10 results on '"Armant, Olivier"'
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2. Ionizing radiation affects the demography and the evolution of Caenorhabditis elegans populations.
- Author
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Quevarec, Loïc, Réale, Denis, Dufourcq-Sekatcheff, Elizabeth, Armant, Olivier, Adam-Guillermin, Christelle, and Bonzom, Jean-Marc
- Subjects
IONIZING radiation ,CAENORHABDITIS elegans ,REPRODUCTION ,ANIMAL clutches ,LIFE history theory ,RADIATION exposure ,DEMOGRAPHY ,DOSE-response relationship (Radiation) ,BROOD parasitism - Abstract
Ionizing radiation can reduce survival, reproduction and affect development, and lead to the extinction of populations if their evolutionary response is insufficient. However, demographic and evolutionary studies on the effects of ionizing radiation are still scarce. Using an experimental evolution approach , we analyzed population growth rate and associated change in life history traits across generations in Caenorhabditis elegans populations exposed to 0, 1.4, and 50.0 mGy.h
−1 of ionizing radiation (gamma external irradiation). We found a higher population growth rate in the 1.4 mGy.h−1 treatment and a lower in the 50.0 mGy.h−1 treatment compared to the control. Realized fecundity was lower in both 1.4 and 50.0 mGy.h−1 than control treatment. High irradiation levels decreased brood size from self-fertilized hermaphrodites, specifically early brood size. Finally, high irradiation levels decreased hatching success compared to the control condition. In reciprocal-transplant experiments, we found that life in low irradiation conditions led to the evolution of higher hatching success and late brood size. These changes could provide better tolerance against ionizing radiation, investing more in self-maintenance than in reproduction. These evolutionary changes were with some costs of adaptation. This study shows that ionizing radiation has both demographic and evolutionary consequences on populations. • Ionizing radiation had both demographic and evolutionary consequences on populations. • Multigenerational radiation exposure led to decreased reproduction and embryo survival. • Populations adapted to radiation through improved embryo survival and a slower life strategy. • Evolutionary changes in irradiated environments were accompanied by adaptive costs. [ABSTRACT FROM AUTHOR]- Published
- 2023
- Full Text
- View/download PDF
3. Transgenerational DNA Methylation Changes in Daphnia magnaExposed to Chronic γ Irradiation
- Author
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Trijau, Marie, Asselman, Jana, Armant, Olivier, Adam-Guillermin, Christelle, De Schamphelaere, Karel A. C., and Alonzo, Frédéric
- Abstract
Our aim was to investigate epigenetic changes in Daphnia magnaafter a 25-day chronic external γ irradiation (generation F0 exposed to 6.5 μGy·h–1or 41.3 mGy·h–1) and their potential inheritance by subsequent recovering generations, namely, F2 (exposed as germline cells in F1 embryos) and F3 (the first truly unexposed generation). Effects on survival, growth, and reproduction were observed and DNA was extracted for whole-genome bisulfite sequencing in all generations. Results showed effects on reproduction in F0 but no effect in the subsequent generations F1, F2, and F3. In contrast, we observed significant methylation changes at specific CpG positions in every generation independent of dose rate, with a majority of hypomethylation. Some of these changes were shared between dose rates and between generations. Associated gene functions included gene families and genes that were previously shown to play roles during exposure to ionizing radiation. Common methylation changes detected between generations F2 and F3 clearly showed that epigenetic modifications can be transmitted to unexposed generations, most likely through the germline, with potential implications for environmental risk.
