Résultats de recherche

Sujet de thèse Use of BioID within mitochondria: examples with the study of human mitochondrial co-translational import process and with the identification of MPV17 function Résumé This thesis was divided in two different parts dedicated to the study of a mitochondrial process and of a mitochondrial protein using a proximity labelling assay called BioID.            The first project was dedicated to the study of a poorly characterized process, the mitochondrial co-translational import. In this process, translation is coupled to the translocation of the mitochondrial proteins, alleviating the energy cost typically associated with the post-translational import relying on chaperone systems. However, the mechanisms are still unclear with only few actors identified but none that have been described in mammals yet. We thus profiled endogenously the TOM20 proxisome using BioID. Despite the enrichment of RNA binding proteins in the TOM20 proxisome, we could not demonstrate a role for a selected candidate, LARP4, in the mitochondrial co-translational import process. Nonetheless, additional uses of this BioID cell line were highlighted such as the monitoring of protein entry inside mitochondria and a potential application in the prediction of mitochondrial protein half-life.The second project was dedicated to the study of MPV17, a protein of the inner mitochondrial membrane whose gene is associated with mitochondrial DNA depletion syndrome. However, the exact molecular function of the protein is still unclear. The approach used in this project was to identify the interacting partners of MPV17, using BioID, to get additional clues about the protein function. In this project we demonstrated an interaction of MPV17 with the MICOS complex but the KO of MPV17 didn’t impact mitochondria ultrastructure. However, the depletion of MPV17 protein led to increased mitochondria-derived vesicles formation. Therefore, we investigated a potential degradation of the mtDNA as the cause of the mtDNA depletion observed in MPV17 KO cells but, despite a higher mitophagy level in KO cells, the blockade of the lysosomal activity didn’t prevent the depletion. Additional in silico analyses suggested a channel activity of MPV17 further supported by its direct interaction with the Cyclophilin D, a protein of the mitochondrial permeability transition pore. Interestingly, MPV17 KO cells also display higher level of mitochondrial calcium which would be related to the degradation of the mtDNA since the blockade of mitochondrial calcium entry prevents the depletion. We thus propose a role of MPV17 as a potential new member of the mitochondrial permeability transition pore whereas in the absence of the protein, the build-up of calcium inside the mitochondria would lead to the observed mtDNA degradation. Jury Prof. Benoît MUYLKENS (UNamur), présidentProf. Patsy RENARD (UNamur), promotrice et secrétaireProf. Thierry ARNOULD (UNamur), co-promoteurProf. Dr. David PLA-MARTIN (Heinrich Heine University Düsseldorf, Germany)Dr Timothy WAI (Institut Pasteur de Paris, France)Prof. Guy LENAERS (Université d’Angers, France)Prof. Sven EYCKERMAN (Universiteit Gent)

