Publications by authors named "Daniela Cimini"

53 Publications

Survey of diagnostic and typing capacity for enterovirus infection in Italy and identification of two echovirus 30 outbreaks.

J Clin Virol 2021 Apr 27;137:104763. Epub 2021 Feb 27.

Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy. Electronic address:

Background: Enterovirus infections can cause a variety of illnesses, ranging from asymptomatic infections to severe illness and death.

Aim: To support polio eradication activities, in February 2019, the WHO Regional Reference Laboratory for polio in Italy, at the National Institute of Public Health (Istituto Superiore di Sanità), promoted an investigation on non-polio enterovirus laboratory capacity, with the support of the Italian Ministry of Health. The aim was to collect data on the assays used routinely for diagnostic purposes and to characterize enterovirus outbreaks strains by sequence analysis of the Viral Protein 1 region.

Methods: A questionnaire was administered to public health laboratories through all Italian Regions for 2018 and subsequently, an electronic form for lab-confirmed enterovirus infection reported from February 2019 to January 2020, including patients clinical characteristics, and laboratory data was distributed through 25 laboratories participating the survey.

Results: Overall, a homogenous laboratory capacity for enterovirus infection diagnosis was found and 21,000 diagnostic tests were retrospectively reported in 2018. Then, in 2019, two outbreaks of Echovirus 30 were identified and confirmed by molecular analyses.

Conclusion: These results underline the need monitor the circulation of non-polio enterovirus to ascertain the real burden of the disease in the country.
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http://dx.doi.org/10.1016/j.jcv.2021.104763DOI Listing
April 2021

Spindle Architectural Features Must Be Considered Along With Cell Size to Explain the Timing of Mitotic Checkpoint Silencing.

Front Physiol 2020 28;11:596263. Epub 2021 Jan 28.

Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA, United States.

Mitosis proceeds through a defined series of events that is largely conserved, but the amount of time needed for their completion can vary in different cells and organisms. In many systems, mitotic duration depends on the time required to satisfy and silence the spindle assembly checkpoint (SAC), also known as the mitotic checkpoint. Because SAC silencing involves trafficking SAC molecules among kinetochores, spindle, and cytoplasm, the size and geometry of the spindle relative to cell volume are expected to affect mitotic duration by influencing the timing of SAC silencing. However, the relationship between SAC silencing, cell size, and spindle dimensions is unclear. To investigate this issue, we used four DLD-1 tetraploid (4N) clones characterized by small or large nuclear and cell size. We found that the small 4N clones had longer mitotic durations than the parental DLD-1 cells and that this delay was due to differences in their metaphase duration. Leveraging a previous mathematical model for spatiotemporal regulation of SAC silencing, we show that the difference in metaphase duration, i.e., SAC silencing time, can be explained by the distinct spindle microtubule densities and sizes of the cell, spindle, and spindle poles in the 4N clones. Lastly, we demonstrate that manipulating spindle geometry can alter mitotic and metaphase duration, consistent with a model prediction. Our results suggest that spindle size does not always scale with cell size in mammalian cells and cell size is not sufficient to explain the differences in metaphase duration. Only when a number of spindle architectural features are considered along with cell size can the kinetics of SAC silencing, and hence mitotic duration, in the different clones be explained.
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http://dx.doi.org/10.3389/fphys.2020.596263DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7877541PMC
January 2021

Asymmetric clustering of centrosomes defines the early evolution of tetraploid cells.

Elife 2020 04 29;9. Epub 2020 Apr 29.

Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, United States.

Tetraploidy has long been of interest to both cell and cancer biologists, partly because of its documented role in tumorigenesis. A common model proposes that the extra centrosomes that are typically acquired during tetraploidization are responsible for driving tumorigenesis. However, tetraploid cells evolved in culture have been shown to lack extra centrosomes. This observation raises questions about how tetraploid cells evolve and more specifically about the mechanisms(s) underlying centrosome loss. Here, using a combination of fixed cell analysis, live cell imaging, and mathematical modeling, we show that populations of newly formed tetraploid cells rapidly evolve in vitro to retain a near-tetraploid chromosome number while losing the extra centrosomes gained at the time of tetraploidization. This appears to happen through a process of natural selection in which tetraploid cells that inherit a single centrosome during a bipolar division with asymmetric centrosome clustering are favored for long-term survival.
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http://dx.doi.org/10.7554/eLife.54565DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7250578PMC
April 2020

Aneuploidy and gene expression: is there dosage compensation?

Epigenomics 2019 12 22;11(16):1827-1837. Epub 2019 Nov 22.

Department of Biological Sciences & Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA 24061, USA.

