Meiotic Recombination Differences in Rams from Three Breeds of Sheep in the US

2018 ◽  
Vol 156 (2) ◽  
pp. 106-116
Author(s):  
Kimberly M. Davenport ◽  
Stephanie McKay ◽  
Alan G. Fahey ◽  
Clare Gill ◽  
Brenda M. Murdoch
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Chromosome Pair ◽  
Homologous Chromosome ◽  
Homologous Chromosomes ◽  
Important Contributor ◽  
The Us ◽  
Chromosome Arm

Meiotic recombination is an important contributor to genetic variation and ensures proper chromosome segregation during gametogenesis. Previous studies suggest that at least 1 crossover (CO) per chromosome arm is important to avoid mis-segregation. While the total number of COs per spermatocyte is known to differ in mice, this is only beginning to be evaluated in sheep. This study used a cytogenetic approach to quantify and compare the number of COs per spermatocyte in rams from 3 breeds of sheep: Suffolk, Icelandic, and Targhee. In total, 2,758 spermatocytes and over 170,000 COs were examined. Suffolk rams exhibited the lowest mean number of COs (61.1 ± 0.15) compared to Icelandic (63.5 ± 0.27) and Targhee (65.9 ± 0.26) rams. Significant differences in the number of COs per spermatocyte were observed between Suffolk, Icelandic, and Targhee breeds as well as within each breed. Additionally, the number and location of COs were characterized for homologous chromosomes in a subset of spermatocytes for each ram. A positive correlation was identified between the number of COs and the length of the homologous chromosome pair. Suffolk and Icelandic rams exhibited up to 7 COs per chromosome, while Targhee rams exhibited up to 9. Further, distinct CO location preferences on homologous chromosome pairs with 1, 2, 3, and 4 COs were observed in all 3 breeds. These data in sheep will aid in elucidating the mechanism of mammalian meiotic recombination, an important contributor to genetic diversity.

scholarly journals Recombination patterns in maize reveal limits to crossover homeostasis

2015 ◽  
Vol 112 (52) ◽  
pp. 15982-15987 ◽  
Author(s):  
Gaganpreet K. Sidhu ◽  
Celestia Fang ◽  
Mischa A. Olson ◽  
Matthieu Falque ◽  
Olivier C. Martin ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Chromosome Pair ◽  
Double Strand Breaks ◽  
Chromosomal Dna ◽  
Strand Breaks ◽  
Homologous Chromosomes ◽  
Physiological Conditions ◽  
Transgenic Lines

During meiotic recombination, double-strand breaks (DSBs) are formed in chromosomal DNA and then repaired as either crossovers (COs) or non–crossovers (NCOs). In most taxa, the number of DSBs vastly exceeds the number of COs. COs are required for generating genetic diversity in the progeny, as well as proper chromosome segregation. Their formation is tightly controlled so that there is at least one CO per pair of homologous chromosomes whereas the maximum number of COs per chromosome pair is fairly limited. One of the main mechanisms controlling the number of recombination events per meiosis is CO homeostasis, which maintains a stable CO number even when the DSB number is dramatically altered. The existence of CO homeostasis has been reported in several species, including mouse, yeast, and Caenorhabditis elegans. However, it is not known whether homeostasis exists in the same form in all species. In addition, the studies of homeostasis have been conducted using mutants and/or transgenic lines exhibiting fairly severe meiotic phenotypes, and it is unclear how important homeostasis is under normal physiological conditions. We found that, in maize, CO control is robust only to ensure one CO per chromosome pair. However, once this limit is reached, the CO number is linearly related to the DSB number. We propose that CO control is a multifaceted process whose different aspects have a varying degree of importance in different species.

Making crossovers during meiosis

2005 ◽  
Vol 33 (6) ◽  
pp. 1451-1455 ◽  
Author(s):  
M.C. Whitby
Keyword(s):  
Genetic Variation ◽  
Homologous Recombination ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Meiotic Division ◽  
Holliday Junctions ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Dna Junctions

Homologous recombination (HR) is required to promote both correct chromosome segregation and genetic variation during meiosis. For this to be successful recombination intermediates must be resolved to generate reciprocal exchanges or ‘crossovers’ between the homologous chromosomes (homologues) during the first meiotic division. Crossover recombination promotes faithful chromosome segregation by establishing connections (chiasmata) between the homologues, which help guide their proper bipolar alignment on the meiotic spindle. Recent studies of meiotic recombination in both the budding and fission yeasts have established that there are at least two pathways for generating crossovers. One pathway involves the resolution of fully ligated four-way DNA junctions [HJs (Holliday junctions)] by an as yet unidentified endonuclease. The second pathway appears to involve the cleavage of the precursors of ligated HJs, namely displacement (D) loops and unligated/nicked HJs, by the Mus81-Eme1/Mms4 endonuclease.