- Published
- 2018
- Full Text
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4. The Cdx2 homeobox gene suppresses intestinal tumorigenesis through non–cell-autonomous mechanisms
- Author
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Balbinot, Camille, Armant, Olivier, Elarouci, Nabila, Marisa, Laetitia, Martin, Elisabeth, De Clara, Etienne, Onea, Alina, Deschamps, Jacqueline, Beck, Felix, Freund, Jean-Noël, and Duluc, Isabelle
- Abstract
Developmental genes contribute to cancer, as reported for the homeobox gene Cdx2 playing a tumor suppressor role in the gut. In this study, we show that human colon cancers exhibiting the highest reduction in CDX2 expression belong to the serrated subtype with the worst evolution. In mice, mosaic knockout of Cdx2 in the adult intestinal epithelium induces the formation of imperfect gastric-type metaplastic lesions. The metaplastic knockout cells do not spontaneously become tumorigenic. However, they induce profound modifications of the microenvironment that facilitate the tumorigenic evolution of adjacent Cdx2-intact tumor-prone cells at the surface of the lesions through NF-κB activation, induction of inducible nitric oxide synthase, and stochastic loss of function of Apc. This study presents a novel paradigm in that metaplastic cells, generally considered as precancerous, can induce tumorigenesis from neighboring nonmetaplastic cells without themselves becoming cancerous. It unveils the novel property of non–cell-autonomous tumor suppressor gene for the Cdx2 gene in the gut.
- Published
- 2018
- Full Text
- View/download PDF
5. Fine-tuning and autoregulation of the intestinal determinant and tumor suppressor homeobox gene CDX2 by alternative splicing
- Author
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Balbinot, Camille, Vanier, Marie, Armant, Olivier, Nair, Asmaa, Penichon, Julien, Soret, Christine, Martin, Elisabeth, Saandi, Thoueiba, Reimund, Jean-Marie, Deschamps, Jacqueline, Beck, Felix, Domon-Dell, Claire, Gross, Isabelle, Duluc, Isabelle, and Freund, Jean-Noël
- Abstract
On the basis of phylogenetic analyses, we uncovered a variant of the CDX2 homeobox gene, a major regulator of the development and homeostasis of the gut epithelium, also involved in cancer. This variant, miniCDX2, is generated by alternative splicing coupled to alternative translation initiation, and contains the DNA-binding homeodomain but is devoid of transactivation domain. It is predominantly expressed in crypt cells, whereas the CDX2 protein is present in crypt cells but also in differentiated villous cells. Functional studies revealed a dominant-negative effect exerted by miniCDX2 on the transcriptional activity of CDX2, and conversely similar effects regarding several transcription-independent functions of CDX2. In addition, a regulatory role played by the CDX2 and miniCDX2 homeoproteins on their pre-mRNA splicing is displayed, through interactions with splicing factors. Overexpression of miniCDX2 in the duodenal Brunner glands leads to the expansion of the territory of these glands and ultimately to brunneroma. As a whole, this study characterized a new and original variant of the CDX2 homeobox gene. The production of this variant represents not only a novel level of regulation of this gene, but also a novel way to fine-tune its biological activity through the versatile functions exerted by the truncated variant compared to the full-length homeoprotein. This study highlights the relevance of generating protein diversity through alternative splicing in the gut and its diseases.
- Published
- 2017
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6. Loss of function of myosin chaperones triggers Hsf1-mediated transcriptional response in skeletal muscle cells
- Author
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Etard, Christelle, Armant, Olivier, Roostalu, Urmas, Gourain, Victor, Ferg, Marco, and Strähle, Uwe
- Abstract
Mutations in myosin chaperones Unc45b and Hsp90aa1.1 as well as in the Unc45b-binding protein Smyd1b impair formation of myofibrils in skeletal muscle and lead to the accumulation of misfolded myosin. The concomitant transcriptional response involves up-regulation of the three genes encoding these proteins, as well as genes involved in muscle development. The transcriptional up-regulation of unc45b, hsp90aa1.1and smyd1bis specific to zebrafish mutants with myosin folding defects, and is not triggered in other zebrafish myopathy models. By dissecting the promoter of unc45b, we identify a Heat shock factor 1 (Hsf1) binding element as a mediator of unc45bup-regulation in myofibers lacking myosin folding proteins. Loss-of-function of Hsf1 abolishes unc45bup-regulation in mutants with defects in myosin folding. Taken together, our data show that skeletal muscle cells respond to defective myosin chaperones with a complex gene program and suggest that this response is mediated by Hsf1 activation.