Aneuploidy (i.e., abnormal chromosome number) is the leading cause of miscarriage and congenital defects in humans. Moreover, aneuploidy is ubiquitous in cancer. The deleterious phenotypes associated with aneuploidy are likely a result of the imbalance in the levels of gene products derived from the additional chromosome(s). Here, we summarize the current knowledge on how the presence of extra chromosomes impacts gene expression. We describe studies that have found a strict correlation between gene dosage and transcript levels as wells as studies that have found a less stringent correlation, hinting at the possible existence of dosage compensation mechanisms. We conclude by peering into the epigenetic changes found in aneuploid cells and outlining current knowledge gaps and potential areas of future investigation.
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http://dx.doi.org/10.2217/epi-2019-0135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7132608PMC
December 2019

[Vaccination among healthcare workers in Italy: a narrative review].

Ig Sanita Pubbl 2019 Mar-Apr;75(2):158-173

Sezione di Igiene, Istituto di Sanità Pubblica, Università Cattolica del Sacro Cuore, Roma, Italia.

Vaccination of healthcare workers (HCWs) is a public health tool of the utmost importance and the Italian National Vaccine Prevention Plan (PNPV) 2017-2019 recommends several vaccinations in this population group. Nevertheless, vaccine hesitancy is influencing HCWs' attitude towards vaccination. Moreover, a large number of measles cases have been reported in Italy among HCWs in 2017 and 2018. In Italy there is no national registry for vaccinations, so data on vaccine coverage among HCWs are not readily accessible. The aim of this literature review is to describe the most recent data about vaccination coverage among HCWs in Italy. We also report studies that evaluated the effectiveness of strategies to increase influenza vaccine uptake. We included all studies conducted in Italy and published between 2008 and 2018, regarding vaccines recommended by the PNPV 2017-2019 (hepatitis B, influenza, pertussis, measles, mumps, rubella, varicella, and tuberculosis). Our findings confirm that low vaccination coverage levels among HCWs exist in several Italian regions and cities, highlighting a relevant gap towards targets set by the PNPV. Studies that evaluated the effectiveness of multicomponent interventions to increase vaccination coverage found only minimal to moderate increases in uptake levels. It is therefore crucial to tackle vaccine hesitancy in HCWs, by identifying effective strategies able to significantly increase vaccine coverage, in order to decrease the risk of nosocomial infections, prevent transmission of preventable diseases to patients, and reduce indirect costs related to HCW absenteeism due to illness.
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October 2019

Single-Cell Analysis Reveals that Chronic Silver Nanoparticle Exposure Induces Cell Division Defects in Human Epithelial Cells.

Int J Environ Res Public Health 2019 06 11;16(11). Epub 2019 Jun 11.

Department of Biological Sciences and Fralin Life Sciences Institute, Virginia Tech, Blacksburg, VA 24061, USA.

Multiple organizations have urged a paradigm shift from traditional, whole animal, chemical safety testing to alternative methods. Although these forward-looking methods exist for risk assessment and predication, animal testing is still the preferred method and will remain so until more robust cellular and computational methods are established. To meet this need, we aimed to develop a new, cell division-focused approach based on the idea that defective cell division may be a better predictor of risk than traditional measurements. To develop such an approach, we investigated the toxicity of silver nanoparticles (AgNPs) on human epithelial cells. AgNPs are the type of nanoparticle most widely employed in consumer and medical products, yet toxicity reports are still confounding. Cells were exposed to a range of AgNP doses for both short- and-long term exposure times. The analysis of treated cell populations identified an effect on cell division and the emergence of abnormal nuclear morphologies, including micronuclei and binucleated cells. Overall, our results indicate that AgNPs impair cell division, not only further confirming toxicity to human cells, but also highlighting the propagation of adverse phenotypes within the cell population. Furthermore, this work illustrates that cell division-based analysis will be an important addition to future toxicology studies.
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http://dx.doi.org/10.3390/ijerph16112061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6603987PMC
June 2019

Chromosomes missegregated into micronuclei contribute to chromosomal instability by missegregating at the next division.

Oncotarget 2019 Apr 12;10(28):2660-2674. Epub 2019 Apr 12.

Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA.