scholarly journals A compartmentalized, self-extinguishing signaling network mediates crossover control in meiosis

2017 ◽  
Author(s):  
Liangyu Zhang ◽  
Simone Köhler ◽  
Regina Rillo-Bohn ◽  
Abby F. Dernburg
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Molecular Basis ◽  
Chromosome Pair ◽  
Ring Finger ◽  
Cytological Analysis ◽  
Homologous Chromosomes ◽  
Crossover Interference ◽  
C Elegans ◽  
Ring Finger Proteins

AbstractMeiotic recombination between homologous chromosomes is tightly regulated to ensure proper chromosome segregation. Each chromosome pair typically undergoes at least one crossover event (crossover assurance) but these exchanges are also strictly limited in number and widely spaced along chromosomes (crossover interference). This has implied the existence of chromosome-wide signals that regulate crossovers, but their molecular basis remains mysterious. Here we characterize a family of four related RING finger proteins in C. elegans. These proteins are recruited to the synaptonemal complex between paired homologs, where they act as two heterodimeric complexes, likely as E3 ubiquitin ligases. Genetic and cytological analysis reveals that they act with additional components to create a self-extinguishing circuit that controls crossover designation and maturation. These proteins also act at the top of a hierarchical chromosome remodeling process that enables crossovers to direct stepwise segregation. Work in diverse phyla indicates that related mechanisms mediate crossover control across eukaryotes.

scholarly journals Linked-read sequencing of gametes allows efficient genome-wide analysis of meiotic recombination

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Hequan Sun ◽  
Beth A. Rowan ◽  
Pádraic J. Flood ◽  
Ronny Brandt ◽  
Janina Fuss ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Whole Genome ◽  
Fine Scale ◽  
Simultaneous Generation ◽  
Genome Wide Analysis ◽  
Recombinant Plant ◽  
Genome Wide ◽  
Large Populations

Abstract Meiotic crossovers (COs) ensure proper chromosome segregation and redistribute the genetic variation that is transmitted to the next generation. Large populations and the demand for genome-wide, fine-scale resolution challenge existing methods for CO identification. Taking advantage of linked-read sequencing, we develop a highly efficient method for genome-wide identification of COs at kilobase resolution in pooled recombinants. We first test this method using a pool of Arabidopsis F2 recombinants, and recapitulate results obtained from the same plants using individual whole-genome sequencing. By applying this method to a pool of pollen DNA from an F1 plant, we establish a highly accurate CO landscape without generating or sequencing a single recombinant plant. The simplicity of this approach enables the simultaneous generation and analysis of multiple CO landscapes, accelerating the pace at which mechanisms for the regulation of recombination can be elucidated through efficient comparisons of genotypic and environmental effects on recombination.

scholarly journals Massive crossover elevation via combination of HEI10 and recq4a recq4b during Arabidopsis meiosis

2018 ◽  
Vol 115 (10) ◽  
pp. 2437-2442 ◽  
Author(s):  
Heïdi Serra ◽  
Christophe Lambing ◽  
Catherine H. Griffin ◽  
Stephanie D. Topp ◽  
Divyashree C. Nageswaran ◽  
...  
Keyword(s):  
Meiotic Recombination ◽  
Homologous Chromosome ◽  
Crop Improvement ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Homologous Chromosomes ◽  
Meiotic Dsbs ◽  
Competing Pathways

During meiosis, homologous chromosomes undergo reciprocal crossovers, which generate genetic diversity and underpin classical crop improvement. Meiotic recombination initiates from DNA double-strand breaks (DSBs), which are processed into single-stranded DNA that can invade a homologous chromosome. The resulting joint molecules can ultimately be resolved as crossovers. In Arabidopsis, competing pathways balance the repair of ∼100–200 meiotic DSBs into ∼10 crossovers per meiosis, with the excess DSBs repaired as noncrossovers. To bias DSB repair toward crossovers, we simultaneously increased dosage of the procrossover E3 ligase gene HEI10 and introduced mutations in the anticrossovers helicase genes RECQ4A and RECQ4B. As HEI10 and recq4a recq4b increase interfering and noninterfering crossover pathways, respectively, they combine additively to yield a massive meiotic recombination increase. Interestingly, we also show that increased HEI10 dosage increases crossover coincidence, which indicates an effect on interference. We also show that patterns of interhomolog polymorphism and heterochromatin drive recombination increases distally towards the subtelomeres in both HEI10 and recq4a recq4b backgrounds, while the centromeres remain crossover suppressed. These results provide a genetic framework for engineering meiotic recombination landscapes in plant genomes.

