

Sign in / Sign up

Export Citation Format

Share Document