Micronuclei (MNi) are extranuclear DNA-containing structures that form upon mitotic exit from unsegregated chromosome fragments or anaphase lagging (whole) chromosomes (LCs). MNi formed from whole chromosomes are of particular interest because LCs are observed in both cancer and non-cancer cells, and are recognized as a major source of chromosomal instability (CIN) in cancer cells. Here, we generated a PtK1 cell line expressing a photoactivatable H2B histone to study the behavior of whole chromosome-containing MNi at the mitosis following their formation. Importantly, MNi of PtK1 cells did not display the membrane rupture or transport defects reported for other cell types. Despite this, we found that most micronucleated cells displayed some kind of chromosome segregation defect and that the missegregating chromosome was the one derived from the MN. Moreover, condensation of the chromosome within the MN was frequently delayed and associated with failure to align at the metaphase plate. Finally, the defective condensation of the MN-derived chromosomes could also explain the frequent occurrence of cytokinesis failure in micronucleated cells. In summary, we find that chromosomes from MNi may trigger a CIN phenotype by missegregating at the mitosis following MN formation.
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http://dx.doi.org/10.18632/oncotarget.26853DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6505630PMC
April 2019

Exogenous glucocorticoids amplify the costs of infection by reducing resistance and tolerance, but effects are mitigated by co-infection.

Proc Biol Sci 2019 04;286(1900):20182913

2 Department of Biological Sciences, Virginia Tech , Blacksburg, VA , USA.

Individual variation in parasite defences, such as resistance and tolerance, can underlie heterogeneity in fitness and could influence disease transmission dynamics. Glucocorticoid hormone concentrations often change in response to fluctuating environmental conditions and mediate changes in immune function, resource allocation and tissue repair. Thus, changes in glucocorticoid hormone concentrations might mediate individual variation in investment in resistance versus tolerance. In this study, we experimentally increased glucocorticoid concentrations in red-winged blackbirds ( Agelaius phoeniceus) that were naturally infected with haemosporidian parasites, and assessed changes in resistance and tolerance of infection. Glucocorticoid treatment increased burdens of Plasmodium, the parasite causing avian malaria, but only in the absence of co-infection with another Haemosporidian, Haemoproteus. Thus, glucocorticoids might reduce resistance to infection, but co-infection can mitigate the negative consequences of increased hormone concentrations. Glucocorticoid treatment also decreased tolerance of infection. We found no evidence that the inflammatory immune response or rate of red blood cell production underlie the effects of glucocorticoids on resistance and tolerance. Our findings suggest that exogenous glucocorticoids can increase the costs of haemosporidian infections by both increasing parasite numbers and reducing an individual's ability to cope with infection. These effects could scale up to impact populations of both host and parasite.
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http://dx.doi.org/10.1098/rspb.2018.2913DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6501696PMC
April 2019

Environmental stresses induce karyotypic instability in colorectal cancer cells.

Mol Biol Cell 2019 01 31;30(1):42-55. Epub 2018 Oct 31.

Institute of Medical Biology, Singapore 138648, Republic of Singapore.

Understanding how cells acquire genetic mutations is a fundamental biological question with implications for many different areas of biomedical research, ranging from tumor evolution to drug resistance. While karyotypic heterogeneity is a hallmark of cancer cells, few mutations causing chromosome instability have been identified in cancer genomes, suggesting a nongenetic origin of this phenomenon. We found that in vitro exposure of karyotypically stable human colorectal cancer cell lines to environmental stress conditions triggered a wide variety of chromosomal changes and karyotypic heterogeneity. At the molecular level, hyperthermia induced polyploidization by perturbing centrosome function, preventing chromosome segregation, and attenuating the spindle assembly checkpoint. The combination of these effects resulted in mitotic exit without chromosome segregation. Finally, heat-induced tetraploid cells were on the average more resistant to chemotherapeutic agents. Our studies suggest that environmental perturbations promote karyotypic heterogeneity and could contribute to the emergence of drug resistance.
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http://dx.doi.org/10.1091/mbc.E18-10-0626DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6337910PMC
January 2019

Chromosome Segregation: The Bigger They Come, the Harder They Fall.

Curr Biol 2018 06;28(11):R665-R667

Department of Biological Sciences and Biocomplexity Institute, Virginia Tech, Blacksburg, VA, 24061, USA. Electronic address:

Aneuploidy is frequently found to affect individual chromosomes differentially, but it is unclear whether this depends on inter-chromosome differences in missegregation rates. A new study presents evidence that, in the Indian muntjac, centromere-kinetochore size influences the rate at which chromosomes missegregate.
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http://dx.doi.org/10.1016/j.cub.2018.04.036DOI Listing
June 2018

Fluid shear stress impacts ovarian cancer cell viability, subcellular organization, and promotes genomic instability.

PLoS One 2018 22;13(3):e0194170. Epub 2018 Mar 22.

School of Biomedical Engineering and Sciences, Virginia Tech - Wake Forest University, Blacksburg, VA, United States of America.