scholarly journals Variation of the meiotic recombination landscape and properties over a broad evolutionary distance in yeasts

2017 ◽  
Author(s):  
Christian Brion ◽  
Sylvain Legrand ◽  
Jackson Peter ◽  
Claudia Caradec ◽  
David Pflieger ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Yeast Species ◽  
Budding Yeast ◽  
Evolutionary Distance ◽  
Model Organisms ◽  
Model Species ◽  
Recombination Hotspots ◽  
Chromosome Arm

AbstractMeiotic recombination is a major factor of genome evolution, deeply characterized in only a few model species, notably the yeast Saccharomyces cerevisiae. Consequently, little is known about variations of its properties across species. In this respect, we explored the recombination landscape of Lachancea kluyveri, a protoploid yeast species that diverged from the Saccharomyces genus more than 100 million years ago and we found striking differences with S. cerevisiae. These variations include a lower recombination rate, a higher frequency of chromosomes segregating without any crossover and the absence of recombination on the chromosome arm containing the sex locus. In addition, although well conserved within the Saccharomyces clade, the S. cerevisiae recombination hotspots are not conserved over a broader evolutionary distance. Finally and strikingly, we found evidence of frequent reversion of meiotic commitment to mitotic growth allowing allele shuffling without meiosis completion. Identification of this major but underestimated evolutionary phenomenon illustrates the relevance of exploring non-model species.Author summaryMeiotic recombination promotes accurate chromosome segregation and genetic diversity. To date, the mechanisms and rules lying behind recombination were dissected using model organisms such as the budding yeast Saccharomyces cerevisiae. To assess the conservation and variation of this process over a broad evolutionary distance, we explored the meiotic recombination landscape in Lachancea kluyveri, a budding yeast species that diverged from S. cerevisiae more than 100 million years ago. The meiotic recombination map we generated revealed that the meiotic recombination landscape and properties significantly vary across distantly related yeast species, supporting that recombination hotspots conservation across yeast species is likely associated to the conservation of synteny. Finally, the frequent meiotic reversions we observed led us to re-evaluate their evolutionary importance.

scholarly journals Meiotic effects of MSH4 copy number variation support an adaptive role for post-polyploidy gene loss

2018 ◽  
Author(s):  
Adrián Gonzalo ◽  
Marie-Odile Lucas ◽  
Catherine Marquis ◽  
Andrew Lloyd ◽  
Eric Jenczewski
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Copy Number ◽  
Gene Loss ◽  
Duplicate Gene ◽  
Single Copy ◽  
Homologous Chromosomes ◽  
Evolutionary Forces ◽  
Copy Numbers ◽  
Number Variation

ABSTRACTMany eukaryotes descend from polyploid ancestors that experienced massive duplicate gene loss. This genomic erosion is particularly strong for duplicated (meiotic) recombination genes that return to a single copy more rapidly than genome average following polyploidy. To better understand the evolutionary forces underlying duplicate loss, we analysed how varying copy numbers of MSH4, an essential meiotic recombination gene, influences crossover formation in allotetraploid Brassica napus. We show that faithful chromosome segregation and crossover frequencies between homologous chromosomes are unchanged with MSH4 duplicate loss; by contrast, crossovers between homoeologous chromosomes (which result in genomic rearrangements) decrease with reductions in MSH4 copy number. We also found that inter-homoeologue crossovers originate almost exclusively from the MSH4-dependent crossover pathway. Limiting the efficiency of this pathway by decreasing the copy number of key meiotic recombination genes could therefore contribute to adaptation to polyploidy, by promoting regular chromosome segregation and genomic stability.

scholarly journals Mammalian CNTD1 is critical for meiotic crossover maturation and deselection of excess precrossover sites