Résumé : Impact de la voie UPR sur l’établissement du phénotype sénescent induit par les UVB Le vieillissement cutané, influencé par une combinaison de facteurs intrinsèques et extrinsèques, entraine des dommages capables d'altérer les fonctions cutanées. Parmi les facteurs extrinsèques, les rayonnements ultraviolets (UV) sont responsables du photo-vieillissement de la peau. Ces éléments conduisent notamment à une accumulation de cellules sénescentes capables de contribuer au développement de pathologies liées à l’âge, telles que les cancers cutanés. En effet, la sénescence s’accompagne de profonds changements morphologiques et moléculaires au sein de la cellule. Cela inclut notamment une modification de son sécrétome, qui s'enrichit en cytokines pro-inflammatoires, en facteurs de croissance et en enzymes remodelant la matrice extracellulaire, altérants les caractéristiques des tissus lors du vieillissement. Néanmoins, les mécanismes précis qui aboutissent au phénotype sénescent induit par les UVB restent largement inconnus.            Dans ce contexte, l’objectif principal de ce travail a été d'identifier des mécanismes moléculaires sous-jacents à l’établissement de la sénescence induite par les UVB dans des fibroblastes de derme humains normaux (NHDFs), mécanismes qui pourraient contribuer au vieillissement cutané.  In vitro, nous avons confirmé que des expositions répétées aux UVB induisent la sénescence prématurée des NHDFs et que cet état est associé à l’activation des trois branches de la voie UPR (Unfolded Protein Response) responsables du maintien de l’homéostasie du réticulum endoplasmique (RE), le premier compartiment de sécrétion. Ces observations ont été supportées par une analyse transcriptomique, révélant des éléments de régulation liés aux grandes voies de sénescence et aux fonctions du RE dans les NHDFs exposés aux UVB.    Par la suite, nous avons montré que la branche ATF6α joue un rôle central dans la survenue des biomarqueurs du phénotype sénescent induit par les UVB. En effet, l’invalidation d’ATF6α protège non seulement des changements morphologiques induits par les UVB, mais réduit le pourcentage de cellules positives pour la SA-βgalactosidase (SA-βgal), prévient la persistance des dommages à l'ADN, et modifie l'expression de facteurs majeurs du phénotype sécrétoire associé à la sénescence (SASP).    Le SASP exerçant entre autres une action pro-tumorale, nous avons cherché à évaluer si le milieu conditionné (MC) des fibroblastes exposés aux UVB et invalidé pour ATF6α pouvait impacter le potentiel de migration et d'invasion de cellules issues de mélanomes. Cependant, nous n'avons pas observé d’effets pro-migratoires ou pro-invasifs dépendants d’ATF6α.Afin de mettre en évidence un potentiel rôle d’ATF6α dans un autre processus biologique, nous avons exploité nos analyses transcriptomiques et sécrétomiques et avons identifié un possible effet d’ATF6α sur le contrôle paracrine de l’environnement cutané. Pour explorer cela, nous nous sommes concentrés sur les facteurs du SASP (cytokines et métalloprotéases) régulés par ATF6α et dont l’impact sur l’environnement tissulaire était connu. Ensuite, nous avons traité un modèle d'épiderme humain reconstruit (RHE) avec du MC issu de NHDFs exposés aux UVB ou non, et invalidés ou non pour ATF6α. Etonnement, nous avons observés que le MC des NHDFs exposés aux UVB augmente l’épaisseur du RHE ainsi que la prolifération des kératinocytes basaux, via un mécanisme dépendant d’ATF6α. Enfin, nous avons identifié l'IL8 comme un facteur paracrine majeur impliqué dans ce processus, puisque le blocage d’IL-8 par des anticorps neutralisants prévient la prolifération excessive des kératinocytes.            En conclusion, nous rapportons le rôle d’ATF6α dans la sénescence induite par les UVB ainsi que son impact sur la préservation de l'homéostasie cutanée en condition de stress notamment par la régulation de l’expression des composants du SASP. Cela suggère qu'ATF6α et ses effecteurs pourrait être des cibles prometteuses contrôlant les effets du vieillissement cutané.Abstract: Impact of the UPR pathway on the establishment of the senescent phenotype induced by UVBSkin aging, influenced by a combination of intrinsic and extrinsic factors, can result in damage that has the potential to alter skin functions. Among extrinsic factors, ultraviolet (UV) radiation is responsible for skin photoaging. These factors notably contribute to the accumulation of senescent cells which in turn can contribute to the development of age-related pathologies, including skin cancers. Indeed, senescence is characterized by profound morphological and molecular changes within the cell. This includes a modification of its secretome, which becomes enriched in pro-inflammatory cytokines, growth factors, and matrix-remodeling enzymes, altering tissue characteristics during aging. However, the exact mechanisms driving the senescent phenotype induced by UVB remain largely unknown.          In this context, the main objective of this work was to identify the underlying molecular mechanisms responsible for the establishment of UVB-induced senescence in normal human dermal fibroblasts (NHDFs), mechanisms that may play a role in skin aging.   In vitro, we confirmed that repeated exposures to UVB induce premature senescence of NHDFs and that this state is associated with the activation of the three branches of the Unfolded Protein Response (UPR), which are responsible for maintaining endoplasmic reticulum (ER) homeostasis, the primary cellular secretion compartment. These observations were supported by transcriptomic analysis, revealing regulatory elements related to major senescence pathways and ER functions in UVB-exposed NHDFs. Subsequently, we demonstrated that the ATF6α branch plays a central role in the development of the UVB-induced senescent phenotype. Indeed, the silencing of ATF6α not only protects against morphological changes induced by UVB, but also reduces the percentage of senescence-associated β-galactosidase (SA-βgal) positive cells, prevents the persistence of DNA damage, and alters the expression of major factors associated with the senescence-associated secretory phenotype (SASP).The SASP, exerting a pro-tumoral action, led us to assess whether the conditioned medium (CM) from UVB-exposed fibroblasts invalidated for ATF6α could impact the migration and invasion potential of melanoma cells. However, we did not observe any ATF6α-dependent pro-migratory or pro-invasive effects.  To highlight a potential role of ATF6α in another biological process, we further analyzed our transcriptomic and secretomic analyses and identified a possible effect of ATF6α on the paracrine control of the skin environment. To explore this, we focused on SASP factors (cytokines and metalloproteinases) regulated by ATF6α and whose impact on tissue environment was known. Subsequently, we treated a reconstructed human epidermis (RHE) model with CM from NHDFs exposed or not to UVB and invalidated or not for ATF6α. Surprisingly, we observed that the CM from UVB-exposed NHDFs increased the thickness of the RHE as well as the proliferation of basal keratinocytes, via an ATF6α-dependent mechanism. Finally, we identified IL8 as a major paracrine factor involved in this process, as blocking IL-8 with neutralizing antibodies prevented excessive proliferation of keratinocytes.  In conclusion, we report the role of ATF6α in UVB-induced senescence and its impact on the preservation of skin homeostasis under stress conditions, particularly through the regulation of the expression of SASP components. This suggests that ATF6α and its effectors could be promising targets for controlling the effects of skin aging. Jury Prof. Yves POUMAY (Département de Médecine, UNamur), présidentProf. Florence CHAINIAUX (Département de Biologie, UNamur), promotrice et secrétaireProf. Olivier PLUQUET (Canther, Université de Lille), co-promoteurProf. Isabelle PETROPULOS (Adaptation Biologique et Vieillissement, Sorbonne Université)Prof. Jérôme LAMARTINE (Laboratoire de Biologie Tissulaire et d’Ingénierie thérapeutique, Université Claude Bernard Lyon 1)Prof. Fabienne FOUFELLE (Maladies métaboliques, diabète et comorbidités, Sorbonne Université)