Ovarian cancer cells are exposed to physical stress in the peritoneal cavity during both tumor growth and dissemination. Ascites build-up in metastatic ovarian cancer further increases the exposure to fluid shear stress. Here, we used a murine, in vitro ovarian cancer progression model in parallel with immortalized human cells to investigate how ovarian cancer cells of increasing aggressiveness respond to [Formula: see text] of fluid-induced shear stress. This biophysical stimulus significantly reduced cell viability in all cells exposed, independent of disease stage. Fluid shear stress induced spheroid formation and altered cytoskeleton organization in more tumorigenic cell lines. While benign ovarian cells appeared to survive in higher numbers under the influence of fluid shear stress, they exhibited severe morphological changes and chromosomal instability. These results suggest that exposure of benign cells to low magnitude fluid shear stress can induce phenotypic changes that are associated with transformation and ovarian cancer progression. Moreover, exposure of tumorigenic cells to fluid shear stress enhanced anchorage-independent survival, suggesting a role in promoting invasion and metastasis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194170PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864000PMC
July 2018

Near-tetraploid cancer cells show chromosome instability triggered by replication stress and exhibit enhanced invasiveness.

FASEB J 2018 07 8;32(7):3502-3517. Epub 2018 Feb 8.

Gastrointestinal and Pancreatic Oncology Group, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Hospital Clínic de Barcelona, Barcelona, Spain.

A considerable proportion of tumors exhibit aneuploid karyotypes, likely resulting from the progressive loss of chromosomes after whole-genome duplication. Here, by using isogenic diploid and near-tetraploid (4N) single-cell-derived clones from the same parental cell lines, we aimed at exploring how polyploidization affects cellular functions and how tetraploidy generates chromosome instability. Gene expression profiling in 4N clones revealed a significant enrichment of transcripts involved in cell cycle and DNA replication. Increased levels of replication stress in 4N cells resulted in DNA damage, impaired proliferation caused by a cell cycle delay during S phase, and higher sensitivity to S phase checkpoint inhibitors. In fact, increased levels of replication stress were also observed in nontransformed, proliferative posttetraploid RPE1 cells. Additionally, replication stress promoted higher levels of intercellular genomic heterogeneity and ongoing genomic instability, which could be explained by high rates of mitotic defects, and was alleviated by the supplementation of exogenous nucleosides. Finally, our data found that 4N cancer cells displayed increased migratory and invasive capacity, both in vitro and in primary colorectal tumors, indicating that tetraploidy can promote aggressive cancer cell behavior.-Wangsa, D., Quintanilla, I., Torabi, K., Vila-Casadesús, M., Ercilla, A., Klus, G., Yuce, Z., Galofré, C., Cuatrecasas, M., Lozano, J. J., Agell, N., Cimini, D., Castells, A., Ried, T., Camps, J. Near-tetraploid cancer cells show chromosome instability triggered by replication stress and exhibit enhanced invasiveness.
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http://dx.doi.org/10.1096/fj.201700247RRDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5998968PMC
July 2018

A guide to classifying mitotic stages and mitotic defects in fixed cells.

Chromosoma 2018 06 6;127(2):215-227. Epub 2018 Feb 6.

Department of Biological Sciences and Biocomplexity Institute, Virginia Tech, 1015 Life Science Circle, Blacksburg, VA, 24061, USA.

Cell division is fundamental to life and its perturbation can disrupt organismal development, alter tissue homeostasis, and cause disease. Analysis of mitotic abnormalities provides insight into how certain perturbations affect the fidelity of cell division and how specific cellular structures, molecules, and enzymatic activities contribute to the accuracy of this process. However, accurate classification of mitotic defects is instrumental for correct interpretation of data and formulation of new hypotheses. In this article, we provide guidelines for identifying specific mitotic stages and for classifying normal and deviant mitotic phenotypes. We hope this will clarify confusion about how certain defects are classified and help investigators avoid misnomers, misclassification, and/or misinterpretation, thus leading to a unified and standardized system to classify mitotic defects.
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http://dx.doi.org/10.1007/s00412-018-0660-2DOI Listing
June 2018

Transient ALT activation protects human primary cells from chromosome instability induced by low chronic oxidative stress.

Sci Rep 2017 02 27;7:43309. Epub 2017 Feb 27.

Department of Science, University Roma Tre, V. le G. Marconi, 446, 00146, Rome, Italy.