- Published
- 2015
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7. The Helix‐Loop‐Helix Protein Id1 Controls Stem Cell Proliferation During Regenerative Neurogenesis in the Adult Zebrafish Telencephalon
- Author
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Viales, Rebecca Rodriguez, Diotel, Nicolas, Ferg, Marco, Armant, Olivier, Eich, Julia, Alunni, Alessandro, März, Martin, Bally-Cuif, Laure, Rastegar, Sepand, and Strähle, Uwe
- Abstract
The teleost brain has the remarkable ability to generate new neurons and to repair injuries during adult life stages. Maintaining life‐long neurogenesis requires careful management of neural stem cell pools. In a genome‐wide expression screen for transcription regulators, the id1gene, encoding a negative regulator of E‐proteins, was found to be upregulated in response to injury. id1expression was mapped to quiescent type I neural stem cells in the adult telencephalic stem cell niche. Gain and loss of id1function in vivo demonstrated that Id1 promotes stem cell quiescence. The increased id1expression observed in neural stem cells in response to injury appeared independent of inflammatory signals, suggesting multiple antagonistic pathways in the regulation of reactive neurogenesis. Together, we propose that Id1 acts to maintain the neural stem cell pool by counteracting neurogenesis‐promoting signals. StemCells2015;33:892–903
- Published
- 2015
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8. Gene Responses in the Central Nervous System of Zebrafish Embryos Exposed to the Neurotoxicant Methyl Mercury.
- Author
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Nga Yu Ho, Lixin Yang, Legradi, Jessica, Armant, Olivier, Takamiya, Masanari, Rastegar, Sepand, and Strähle, Uwe
- Published
- 2013
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9. A systems biology analysis of reproductive toxicity effects induced by multigenerational exposure to ionizing radiation in C. elegans.
- Author
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Guédon, Rémi, Maremonti, Erica, Armant, Olivier, Galas, Simon, Brede, Dag Anders, and Lecomte-Pradines, Catherine
- Subjects
IONIZING radiation ,RADIATION exposure ,SYSTEMS biology ,GAMMA rays ,CAENORHABDITIS elegans ,LIPID metabolism ,GONADS - Abstract
Understanding the effects of chronic exposure to pollutants over generations is of primary importance for the protection of humans and the environment; however, to date, knowledge on the molecular mechanisms underlying multigenerational adverse effects is scarce. We employed a systems biology approach to analyze effects of chronic exposure to gamma radiation at molecular, tissue and individual levels in the nematode Caenorhabditis elegans. Our data show a decrease of 23% in the number of offspring on the first generation F0 and more than 40% in subsequent generations F1, F2 and F3. To unveil the impact on the germline, an in-depth analysis of reproductive processes involved in gametes formation was performed for all four generations. We measured a decrease in the number of mitotic germ cells accompanied by increased cell-cycle arrest in the distal part of the gonad. Further impact on the germline was manifested by decreased sperm quantity and quality. In order to obtain insight in the molecular mechanisms leading to decreased fecundity, gene expression was investigated via whole genome RNA sequencing. The transcriptomic analysis revealed modulation of transcription factors, as well as genes involved in stress response, unfolded protein response, lipid metabolism and reproduction. Furthermore, a drastic increase in the number of differentially expressed genes involved in defense response was measured in the last two generations, suggesting a cumulative stress effect of ionizing radiation exposure. Transcription factor binding site enrichment analysis and the use of transgenic strain identified daf-16/FOXO as a master regulator of genes differentially expressed in response to radiation. The presented data provide new knowledge with respect to the molecular mechanisms involved in reproductive toxic effects and accumulated stress resulting from multigenerational exposure to ionizing radiation. [Display omitted] • Multigenerational exposure to gamma radiation caused reproductive toxicity effects. • Radiation significantly reduced number of mitotic cells as well as quality of sperm. • A progressive transcriptomic stress response is induced by gamma radiation. • DAF-16/FOXO is a central regulator of the transcriptomic stress response. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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10. HeRBi: Helmholtz Repository of Bioparts
- Author
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Strähle, Uwe, Ferg, Marco, Armant, Olivier, Gradl, Marion, Kaufmann, Larissa, and Rastegar, Sepand
- Published
- 2016
- Full Text
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