scholarly journals Extrachromosomal circular DNA-based amplification and transmission of herbicide resistance in crop weedAmaranthus palmeri

2018 ◽  
Vol 115 (13) ◽  
pp. 3332-3337 ◽  
Author(s):  
Dal-Hoe Koo ◽  
William T. Molin ◽  
Christopher A. Saski ◽  
Jiming Jiang ◽  
Karthik Putta ◽  
...  
Keyword(s):  
Gene Amplification ◽  
Herbicide Resistance ◽  
Germ Cells ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Circular Dna ◽  
Dna Structures ◽  
Meiotic Chromosomes ◽  
Extrachromosomal Elements ◽  
Mitosis And Meiosis

Gene amplification has been observed in many bacteria and eukaryotes as a response to various selective pressures, such as antibiotics, cytotoxic drugs, pesticides, herbicides, and other stressful environmental conditions. An increase in gene copy number is often found as extrachromosomal elements that usually contain autonomously replicating extrachromosomal circular DNA molecules (eccDNAs).Amaranthus palmeri, a crop weed, can develop herbicide resistance to glyphosate [N-(phosphonomethyl) glycine] by amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, the molecular target of glyphosate. However, biological questions regarding the source of the amplifiedEPSPS, the nature of the amplified DNA structures, and mechanisms responsible for maintaining this gene amplification in cells and their inheritance remain unknown. Here, we report that amplifiedEPSPScopies in glyphosate-resistant (GR)A. palmeriare present in the form of eccDNAs with various conformations. The eccDNAs are transmitted during cell division in mitosis and meiosis to the soma and germ cells and the progeny by an as yet unknown mechanism of tethering to mitotic and meiotic chromosomes. We propose that eccDNAs are one of the components of McClintock’s postulated innate systems [McClintock B (1978)Stadler Genetics Symposium] that can rapidly produce soma variation, amplifyEPSPSgenes in the sporophyte that are transmitted to germ cells, and modulate rapid glyphosate resistance through genome plasticity and adaptive evolution.

scholarly journals Unstable amplification of two extrachromosomal elements in alpha-difluoromethylornithine-resistant Leishmania donovani.

1992 ◽  
Vol 12 (12) ◽  
pp. 5499-5507 ◽  
Author(s):  
S Hanson ◽  
S M Beverley ◽  
W Wagner ◽  
B Ullman
Keyword(s):  
Gene Amplification ◽  
Leishmania Donovani ◽  
Molecular Mechanisms ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Unstable Gene ◽  
Extrachromosomal Elements ◽  
Circular Dnas ◽  
Amplification Mechanism

We describe the first example of unstable gene amplification consisting of linear extrachromosomal DNAs in drug-resistant eukaryotic cells. alpha-Difluoromethylornithine (DFMO)-resistant Leishmania donovani with an amplified ornithine decarboxylase (ODC) gene copy number contained two new extrachromosomal DNAs, both present in 10 to 20 copies. One of these was a 140-kb linear DNA (ODC140-L) on which all of the amplified copies of the odc gene were located. The second was a 70-kb circular DNA (ODC70-C) containing an inverted repeat but lacking the odc gene. Both ODC140-L and ODC70-C were derived from a preexisting wild-type chromosome, probably by a conservative amplification mechanism. Both elements were unstable in the absence of DFMO, and their disappearance coincided with a decrease in ODC activity and an increase in DFMO growth sensitivity. These results suggest the possibility that ODC70-C may play a role in DFMO resistance. These data expand the diversity of known amplification mechanisms in eukaryotes to include the simultaneous unstable amplification of both linear and circular DNAs. Further characterization of these molecules will provide insights into the molecular mechanisms underlying gene amplification, including the ability of linear amplified DNAs to acquire telomeres and the determinants of chromosomal stability.