Cells are often subjected to the effect of reactive oxygen species (ROS) as a result of both intracellular metabolism and exposure to exogenous factors. ROS-dependent oxidative stress can induce 8-oxodG within the GGG triplet found in the G-rich human telomeric sequence (TTAGGG), making telomeres highly susceptible to ROS-induced oxidative damage. Telomeres are nucleoprotein complexes that protect the ends of linear chromosomes and their dysfunction is believed to affect a wide range of cellular and/or organismal processes. Acute oxidative stress was shown to affect telomere integrity, but how prolonged low level oxidative stress, which may be more physiologically relevant, affects telomeres is still poorly investigated. Here, we explored this issue by chronically exposing human primary fibroblasts to a low dose of hydrogen peroxide. We observed fluctuating changes in telomere length and fluctuations in the rates of chromosome instability phenotypes, such that when telomeres shortened, chromosome instability increased and when telomeres lengthened, chromosome instability decreased. We found that telomere length fluctuation is associated with transient activation of an alternative lengthening of telomere (ALT) pathway, but found no evidence of cell death, impaired proliferation, or cell cycle arrest, suggesting that ALT activation may prevent oxidative damage from reaching levels that threaten cell survival.
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http://dx.doi.org/10.1038/srep43309DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5327399PMC
February 2017

Using Photoactivatable GFP to Study Microtubule Dynamics and Chromosome Segregation.

Methods Mol Biol 2016 ;1413:15-31

Department of Biological Sciences, Biocomplexity Institute, Virginia Tech, 1015 Life Science Circle, Blacksburg, VA, 24061, USA.

Mitosis is a highly dynamic process during which the genetic material is equally distributed between two daughter cells. During mitosis, the sister chromatids of replicated chromosomes interact with dynamic microtubules and such interactions lead to stereotypical chromosome movements that eventually result in chromosome segregation and successful cell division. Approaches that allow quantification of microtubule dynamics and chromosome movements are of utmost importance for a mechanistic understanding of mitosis. In this chapter, we describe methods based on activation of photoactivatable green fluorescent protein (PA-GFP) that can be used for quantitative studies of microtubule dynamics and chromosome segregation.
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http://dx.doi.org/10.1007/978-1-4939-3542-0_2DOI Listing
December 2017

Laser microsurgery reveals conserved viscoelastic behavior of the kinetochore.

J Cell Biol 2016 Mar 21;212(7):767-76. Epub 2016 Mar 21.

Max F. Perutz Laboratories, Department of Chromosome Biology, University of Vienna, 1030 Vienna, Austria

Accurate chromosome segregation depends on proper kinetochore-microtubule attachment. Upon microtubule interaction, kinetochores are subjected to forces generated by the microtubules. In this work, we used laser ablation to sever microtubules attached to a merotelic kinetochore, which is laterally stretched by opposing pulling forces exerted by microtubules, and inferred the mechanical response of the kinetochore from its length change. In both mammalian PtK1 cells and in the fission yeast Schizosaccharomyces pombe, kinetochores shortened after microtubule severing. Interestingly, the inner kinetochore-centromere relaxed faster than the outer kinetochore. Whereas in fission yeast all kinetochores relaxed to a similar length, in PtK1 cells the more stretched kinetochores remained more stretched. Simple models suggest that these differences arise because the mechanical structure of the mammalian kinetochore is more complex. Our study establishes merotelic kinetochores as an experimental model for studying the mechanical response of the kinetochore in live cells and reveals a viscoelastic behavior of the kinetochore that is conserved in yeast and mammalian cells.
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http://dx.doi.org/10.1083/jcb.201506011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4810299PMC
March 2016

Selective advantage of trisomic human cells cultured in non-standard conditions.

Sci Rep 2016 Mar 9;6:22828. Epub 2016 Mar 9.

Department of Biological Sciences, Blacksburg, VA 24061 - USA.

An abnormal chromosome number, a condition known as aneuploidy, is a ubiquitous feature of cancer cells. A number of studies have shown that aneuploidy impairs cellular fitness. However, there is also evidence that aneuploidy can arise in response to specific challenges and can confer a selective advantage under certain environmental stresses. Cancer cells are likely exposed to a number of challenging conditions arising within the tumor microenvironment. To investigate whether aneuploidy may confer a selective advantage to cancer cells, we employed a controlled experimental system. We used the diploid, colorectal cancer cell line DLD1 and two DLD1-derived cell lines carrying single-chromosome aneuploidies to assess a number of cancer cell properties. Such properties, which included rates of proliferation and apoptosis, anchorage-independent growth, and invasiveness, were assessed both under standard culture conditions and under conditions of stress (i.e., serum starvation, drug treatment, hypoxia). Similar experiments were performed in diploid vs. aneuploid non-transformed human primary cells. Overall, our data show that aneuploidy can confer selective advantage to human cells cultured under non-standard conditions. These findings indicate that aneuploidy can increase the adaptability of cells, even those, such as cancer cells, that are already characterized by increased proliferative capacity and aggressive tumorigenic phenotypes.
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http://dx.doi.org/10.1038/srep22828DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783771PMC
March 2016

Consequences of aneuploidy in sickness and in health.

Curr Opin Cell Biol 2016 06 23;40:41-46. Epub 2016 Feb 23.