2014 ◽  
Vol 205 (5) ◽  
pp. 633-641 ◽  
Author(s):  
J. Kim Holloway ◽  
Xianfei Sun ◽  
Rayka Yokoo ◽  
Anne M. Villeneuve ◽  
Paula E. Cohen
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Homologous Chromosome ◽  
Ring Finger ◽  
Double Strand Breaks ◽  
Related Protein ◽  
Strand Breaks ◽  
Meiotic Crossover ◽  
Specific Factors ◽  
Ring Finger Proteins

Meiotic crossovers (COs) are crucial for ensuring accurate homologous chromosome segregation during meiosis I. Because the double-strand breaks (DSBs) that initiate meiotic recombination greatly outnumber eventual COs, this process requires exquisite regulation to narrow down the pool of DSB intermediates that may form COs. In this paper, we identify a cyclin-related protein, CNTD1, as a critical mediator of this process. Disruption of Cntd1 results in failure to localize CO-specific factors MutLγ and HEI10 at designated CO sites and also leads to prolonged high levels of pre-CO intermediates marked by MutSγ and RNF212. These data show that maturation of COs is intimately coupled to deselection of excess pre-CO sites to yield a limited number of COs and that CNTD1 coordinates these processes by regulating the association between the RING finger proteins HEI10 and RNF212 and components of the CO machinery.

scholarly journals Massive crossover elevation via combination of HEI10 and recq4a recq4b during Arabidopsis meiosis

2017 ◽  
Author(s):  
Heïdi Serra ◽  
Christophe Lambing ◽  
Catherine H. Griffin ◽  
Stephanie D. Topp ◽  
Mathilde Séguéla-Arnaud ◽  
...  
Keyword(s):  
Meiotic Recombination ◽  
Homologous Chromosome ◽  
Crop Improvement ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Dsb Repair ◽  
Strand Breaks ◽  
Homologous Chromosomes ◽  
Meiotic Dsbs ◽  
Competing Pathways

AbstractDuring meiosis homologous chromosomes undergo reciprocal crossovers, which generate genetic diversity and underpin classical crop improvement. Meiotic recombination initiates from DNA double strand breaks, which are processed into single-stranded DNA that can invade a homologous chromosome. The resulting joint molecules can ultimately be resolved as crossovers. In Arabidopsis, competing pathways balance the repair of ∼100–200 meiotic DSBs into ∼10 crossovers per meiosis, with the excess DSBs repaired as non-crossovers. In order to bias DSB repair towards crossovers, we simultaneously increased dosage of the pro-crossover E3 ligase gene HEI10 and introduced mutations in the anti-crossover helicase genes RECQ4A and RECQ4B. As HEI10 and recq4a recq4b increase interfering and non-interfering crossover pathways respectively, they combine additively to yield a massive meiotic recombination increase. Interestingly, we also show that increased HEI10 dosage increases crossover coincidence, which indicates an effect of HEI10 on interference. We also show that patterns of interhomolog polymorphism and heterochromatin drive recombination increases towards the sub-telomeres in both HEI10 and recq4a recq4b backgrounds, while the centromeres remain crossover-suppressed. These results provide a genetic framework for engineering meiotic recombination landscapes in plant genomes.

scholarly journals The rec102 mutant of yeast is defective in meiotic recombination and chromosome synapsis.

Genetics ◽  
1992 ◽  
Vol 130 (1) ◽  
pp. 59-69
Author(s):  
J Bhargava ◽  
J Engebrecht ◽  
G S Roeder
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Meiotic Chromosome ◽  
Crossing Over ◽  
Homologous Chromosomes ◽  
Chromosome Synapsis ◽  
Recombination Pathway ◽  
Yeast Mutants ◽  
Meiosis I

Abstract A mutation at the REC102 locus was identified in a screen for yeast mutants that produce inviable spores. rec102 spore lethality is rescued by a spo13 mutation, which causes cells to bypass the meiosis I division. The rec102 mutation completely eliminates meiotically induced gene conversion and crossing over but has no effect on mitotic recombination frequencies. Cytological studies indicate that the rec102 mutant makes axial elements (precursors to the synaptonemal complex), but homologous chromosomes fail to synapse. In addition, meiotic chromosome segregation is significantly delayed in rec102 strains. Studies of double and triple mutants indicate that the REC102 protein acts before the RAD52 gene product in the meiotic recombination pathway. The REC102 gene was cloned based on complementation of the mutant defect and the gene was mapped to chromosome XII between CDC25 and STE11.

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