Unstable amplification of two extrachromosomal elements in alpha-difluoromethylornithine-resistant Leishmania donovani

1992 ◽  
Vol 12 (12) ◽  
pp. 5499-5507
Author(s):  
S Hanson ◽  
S M Beverley ◽  
W Wagner ◽  
B Ullman
Keyword(s):  
Gene Amplification ◽  
Leishmania Donovani ◽  
Molecular Mechanisms ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Unstable Gene ◽  
Extrachromosomal Elements ◽  
Circular Dnas ◽  
Amplification Mechanism

We describe the first example of unstable gene amplification consisting of linear extrachromosomal DNAs in drug-resistant eukaryotic cells. alpha-Difluoromethylornithine (DFMO)-resistant Leishmania donovani with an amplified ornithine decarboxylase (ODC) gene copy number contained two new extrachromosomal DNAs, both present in 10 to 20 copies. One of these was a 140-kb linear DNA (ODC140-L) on which all of the amplified copies of the odc gene were located. The second was a 70-kb circular DNA (ODC70-C) containing an inverted repeat but lacking the odc gene. Both ODC140-L and ODC70-C were derived from a preexisting wild-type chromosome, probably by a conservative amplification mechanism. Both elements were unstable in the absence of DFMO, and their disappearance coincided with a decrease in ODC activity and an increase in DFMO growth sensitivity. These results suggest the possibility that ODC70-C may play a role in DFMO resistance. These data expand the diversity of known amplification mechanisms in eukaryotes to include the simultaneous unstable amplification of both linear and circular DNAs. Further characterization of these molecules will provide insights into the molecular mechanisms underlying gene amplification, including the ability of linear amplified DNAs to acquire telomeres and the determinants of chromosomal stability.

Clinical relevance of tumor cell ploidy and N-myc gene amplification in childhood neuroblastoma: a Pediatric Oncology Group study.

1991 ◽  
Vol 9 (4) ◽  
pp. 581-591 ◽  
Author(s):  
A T Look ◽  
F A Hayes ◽  
J J Shuster ◽  
E C Douglass ◽  
R P Castleberry ◽  
...  
Keyword(s):  
Tumor Cell ◽  
Gene Amplification ◽  
Gene Copy Number ◽  
Disease Free Survival ◽  
Gene Copy ◽  
Early Treatment Failure ◽  
Free Survival ◽  
Myc Gene ◽  
Disease Free

We assessed tumor cell DNA content (ploidy) and N-myc gene copy number as predictors of long-term disease-free survival in 298 children with neuroblastoma. Diploid tumor stem lines were identified in 101 patients (34%), clonal hyperdiploid abnormalities in 194 (65%), and hypodiploid stem lines in three (1%). In children with widely disseminated tumors at diagnosis (stage D), ploidy had a highly age-dependent influence on prognosis. Among infants (less than 12 months) treated with cyclophosphamide-doxorubicin, hyperdiploidy was closely associated with long-term disease-free survival (greater than 90% of cases), while diploidy invariably predicted early treatment failure (P less than .001). Similarly, in children 12 to 24 months of age who were treated with cisplatin-teniposide and cyclophosphamide-doxorubicin, diploidy uniformly predicted early failure, whereas half of the children with hyperdiploidy achieved long-term disease-free survival (P less than .001). There was no relationship between ploidy and treatment outcome in children older than 24 months with stage D tumors who had a very low probability of long-term disease-free survival (less than 10%). N-myc gene amplification was detected in 37 (25%) of the 147 tumors tested, with the remainder showing single-copy levels of the gene. N-myc gene amplification was more frequent in diploid than in hyperdiploid tumors (23 of 57 v 14 of 87, P = .001) and predicted a high likelihood of early treatment failure. In children younger than 2 years with disseminated neuroblastoma, tumor cell ploidy and N-myc gene copy number provide complementary prognostic information that will distinguish patients who can be cured on current regimens from those who require new treatment strategies.

MET Gene High Copy Number (Amplification/Polysomy) Identified in Melanoma for Potential Targeted Therapy

2021 ◽  
Author(s):  
Nisha S Ramani ◽  
Ajaykumar C Morani ◽  
Shengle Zhang
Keyword(s):  
Targeted Therapy ◽  
Gene Amplification ◽  
Copy Number ◽  
Kinase Inhibitors ◽  
Gene Copy Number ◽  
Tissue Microarrays ◽  
High Copy Number ◽  
Gene Copy ◽  
Aberrant Expression ◽  
Mesenchymal Epithelial Transition Factor