Thèse de doctorat en sciences biologiques Résumé Nanotechnology is one of the most important fields of innovation in the 21st century. Engineered nanoparticles are used in a wide range of products and industries such as cosmetics, electronics, food packaging, textiles, and even medicine. However, the rapid development of these new materials comes with the challenge of accurately assessing the risks they may pose to human health and the environment. Once released into aquatic ecosystems, nanoparticles are expected to interact with other co-occurring pollutants, including other nanoparticles. However, the effects resulting from exposure to mixtures of nanomaterials on aquatic organisms are rarely known.In this context, the present thesis aimed to assess the effects of exposure to two of the most widely used nanoparticles, zinc oxide (ZnO) and titanium dioxide (TiO2), separately and in a mixture, using a model fish species, the rainbow trout (Oncorhynchus mykiss). Different approaches were developed to achieve this goal. First, an in vitro model was used to highlight the differences in behavior and toxicity between the individual nanoparticles and their mixture. Rainbow trout were then exposed to environmentally realistic concentrations of the two nanoparticles individually and their mixture. In the first place, the gill's innate immunity and its associated microbiota were studied as they represent the first line of defense of the organism's immune systems, but also because gills represent one of the routes of entrance for nanoparticles in the organism. A stress-on-stress approach was also employed. The trout were challenged with a pathogenic bacterium following the exposure to the nanomaterials to assess their effect on the immunocompetence of the fish.Through this multifaceted approach, this thesis helped provide new insights into the behavior of nanoparticle mixtures and their potential for toxicity. Our findings show that exposure to nanoparticles, usually regarded as having low toxicity potential such as TiO2, may induce toxicological effects when interacting with other nanoparticles. Jury Prof. Frédéric SILVESTRE (UNamur), présidentProf. Patrick KESTEMONT (UNamur), promoteur et secrétaireDr Valérie CORNET (UNamur)Prof. Joachim STURVE (University of Gothenburg)Prof. Catherine MOUNEYRAC (Université Catholique de l’Ouest)Prof. Mutien-Marie GARIGLIANI (Université de Liège)

