Established and Novel Mechanisms Leading to de novo Genomic Rearrangements in the Human Germline

2020 ◽  
Vol 160 (4) ◽  
pp. 167-176 ◽  
Author(s):  
Atsushi Hattori ◽  
Maki Fukami
Keyword(s):  
Structural Changes ◽  
De Novo ◽  
Time Window ◽  
Review Article ◽  
Early Embryogenesis ◽  
Genomic Rearrangements ◽  
Dna Breaks ◽  
Replication Errors ◽  
Double Strand Dna Breaks ◽  
Nonallelic Homologous Recombination

During gametogenesis, the human genome can acquire various de novo rearrangements. Most constitutional genomic rearrangements are created through 1 of the 4 well-known mechanisms, i.e., nonallelic homologous recombination, erroneous repair after double-strand DNA breaks, replication errors, and retrotransposition. However, recent studies have identified 2 types of extremely complex rearrangements that cannot be simply explained by these mechanisms. The first type consists of chaotic structural changes in 1 or a few chromosomes that result from “chromoanagenesis (an umbrella term that covers chromothripsis, chromoanasynthesis, and chromoplexy).” The other type is large independent rearrangements in multiple chromosomes indicative of “transient multifocal genomic crisis.” Germline chromoanagenesis (chromothripsis) likely occurs predominantly during spermatogenesis or postzygotic embryogenesis, while multifocal genomic crisis appears to be limited to a specific time window during oogenesis and early embryogenesis or during spermatogenesis. This review article introduces the current understanding of the molecular basis of de novo rearrangements in the germline.

scholarly journals DDRE-24. TARGETING PURINE METABOLISM TO OVERCOME GLIOBLASTOMA THERAPY RESISTANCE

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. i11-i11
Author(s):  
Weihua Zhou ◽  
Yangyang Yao ◽  
Andrew Scott ◽  
Kari Wilder-Romans ◽  
Joseph Dresser ◽  
...  
Keyword(s):  
Cell Lines ◽  
De Novo ◽  
Therapy Resistance ◽  
Dna Breaks ◽  
Purine Synthesis ◽  
Double Strand Dna Breaks ◽  
Ability To Act ◽  
Orally Bioavailable

Abstract Intratumoral genomic heterogeneity in glioblastoma (GBM) is a barrier to overcoming radiation (RT) resistance. To discover genotype-independent mediators of RT resistance, we correlated RT resistance with the concentration of approximately 700 metabolites across 23 GBM cell lines. Purine metabolites, especially those containing the base guanine, were most correlated with RT resistance. Similarly, increased abundance of tumor purines was associated with decreased survival in GBM patients treated with RT. This relationship is causal. Purine supplementation protected RT-sensitive GBMs from RT and promoted the repair of RT-induced double strand DNA breaks (DSBs). In vitro and in vivo stable isotope tracing confirmed that GBM cell lines and orthotopic patient-derived xenografts primarily generated purines through the de novo synthetic pathway. RT treatment further increased de novo purine synthesis in GBM through signaling via the DNA damage response. Inhibition of de novo GTP synthesis with mycophenolic acid (MPA) sensitized multiple GBM cell lines and neurospheres to RT by slowing the repair of RT-induced DSBs. MPA-induced radiosensitization was GTP-dependent as it was rescued by nucleoside supplementation. Modulating pyrimidine metabolism affected neither RT resistance nor DSB repair, suggesting these GTP-specific effects are due to active signaling rather than its ability to act as a physical substrate for DNA repair and candidate signaling molecules have been identified. These results were recapitulated in vivo with mycophenolate mofetil (MMF), the orally bioavailable FDA-approved prodrug of MPA. MMF potentiated RT efficacy, reduced tumor guanylates and slowed the repair of RT-induced DSBs across multiple models. Because de novo purine synthesis is activated by many of the oncogenic alterations that drive GBM, its inhibition is a promising genotype-independent strategy to overcome GBM RT resistance. We have now begun a clinical trial to determine whether combining MMF and RT is safe and potentially efficacious in patients with GBM.

Prime-editors (nickases), hRad51–Cas9 nickase fusions and dCas9 have the same problem as conventional CRISPR-Cas9 of plasmid/Cas9 integration after making a double stranded break

2019 ◽  
Author(s):  
Sandeep Chakraborty
Keyword(s):  
Cellular Response ◽  
Sequencing Data ◽  
Dna Breaks ◽  
Precise Integration ◽  
Guide Rna ◽  
Double Strand Dna Breaks ◽  
Human Therapy ◽  
P53 Activation ◽  
Programmable Nucleases