Department of Biological Sciences and Biocomplexity Institute, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address:

A link between aneuploidy and miscarriage or cancer in humans has been known for a long time. However, only in recent years the development of experimental models of whole-chromosome aneuploidy has allowed investigators to take a closer look at how aneuploidy affects individual cells. Collectively, recent studies using these models have shown that aneuploidy induces transcriptomic and proteomic changes, chromosomal instability, and adaptation. In this article, we discuss the findings from these recent studies and present current and emerging models on how aneuploidy may be deleterious in certain contexts, but beneficial in others.
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http://dx.doi.org/10.1016/j.ceb.2016.02.003DOI Listing
June 2016

Chromosome Bridges Maintain Kinetochore-Microtubule Attachment throughout Mitosis and Rarely Break during Anaphase.

PLoS One 2016 19;11(1):e0147420. Epub 2016 Jan 19.

Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States of America.

Accurate chromosome segregation during cell division is essential to maintain genome stability, and chromosome segregation errors are causally linked to genetic disorders and cancer. An anaphase chromosome bridge is a particular chromosome segregation error observed in cells that enter mitosis with fused chromosomes/sister chromatids. The widely accepted Breakage/Fusion/Bridge cycle model proposes that anaphase chromosome bridges break during mitosis to generate chromosome ends that will fuse during the following cell cycle, thus forming new bridges that will break, and so on. However, various studies have also shown a link between chromosome bridges and aneuploidy and/or polyploidy. In this study, we investigated the behavior and properties of chromosome bridges during mitosis, with the idea to gain insight into the potential mechanism underlying chromosome bridge-induced aneuploidy. We find that only a small number of chromosome bridges break during anaphase, whereas the rest persist through mitosis into the subsequent cell cycle. We also find that the microtubule bundles (k-fibers) bound to bridge kinetochores are not prone to breakage/detachment, thus supporting the conclusion that k-fiber detachment is not the cause of chromosome bridge-induced aneuploidy. Instead, our data suggest that while the microtubules bound to the kinetochores of normally segregating chromosomes shorten substantially during anaphase, the k-fibers bound to bridge kinetochores shorten only slightly, and may even lengthen, during anaphase. This causes some of the bridge kinetochores/chromosomes to lag behind in a position that is proximal to the cell/spindle equator and may cause the bridged chromosomes to be segregated into the same daughter nucleus or to form a micronucleus.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0147420PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4718638PMC
August 2016

Overlap microtubules link sister k-fibres and balance the forces on bi-oriented kinetochores.

Nat Commun 2016 Jan 5;7:10298. Epub 2016 Jan 5.

Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.

During metaphase, forces on kinetochores are exerted by k-fibres, bundles of microtubules that end at the kinetochore. Interestingly, non-kinetochore microtubules have been observed between sister kinetochores, but their function is unknown. Here we show by laser-cutting of a k-fibre in HeLa and PtK1 cells that a bundle of non-kinetochore microtubules, which we term 'bridging fibre', bridges sister k-fibres and balances the interkinetochore tension. We found PRC1 and EB3 in the bridging fibre, suggesting that it consists of antiparallel dynamic microtubules. By using a theoretical model that includes a bridging fibre, we show that the forces at the pole and at the kinetochore depend on the bridging fibre thickness. Moreover, our theory and experiments show larger relaxation of the interkinetochore distance for cuts closer to kinetochores. We conclude that the bridging fibre, by linking sister k-fibres, withstands the tension between sister kinetochores and enables the spindle to obtain a curved shape.
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http://dx.doi.org/10.1038/ncomms10298DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728446PMC
January 2016

The centrosome: a multifaceted cellular weapon against chromosome instability.

Chromosome Res 2016 Jan;24(1):1-4

Department of Biological Sciences and Biocomplexity Institute, Virginia Tech, 1015 Life Science Circle, Blacksburg, VA, 24061, USA.

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http://dx.doi.org/10.1007/s10577-015-9512-6DOI Listing
January 2016

Aurora A Kinase Contributes to a Pole-Based Error Correction Pathway.

Curr Biol 2015 Jul 9;25(14):1842-51. Epub 2015 Jul 9.