Un drink sera organisé suite à la conférence.Cette conférence est proposée par "Kàp to UNIVERSEH", le projet sans kot de vulgarisation spatiale de l'Université de Namur, et Local Student Club d'UNIVERSEH.Quand : mercredi 26 février 2025 à 19hOù : Faculté des Sciences - Auditoire S01Gratuit Je m'inscris

Infos pratiques Date : Mercredi 12 mars 2025Lieu : PA01, l’entrée se fera par le hall de la faculté des sciences18h45 : Ouverture des portes19h15 : Début du spectaclePrix et vente des places : 5 € en prévente / 7 € le jour mêmeVente : Sur le temps de midi toute la semaine du 3 mars dans le hall de la fac !Paiement : Nous privilégions le liquide, mais nous acceptons également les paiements par code QR ou virement. En savoir plus

Le GIEC alerte sur l’impact croissant du réchauffement climatique sur l’eau, avec des sécheresses et inondations plus fréquentes, menaçant l’approvisionnement mondial. D’ici 2050, 42 % des bassins hydrographiques seront gravement affectés, et les dégâts liés aux inondations pourraient quadrupler en cas de réchauffement de 4 °C. Les populations les plus vulnérables, bien que peu responsables, en subissent les pires conséquences. En Wallonie, les récentes catastrophes climatiques et pollutions de l’eau illustrent ces enjeux. Pour sensibiliser le public, un événement est organisé à Charleroi avec débats et projections.Au programme17h00 | Séance d'introduction           Responsable UNESCO Belgique           Mr Aurélien Dumont, Secrétariat du Programme hydrologique intergouvernemental de l’UNESCO, Situation Mondiale de l’eau17h40 | Projection du film "H2O, l’eau, la vie et nous : l’Urgence"18h30 | Pause18h45 | Conférences et débat           Prof. Marnik Vanclooster (UCLouvain), « Situation en Wallonnie »           Prof. Alfred Bernard (UCLouvain), « Normes et toxicologie »           Débat Animé par le Prof. Karim ZouaouiBoudjeltia (ULB), avec la participation d’Aurélien Dumont, Marnik Vanclooster, Alfred Bernard.20h30 | Cocktail dinatoireGRATUIT : Inscription souhaitée : f.amer@wbi.beLes membres de la Sous-Commission « sciences exactes et naturelles »Bernard Feltz (UCLouvain, Président), Bertrand Hespel (UNamur), Marie-Geneviève Pinsart (ULB, CIGB), René Rezsohazy (UCLouvain), Frédéric Rychter (Secrétaire général), Olivier Sartenaer (UNamur), Didier Serteyn (ULiège), Anne Staquet (UMons), Marnik Vanclooster (UCLouvain), Karim Zouaoui Boudjeltia (ULB)

Programme 18:00 – 18:30: Formation à la cartographie18:30 – 21:00 : CartographiePizza et drink offertsIl y aura plusieurs PC à disposition mais amenez si possible votre PC portable et votre souris!Pour s'inscrire, c'est ici : https://www.eventbrite.be/e/belgian-interuniversity-mapathon-2025-tickets-1277481905769?aff=oddtdtcreator

La conférence parlera des origines de l'eau, des raisons de sa stabilité, mais aussi, paradoxalement, de sa très grande réactivité qui permet la vie telle que nous la connaissons. Ces notions fondamentales de chimie seront ponctuellement illustrées par des expériences parfois décoiffantes.La conférence sera suivie d'un drink.