‘Prime-editing’ proposes to replace traditional programmable nucleases (CRISPR-Cas9) using a catalytically impaired Cas9 (dCas9) connected to a engineered reverse transcriptase, and a guide RNA encoding both the target site and the desired change. With just a ‘nick’ on one strand, it is hypothe- sized, the negative, uncontrollable effects arising from double-strand DNA breaks (DSBs) - translocations, complex proteins, integrations and p53 activation - will be eliminated. However, sequencing data pro- vided (Accid:PRJNA565979) reveal plasmid integration, indicating that DSBs occur. Also, looking at only 16 off-targets is inadequate to assert that Prime-editing is more precise. Integration of plasmid occurs in all three versions (PE1/2/3). Interestingly, dCas9 which is known to be toxic in E. coli and yeast, is shown to have residual endonuclease activity. This also affects studies that use dCas9, like base- editors and de/methylations systems. Previous work using hRad51–Cas9 nickases also show significant integration in on-targets, as well as off-target integration [1]. Thus, we show that cellular response to nicking involves DSBs, and subsequent plasmid/Cas9 integration. This is an unacceptable outcome for any in vivo application in human therapy.

scholarly journals Fine-Structure Mapping of Meiosis-Specific Double-Strand DNA Breaks at a Recombination Hotspot Associated With an Insertion of Telomeric Sequences Upstream of the HIS4 Locus in Yeast

Genetics ◽  
1996 ◽  
Vol 143 (3) ◽  
pp. 1115-1125 ◽  
Author(s):  
Fei Xu ◽  
Thomas D Petes
Keyword(s):  
Meiotic Recombination ◽  
Hydroxyl Groups ◽  
Sequence Specificity ◽  
Structure Mapping ◽  
Dna Breaks ◽  
Exonuclease Iii ◽  
Recombination Hotspot ◽  
Telomeric Sequences ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

Abstract Meiotic recombination in Saccharomyces cerevisiae is initiated by double-strand DNA breaks (DSBs). Using two approaches, we mapped the position of DSBs associated with a recombination hotspot created by insertion of telomeric sequences into the region upstream of HIS4. We found that the breaks have no obvious sequence specificity and localize to a region of ~50 bp adjacent to the telomeric insertion. By mapping the breaks and by studies of the exonuclease III sensitivity of the broken ends, we conclude that most of the broken DNA molecules have blunt ends with 3′-hydroxyl groups.

scholarly journals Competition Between Adjacent Meiotic Recombination Hotspots in the Yeast Saccharomyces cerevisiae

Genetics ◽  
1997 ◽  
Vol 145 (3) ◽  
pp. 661-670 ◽  
Author(s):  
Qing-Qing Fan ◽  
Fei Xu ◽  
Michael A White ◽  
Thomas D Petes
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Recombination ◽  
Telomeric Sequence ◽  
Coding Region ◽  
Dna Breaks ◽  
Local Formation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Recombination Hotspots ◽  
Double Strand Dna Breaks ◽  
His4 Gene

In a wild-type strain of Saccharomyces cerevisiae, a hotspot for meiotic recombination is located upstream of the HIS4 gene. An insertion of a 49-bp telomeric sequence into the coding region of HIS4 strongly stimulates meiotic recombination and the local formation of meiosis-specific double-strand DNA breaks (DSBs). When strains are constructed in which both hotspots are heterozygous, hotspot activity is substantially less when the hotspots are on the same chromosome than when they are on opposite chromosomes.

Expression of double strand DNA breaks repair genes in pterygium

2010 ◽  
Vol 32 (1) ◽  
pp. 39-47 ◽  
Author(s):  
Anna Łękawa–Ilczuk ◽  
Halina Antosz ◽  
Beata Rymgayłło–Jankowska ◽  
Tomasz Żarnowski
Keyword(s):  
Dna Breaks ◽  
Double Strand Dna Breaks ◽  
Repair Genes ◽  
Double Strand Dna

scholarly journals Germline PRKACA amplification causes variable phenotypes that may depend on the extent of the genomic defect: molecular mechanisms and clinical presentations

2015 ◽  
Vol 172 (6) ◽  
pp. 803-811 ◽  
Author(s):  
Maya B Lodish ◽  
Bo Yuan ◽  
Isaac Levy ◽  
Glenn D Braunstein ◽  
Charalampos Lyssikatos ◽  
...  
Keyword(s):  
Copy Number ◽  
Molecular Mechanisms ◽  
De Novo ◽  
Genetic Defect ◽  
Molecular Cytogenetics ◽  
Case Series ◽  
Sporadic Case ◽  
Genomic Rearrangements ◽  
Clinical Presentations ◽  
Depth Analysis