Biology Department, University of Massachusetts Amherst, Amherst, MA 01003, USA; Molecular and Cellular Biology Graduate Program, University of Massachusetts Amherst, Amherst, MA 01003, USA. Electronic address:

Chromosome biorientation, where sister kinetochores attach to microtubules (MTs) from opposing spindle poles, is the configuration that best ensures equal partitioning of the genome during cell division. Erroneous kinetochore-MT attachments are commonplace but are often corrected prior to anaphase. Error correction, thought to be mediated primarily by the centromere-enriched Aurora B kinase (ABK), typically occurs near spindle poles; however, the relevance of this locale is unclear. Furthermore, polar ejection forces (PEFs), highest near poles, can stabilize improper attachments by pushing mal-oriented chromosome arms away from spindle poles. Hence, there is a conundrum: erroneous kinetochore-MT attachments are weakened where PEFs are most likely to strengthen them. Here, we report that Aurora A kinase (AAK) opposes the stabilizing effect of PEFs. AAK activity contributes to phosphorylation of kinetochore substrates near poles and its inhibition results in chromosome misalignment and an increased incidence of erroneous kinetochore-MT attachments. Furthermore, AAK directly phosphorylates a site in the N-terminal tail of Ndc80/Hec1 that has been implicated in reducing the affinity of the Ndc80 complex for MTs when phosphorylated. We propose that an AAK activity gradient contributes to correcting mal-oriented kinetochore-MT attachments in the vicinity of spindle poles.
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http://dx.doi.org/10.1016/j.cub.2015.06.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4509859PMC
July 2015

Characterization of Conventional One-Step Sodium Thiosulfate Facilitated Gold Nanoparticle Synthesis.

Nanoscale Res Lett 2015 Dec 28;10(1):940. Epub 2015 May 28.

Department of Biological Systems Engineering, Virginia Tech, Seitz Hall, Blacksburg, VA, 24061, USA,

Gold-gold sulfide nanoparticles are of interest for drug delivery, biomedical imaging, and photothermal therapy applications due to a facile synthesis method resulting in small particles with high near-infrared (NIR) absorption efficiency. Previous studies suggest that the NIR sensitivity of these nanoparticles was due to hexagonally shaped metal-coated dielectric nanoparticles that consist of a gold sulfide core and gold shell. Here, we illustrate that the conventional synthesis procedure results in the formation of polydisperse samples of icosahedral gold particles, gold nanoplates, and small gold spheres. Importantly, through compositional analysis, via UV/vis absorption spectrophotometry, transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDS), we show that all of the nanoparticles exhibit identical face center cubic (FCC) gold crystalline structures, thus suggesting that sulfide is not present in the final fabricated nanoparticles. We show that icosahedrally shaped nanoparticles result in a blue-shifted absorbance, with a peak in the visible range. Alternatively, the nanoplate nanoparticles result in the characteristic NIR absorbance peak. Thus, we report that the NIR-contributing species in conventional gold-gold sulfide formulations are nanoplates that are comprised entirely of gold. Furthermore, polydisperse gold nanoparticle samples produced by the traditional one-step reduction of HAuCl4 by sodium thiosulfate show increased in vitro toxicity, compared to isolated and more homogeneous constituent samples. This result exemplifies the importance of developing monodisperse nanoparticle formulations that are well characterized in order to expedite the development of clinically beneficial nanomaterials.
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http://dx.doi.org/10.1186/s11671-015-0940-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4456593PMC
December 2015

Chromosome mis-segregation and cytokinesis failure in trisomic human cells.

Elife 2015 May 5;4. Epub 2015 May 5.

Department of Biological Sciences, Virginia Tech, Blacksburg, United States.

Cancer cells display aneuploid karyotypes and typically mis-segregate chromosomes at high rates, a phenotype referred to as chromosomal instability (CIN). To test the effects of aneuploidy on chromosome segregation and other mitotic phenotypes we used the colorectal cancer cell line DLD1 (2n = 46) and two variants with trisomy 7 or 13 (DLD1+7 and DLD1+13), as well as euploid and trisomy 13 amniocytes (AF and AF+13). We found that trisomic cells displayed higher rates of chromosome mis-segregation compared to their euploid counterparts. Furthermore, cells with trisomy 13 displayed a distinctive cytokinesis failure phenotype. We showed that up-regulation of SPG20 expression, brought about by trisomy 13 in DLD1+13 and AF+13 cells, is sufficient for the cytokinesis failure phenotype. Overall, our study shows that aneuploidy can induce chromosome mis-segregation. Moreover, we identified a trisomy 13-specific mitotic phenotype that is driven by up-regulation of a gene encoded on the aneuploid chromosome.
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http://dx.doi.org/10.7554/eLife.05068DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4443816PMC
May 2015

Genomic instability: Crossing pathways at the origin of structural and numerical chromosome changes.

Environ Mol Mutagen 2015 Aug 18;56(7):563-80. Epub 2015 Mar 18.

IBPM, Institute of Molecular Biology and Pathology, CNR, Rome, Italy.