Abstract Objectives Aberrant expression of the mesenchymal epithelial transition factor (MET) gene has been observed in several malignancies, and drugs targeting the MET gene have been implicated in clinical trials with promising results. Hence, MET is a potentially targetable oncogenic driver. We explored the frequency of MET gene high copy number in melanomas and carcinomas. Methods The study group included 135 patients. Tissue microarrays were constructed with 19 melanomas and 116 carcinomas diagnosed from 2010 to 2012. We screened MET gene copy number by fluorescence in situ hybridization analysis using probes for MET gene and CEP7 as control. Results We found MET gene amplification in 2 (11%) of 19 melanoma cases, whereas 5 (26%) of 19 melanoma cases showed polysomy. For carcinomas, there was no MET gene amplification identified. However, 8 (7%) of 116 cases showed polysomy. Conclusions In our study, MET gene amplification was identified in 11% of melanomas and is relatively concordant with few reported studies. However, about 26% of the additional melanoma cases showed MET gene polysomy, which has not been reported as per our knowledge. If these results are validated with further orthogonal studies, more of the melanoma cases could potentially benefit from targeted therapy with MET tyrosine kinase inhibitors.

Mathematical models of gene amplification with applications to cellular drug resistance and tumorigenicity.

Genetics ◽  
1990 ◽  
Vol 125 (3) ◽  
pp. 633-644
Author(s):  
M Kimmel ◽  
D E Axelrod
Keyword(s):  
Mathematical Models ◽  
Cell Lines ◽  
Gene Amplification ◽  
Dihydrofolate Reductase ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Published Data ◽  
Reductase Gene ◽  
Double Minute ◽  
Double Minute Chromosomes

Abstract An increased number of copies of specific genes may offer an advantage to cells when they grow in restrictive conditions such as in the presence of toxic drugs, or in a tumor. Three mathematical models of gene amplification and deamplification are proposed to describe the kinetics of unstable phenotypes of cells with amplified genes. The models differ in details but all assume probabilistic mechanisms of increase and decrease in gene copy number per cell (gene amplification/deamplification). Analysis of the models indicates that a stable distribution of numbers of copies of genes per cell, observed experimentally, exists only if the probability of deamplification exceeds the probability of amplification. The models are fitted to published data on the loss of methotrexate resistance in cultured cell lines, due to the loss of amplified dihydrofolate reductase gene. For two mouse cell lines unstably resistant to methotrexate the probabilities of amplification and deamplification of the dihydrofolate reductase gene on double minute chromosomes are estimated to be approximately 2% and 10%, respectively. These probabilities are much higher than widely presumed. The models explain the gradual disappearance of the resistant phenotype when selective pressure is withdrawn, by postulating that the rate of deamplification exceeds the rate of amplification. Thus it is not necessary to invoke a growth advantage of nonresistant cells which has been the standard explanation. For another analogous process, the loss of double minute chromosomes containing the myc oncogene from SEWA tumor cells, the growth advantage model does seem to be superior to the amplification and deamplification model. In a more theoretical section of the paper, it is demonstrated that gene amplification/deamplification can result in reduction to homozygosity, such as is observed in some tumors. Other applications are discussed.

Resistance to methotrexate due to gene amplification in a patient with acute leukemia.

1984 ◽  
Vol 2 (1) ◽  
pp. 16-20 ◽  
Author(s):  
M D Carman ◽  
J H Schornagel ◽  
R S Rivest ◽  
S Srimatkandada ◽  
C S Portlock ◽  
...  
Keyword(s):  
Gene Amplification ◽  
Copy Number ◽  
Cdna Probe ◽  
Leukemia Cell ◽  
Gene Copy Number ◽  
Leukemia Cell Line ◽  
Gene Copy ◽  
Acute Myelocytic Leukemia ◽  
Human Leukemia ◽  
Dot Blot

A patient is described with acute myelocytic leukemia refractory to conventional therapy, who also became highly resistant to methotrexate (MTX) after repeated courses of this drug. Leukemia cells from this patient were found to contain an elevated level of dihydrofolate reductase (DHFR) activity, with no change in the affinity of the enzyme for MTX. A sensitive "dot blot" assay revealed a fourfold increase in the gene copy number of DHFR. Southern blot analysis with a human DHFR cDNA probe confirmed this increase in the gene copy number, and demonstrated a similar restriction pattern with Eco R1, Hind III, and Pst 1 as seen with a highly amplified human leukemia cell line, K562. Additional DHFR fragments were detected, not seen in the K562 blot, suggesting the presence of pseudogenes, or a result of gene rearrangements occurring as part of the amplification process. Resistance to MTX in this patient was therefore ascribed to gene amplification and overproduction of DHFR.