ObjectiveWe have recently reported five patients with bilateral adrenocortical hyperplasia (BAH) and Cushing's syndrome (CS) caused by constitutive activation of the catalytic subunit of protein kinase A (PRKACA). By doing new in-depth analysis of their cytogenetic abnormality, we attempted a better genotype–phenotype correlation of theirPRKACAamplification.DesignThis study is a case series.MethodsMolecular cytogenetic, genomic, clinical, and histopathological analyses were performed in five patients with CS.ResultsReinvestigation of the defects of previously described patients by state-of-the-art molecular cytogenetics showed complex genomic rearrangements in the chromosome 19p13.2p13.12 locus, resulting in copy number gains encompassing the entirePRKACAgene; three patients (one sporadic case and two related cases) were observed with gains consistent with duplications, while two sporadic patients were observed with gains consistent with triplications. Although all five patients presented with ACTH-independent CS, the three sporadic patients had micronodular BAH and underwent bilateral adrenalectomy in early childhood, whereas the two related patients, a mother and a son, presented with macronodular BAH as adults. In at least one patient,PRKACAtriplication was associated with a more severe phenotype.ConclusionsConstitutional chromosomalPRKACAgene amplification is a recently identified genetic defect associated with CS, a trait that may be inherited in an autosomal dominant manner or occurde novo. Genomic rearrangements can be complex and can result in different copy number states of dosage-sensitive genes, e.g., duplication and triplication.PRKACAamplification can lead to variable phenotypes clinically and pathologically, both micro- and macro-nodular BAH, the latter of which we speculate may depend on the extent of amplification.

Inside Back Cover: Double-Strand DNA Breaks Induced by Paracyclophane Gold(I) Complexes (Chem. Eur. J. 26/2017)

2017 ◽  
Vol 23 (26) ◽  
pp. 6459-6459
Author(s):  
Sebastian Bestgen ◽  
Carmen Seidl ◽  
Thomas Wiesner ◽  
Andreas Zimmer ◽  
Martina Falk ◽  
...  
Keyword(s):  
Dna Breaks ◽  
Back Cover ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

Sperm DNA Fragmentation

2021 ◽  
Author(s):  
Stamatios Karavolos
Keyword(s):  
Dna Fragmentation ◽  
Current Data ◽  
Low Fertility ◽  
Current Evidence ◽  
Sperm Dna Fragmentation ◽  
Dna Breaks ◽  
Dna Quality ◽  
Double Strand Dna Breaks ◽  
Sperm Dna ◽  
Clinically Significant

AbstractSperm DNA fragmentation refers to the accumulation of adducts as well as single- or double-strand DNA breaks and reflects the sperm DNA quality. Current data suggest that there are differences in sperm DNA quality among individuals with high or low fertility, and this observation has led to the idea that testing sperm DNA fragmentation could be a useful test of male fertility. However, sperm DNA fragmentation has become one of the most frequently debated topics in reproductive medicine, as there is no agreement about the optimal way to test for DNA fragmentation, the clinically significant level of sperm DNA fragmentation, as well as the best therapeutic options for infertile men. This article presents current evidence related to sperm DNA fragmentation and its role in managing male infertility.

Roles of Caenorhabditis elegans WRN Helicase in DNA Damage Responses, and a Comparison with Its Mammalian Homolog: A Mini-Review

Gerontology ◽  
2015 ◽  
Vol 62 (3) ◽  
pp. 296-303 ◽  
Author(s):  
Jin-Sun Ryu ◽  
Hyeon-Sook Koo
Keyword(s):  
Dna Damage ◽  
Caenorhabditis Elegans ◽  
Werner Syndrome ◽  
Model Organisms ◽  
Current Status ◽  
Helicase Domain ◽  
Replication Forks ◽  
Dna Breaks ◽  
Double Strand Dna Breaks ◽  
Double Strand Dna

Werner syndrome protein (WRN) is unusual among RecQ family DNA helicases in having an additional exonuclease activity. WRN is involved in the repair of double-strand DNA breaks via the homologous recombination and nonhomologous end joining pathways, and also in the base excision repair pathway. In addition, the protein promotes the recovery of stalled replication forks. The helicase activity is thought to unwind DNA duplexes, thereby moving replication forks or Holliday junctions. The targets of the exonuclease could be the nascent DNA strands at a replication fork or the ends of double-strand DNA breaks. However, it is not clear which enzyme activities are essential for repairing different types of DNA damage. Model organisms such as mice, flies, and worms deficient in WRN homologs have been investigated to understand the physiological results of defects in WRN activity. Premature aging, the most remarkable characteristic of Werner syndrome, is also seen in the mutant mice and worms, and hypersensitivity to DNA damage has been observed in WRN mutants of all three model organisms, pointing to conservation of the functions of WRN. In the nematode Caenorhabditis elegans, the WRN homolog contains a helicase domain but no exonuclease domain, so that this animal is very useful for studying the in vivo functions of the helicase without interference from the activity of the exonuclease. Here, we review the current status of investigations of C. elegans WRN-1 and discuss its functional differences from the mammalian homologs.

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