Genomic instability leads to a wide spectrum of genetic changes, including single nucleotide mutations, structural chromosome alterations, and numerical chromosome changes. The accepted view on how these events are generated predicts that separate cellular mechanisms and genetic events explain the occurrence of these types of genetic variation. Recently, new findings have shed light on the complexity of the mechanisms leading to structural and numerical chromosome aberrations, their intertwining pathways, and their dynamic evolution, in somatic as well as in germ cells. In this review, we present a critical analysis of these recent discoveries in this area, with the aim to contribute to a deeper knowledge of the molecular networks leading to adverse outcomes in humans following exposure to environmental factors. The review illustrates how several technological advances, including DNA sequencing methods, bioinformatics, and live-cell imaging approaches, have contributed to produce a renewed concept of the mechanisms causing genomic instability. Special attention is also given to the specific pathways causing genomic instability in mammalian germ cells. Remarkably, the same scenario emerged from some pioneering studies published in the 1980s to 1990s, when the evolution of polyploidy, the chromosomal effects of spindle poisons, the fate of micronuclei, were intuitively proposed to share mechanisms and pathways. Thus, an old working hypothesis has eventually found proper validation.
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http://dx.doi.org/10.1002/em.21945DOI Listing
August 2015

Link between aneuploidy and chromosome instability.

Int Rev Cell Mol Biol 2015 7;315:299-317. Epub 2015 Feb 7.

Department of Biological Sciences and Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA, USA.

Aneuploidy is widely acknowledged as a leading cause of miscarriage and birth defects in humans, and is generally known to be deleterious to the survival of individual cells. However, aneuploidy is also ubiquitous in cancer and is found to arise as an adaptive response in certain contexts. This dichotomy of aneuploidy has attracted the interest of researchers for over a century, but many studies have reached conflicting conclusions. The emergence of new technology has allowed scientists to revisit the aneuploidy problem and has fueled a number of recent studies aimed at understanding the effects of aneuploidy on cell physiology. Here, we review these studies, in light of previous observations and knowledge, specifically focusing on the effects of aneuploidy on cellular homeostasis, chromosome stability, and adaptation.
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http://dx.doi.org/10.1016/bs.ircmb.2014.11.002DOI Listing
November 2015

Modelling chromosome dynamics in mitosis: a historical perspective on models of metaphase and anaphase in eukaryotic cells.

Interface Focus 2014 Jun;4(3):20130073

Department of Biological Sciences and Virginia Bioinformatics Institute , Virginia Tech , Blacksburg, VA 24061 , USA.

Mitosis is the process by which the genome is segregated to form two identical daughter cells during cell division. The process of cell division is essential to the maintenance of every form of life. However, a detailed quantitative understanding of mitosis has been difficult owing to the complexity of the process. Indeed, it has been long recognized that, because of the complexity of the molecules involved, their dynamics and their properties, the mitotic events that mediate the segregation of the genome into daughter nuclei cannot be fully understood without the contribution of mathematical/quantitative modelling. Here, we provide an overview of mitosis and describe the dynamic and mechanical properties of the mitotic apparatus. We then discuss several quantitative models that emerged in the past decades and made an impact on our understanding of specific aspects of mitosis, including the motility of the chromosomes within the mitotic spindle during metaphase and anaphase, the maintenance of spindle length during metaphase and the switch to spindle elongation that occurs during anaphase.
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http://dx.doi.org/10.1098/rsfs.2013.0073DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3996585PMC
June 2014

The mitotic origin of chromosomal instability.

Curr Biol 2014 Feb;24(4):R148-9

Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA; Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, USA. Electronic address:

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http://dx.doi.org/10.1016/j.cub.2014.01.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970164PMC
February 2014

Cancer karyotypes: survival of the fittest.

Front Oncol 2013 7;3:148. Epub 2013 Jun 7.

Department of Biological Sciences, Virginia Tech , Blacksburg, VA , USA.

Cancer cells are typically characterized by complex karyotypes including both structural and numerical changes, with aneuploidy being a ubiquitous feature. It is becoming increasingly evident that aneuploidy per se can cause chromosome mis-segregation, which explains the higher rates of chromosome gain/loss observed in aneuploid cancer cells compared to normal diploid cells, a phenotype termed chromosomal instability (CIN). CIN can be caused by various mechanisms and results in extensive karyotypic heterogeneity within a cancer cell population. However, despite such karyotypic heterogeneity, cancer cells also display predominant karyotypic patterns. In this review we discuss the mechanisms of CIN, with particular emphasis on the role of aneuploidy on CIN. Further, we discuss the potential functional role of karyotypic patterns in cancer.
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http://dx.doi.org/10.3389/fonc.2013.00148DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3675379PMC
June 2013

MISP: The missing link between extracellular matrix and astral microtubules.

Cell Cycle 2013 Jun 30;12(12):1821-2. Epub 2013 May 30.

Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, USA.

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http://dx.doi.org/10.4161/cc.25171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3735691PMC
June 2013