Gene copy number of epidermal growth factor receptor (EGFR) by fluorescent in situ hybridization (FISH) in head and neck squamous cell carcinomas (HNSCC) is closely correlated with EGFR protein levels assessed by automated quantitative protein analysis (AQUA)

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 6023-6023
Author(s):  
P. Weinberger ◽  
A. Psyrri ◽  
P. Kountourakis ◽  
T. Rampias ◽  
C. Sasaki ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Protein Expression ◽  
Protein Content ◽  
Gene Amplification ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Egfr Gene ◽  
Protein Levels

6023 Background: EGFR overexpression correlates with recurrence and with treatment resistance in HNSCC. The mechanisms of EGFR protein overexpression are poorly understood. Nonetheless, previous investigators have not demonstrated a correlation between EGFR gene copy number and protein content, using conventional immunohistochemistry (IHC). The aim of this study was to evaluate the relationship of EGFR gene copy number and protein expression utilizing fluorescence in situ hybridization (FISH) and AQUA, a novel, immunohistochemical method of automated quantitative in situ proteomic analysis which permits subcellular localization. Methods: A tissue microarray composed of 137 HNSCC treated with (chemo)radiation was constructed and analyzed for EGFR copy number by FISH (Vysis/Abbot) and EGFR protein expression (DAKO antibody) using AQUA analysis of EGFR staining scored on a scale of 0–255 and by conventional IHC. Agreement was assessed using kappa. Results: Sixteen (15%) of one-hundred six tumors with FISH results demonstrated EGFR high polysomy and/or gene amplification (FISH+). AQUA demonstrated a range of 3.6–102.2; protein levels assessed by AQUA in the FISH amplified cases were significantly higher (p =0.008) than in the FISH non- amplified ones. Using the EGFR 75th percentile as a cut-off, AQUA and FISH showed significant agreement (percentage of overall agreement 82%, kappa=0.458, p=0.003). To the contrary there was no concordance between FISH and conventional IHC results in this series. Conclusions: The discrepancy between EGFR gene amplification rate and protein expression by IHC reported previously may be due to the limitations and nonquantitative nature of conventional IHC. EGFR protein content correlates with gene copy number if protein content is quantitated and automatically analyzed, as with AQUA. No significant financial relationships to disclose.

scholarly journals Analysis of amplicons containing the esterase genes responsible for insecticide resistance in the peach-potato aphid Myzus persicae (Sulzer)

1996 ◽  
Vol 313 (2) ◽  
pp. 543-547 ◽  
Author(s):  
Linda M. FIELD ◽  
Alan L. DEVONSHIRE ◽  
Chris TYLER-SMITH
Keyword(s):  
Gene Amplification ◽  
Myzus Persicae ◽  
Gene Copy Number ◽  
Fold Increase ◽  
Gene Copy ◽  
Potato Aphid ◽  
Gene Copies ◽  
Genes Encoding ◽  
Aphid Clone ◽  
Peach Potato Aphid

The amplification of genes encoding an insecticide-detoxifying esterase (E4) in the peach-potato aphid Myzus persicae is one of the few examples where this genetic phenomenon has been shown to be involved in the response of an intact higher organism to artificial selection. Here we report quantitative and qualitative studies of the repeat units (amplicons) containing the E4 genes in a highly resistant aphid clone. Initial studies to quantify esterase sequences showed a 5-11-fold increase in resistant aphids compared with susceptible aphids, suggesting the presence of 10-22 gene copies per diploid genome. A more incisive analysis by pulsed-field gel electrophoresis confirmed the presence of about 12 copies of the E4 gene and showed them to be on about 24 kb amplicons, arranged as a tandem array of direct repeats. This, together with previous results from crossing experiments and with recent in situ hybridization studies, confirms that the E4 gene amplification in this aphid clone is heterozygous at a single locus. However, these data show that the gene amplification alone cannot account for the approx. 60 times higher levels of E4 protein and its mRNA present in this aphid clone, and therefore resistance must involve changes in both esterase gene copy number and gene expression.