Une conférence donnée en anglais par André Füzfa, Professeur au sein du Département de Mathématique de l'UNamur. Quand : Lundi 14 avril 2025 à 19hOù : Université de Namur - Faculté des sciences - Amphithéâtre S01GratuitEn anglaisPossibilité de rejoindre la conférence en ligne, le lien sera partagé quelques heures avant l'évènement. Retrouvez toutes les infos sur les comptes Facebook (Kapto.UNIVERSEH.) et Instagram (@kapto_universeh) du Kot-à-projet. Un drink sera organisé suite à la conférence.Cette conférence est proposée par "Kàp to UNIVERSEH", le projet sans kot de vulgarisation spatiale de l'Université de Namur, et Local Student Club d'UNIVERSEH. S'inscrire

2025 theme: Stress and emotions in animals The purpose of the symposium aligns with the missions of BCLAS to promote the replacement, reduction and refinement of laboratory animal use by driving reflection, sharing information, providing education and support to the scientific community, authorities and public, in order to lead to an ethical, responsible and qualitative research enabling further improvement in human & animal health.

Abstract Over the past two centuries, advances in healthcare have significantly extended life expectancy by reducing the impact of many diseases. As this progress continues, attention shifts toward more complex illnesses, with cancer emerging as the foremost challenge. Photodynamic therapy (PDT) is a light-activated cancer treatment approved in 1995 that offers a targeted approach by using photosensitizers (PSs) — compounds that, upon light activation, generate reactive singlet oxygen to selectively damage tumor tissue. However, current commercial PSs suffer from several drawbacks: ill-defined composition, poor accumulation in tumors and slow clearance, limited application depths, and insufficient fluorescence for diagnostic imaging. This thesis addresses these limitations by pursuing the development of efficient and partially fluorescent PSs that absorb strongly in the red to near-infrared (NIR) range. The first part of the work focuses on computational tools based on quantum chemistry, particularly density functional theory, to predict molecular properties relevant to PDT. These methods are benchmarked and refined to ensure accurate and efficient screening of candidate compounds. Additionally, a commonly used metric for quantifying charge transfer distance in excited states is reformulated to be independent of molecular symmetry, allowing broader and more robust applicability. In the second part, these tools guide the design of novel PSs. One strategy involves modifying pyrrolopyrrole aza-BODIPY dyes into donor–acceptor structures to enable singlet oxygen generation via spin–orbit charge transfer intersystem crossing (SOCT-ISC). Another approach focuses on a twisted BODIPY compound that achieves photosensitization by facilitating ISC through a distortion of the symmetry. This PS is tuned to absorb NIR light and, in some cases, leverage the SOCT-ISC mechanism. Overall, these efforts did not only yield promising PSs but also provided computational insights to accelerate future developments in the field. Le jury Prof. Guillaume BERIONNI (UNamur), PrésidentProf. Benoît CHAMPAGNE (UNamur), SecrétaireProf. Wouter MAES (UHasselt)Prof. Dirk VANDERZANDE (UHasselt)Prof. Anitha ETHIRAJAN (UHasselt)Prof. Yoann OLIVIER (UNamur)Prof. Wim DEHAEN (KULeuven)Prof. Anna PAINELLI (Universita di Parma)Prof. Mariangela DI DONATO (LENS)Prof. Jan COLPAERT (UHasselt)

Charting the DNA methylome landscape in cancer, chronic disease and phenotype Abstract: Our team has developed some of the first pipelines for genome-scale DNA methylation analysis. Our work has revealed aberrant methylation and expression patterns in several cancer types and revealed new mechanism of epigenetic regulation in cancer cells. We are now applying cutting-edge whole genome scale DNA methylation analysis in tissues as well as well as in cell free DNA (epigenetic liquid biopsy) and epigenetic editing platforms to investigate clinically relevant biomedical questions in cancer (for example, methylation map of colorectal, prostate, lung cancer and pancreatic cancer patients). Our work in epigenetic editing has implication in revealing causal function and new epigenetic regulation. In this talk, I will present the key findings from some of our works over the years and also elaborate on some recent and future directions in understanding the role of DNA methylation events in cancer metastasis, early detection, and treatment monitoring in solid cancers and also in chronic diseases and phenotype. More information on the ILEE website