Level of HER2 Gene Amplification Predicts Response and Overall Survival in HER2-Positive Advanced Gastric Cancer Treated With Trastuzumab

2013 ◽  
Vol 31 (35) ◽  
pp. 4445-4452 ◽  
Author(s):  
Carlos Gomez-Martin ◽  
Jose Carlos Plaza ◽  
Roberto Pazo-Cid ◽  
Antonieta Salud ◽  
Francesc Pons ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Overall Survival ◽  
Advanced Gastric Cancer ◽  
Gene Amplification ◽  
Copy Number ◽  
Gene Copy Number ◽  
Gene Copy ◽  
Her2 Gene ◽  
Optimal Cutoff ◽  
Her2 Gene Amplification

Purpose Previous studies have highlighted the importance of an appropriate human epidermal growth factor receptor 2 (HER2) evaluation for the proper identification of patients eligible for treatment with anti-HER2 targeted therapies. Today, the relationship remains unclear between the level of HER2 amplification and the outcome of HER2-positive gastric cancer treated with first-line chemotherapy with trastuzumab. The aim of this study was to determine whether the level of HER2 gene amplification determined by the HER2/CEP17 ratio and HER2 gene copy number could significantly predict some benefit in overall survival and response to therapy in advanced gastric cancer treated with trastuzumab-based chemotherapy. Patients and Methods Ninety patients with metastatic gastric cancer treated with first-line trastuzumab-based chemotherapy were studied. The optimal cutoff values for HER2/CEP17 ratio and HER2 gene copy number (GCN) for discriminating positive results in terms of response and prolonged survival were determined using receiver operating characteristic curves analyses. Results In this study, a median HER2/CEP17 ratio of 6.11 (95% CI, 2.27 to 21.90) and a median HER2 gene copy number of 11.90 (95% CI, 3.30 to 43.80) were found. A mean HER2/CEP17 ratio of 4.7 was identified as the optimal cutoff value discriminating sensitive and refractory patients (P = .005). Similarly, the optimal cutoff for predicting survival longer than 12 months was 4.45 (P = .005), and for survival longer than 16 months was 5.15 (P = .004). For HER2 GCN, the optimal cutoff values were 9.4, 10.0, and 9.5, respectively (P = .02). Conclusion The level of HER2 gene amplification significantly predicts sensitivity to therapy and overall survival in advanced gastric cancer treated with trastuzumab-based chemotherapy.

scholarly journals The eccDNA Replicon: A heritable, extra-nuclear vehicle that enables gene amplification and glyphosate resistance in Amaranthus palmeri

2020 ◽  
Author(s):  
William T. Molin ◽  
Allison Yaguchi ◽  
Mark Blenner ◽  
Christopher A. Saski
Keyword(s):  
Gene Copy Number ◽  
Gene Copy ◽  
Amaranthus Palmeri ◽  
Structural Variations ◽  
Circular Dna ◽  
Amaranthus Hypochondriacus ◽  
Gene Copy Number Variation ◽  
Number Variation ◽  
Repetitive Structure ◽  
Underlying Mechanisms

ABSTRACTGene copy number variation is a predominant mechanism by which organisms respond to selective pressures in nature, which often results in unbalanced structural variations that perpetuate as adaptations to sustain life. However, the underlying mechanisms that give rise to gene proliferation are poorly understood. Here, we show a unique result of genomic plasticity in Amaranthus palmeri, a massive, ∼400kb extrachromosomal circular DNA (eccDNA), that harbors the 5-enoylpyruvylshikimate-3-phosphate synthase (EPSPS) gene and 58 other encoded genes whose functions traverse detoxification, replication, recombination, transposition, tethering, and transport. Gene expression analysis under glyphosate stress showed transcription of 41 of the 59 genes, with high expression of EPSPS, aminotransferase, zinc-finger, and several uncharacterized proteins. The genomic architecture of the eccDNA replicon is comprised of a complex arrangement of repeat sequences and mobile genetic elements interspersed among arrays of clustered palindromes that may be crucial for stability, DNA duplication and tethering, and/or a means of nuclear integration of the adjacent and intervening sequences. Comparative analysis of orthologous genes in grain amaranth (Amaranthus hypochondriacus) and water-hemp (Amaranthus tuberculatus) suggest higher order chromatin interactions contribute to the genomic origins of the Amaranthus palmeri eccDNA replicon structure.One-sentence summaryThe eccDNA replicon is a large extra-nuclear circular DNA that is composed of a sophisticated repetitive structure, harbors the EPSPS and several other genes that are transcribed during glyphosate stress.

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