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Institut de biologie Valrose

Works: 72 works in 72 publications in 2 languages and 72 library holdings
Roles: Other
Publication Timeline
Most widely held works by Institut de biologie Valrose
Rôle du récepteur Sigma-1 sur la régulation des canaux ioniques impliqués dans la carcinogenèse by David Crottès( )

1 edition published in 2014 in French and held by 1 WorldCat member library worldwide

The sigma-1 receptor is a chaperone protein active in damaged tissues. The sigma-1 receptor is mainly expressed into brain and have a neuroprotective role in ischemia and neurodegenerative diseases. The sigma-1 receptor is also expressed into cancer cell lines and recent investigations suggest its involvement into proliferation and apoptosis. However, its role in carcinogenesis remains to delineating. Ion channels are involved in numerous physiological processes (heart beating, nervous influx, ...). These membrane proteins currently emerge as a new class of therapeutic targets in cancer. During my thesis, I observed that the sigma-1 receptor regulates voltage-dependent potassium channel hERG and voltage-dependent sodium channel Nav1.5 activities respectively into leukemic and breast cancer cell lines. I also demonstrated that the sigma-1 receptor, through its action on hERG channel, increases leukemia invasiveness by promoting interaction with tumor microenvironment. These results highlight the role of the sigma-1 receptor on cancer cell electrical plasticity and suggest this chaperone protein as a potential therapeutic target to limit tumor progression
Croissance invasive chez un champignon pathogène de l'Homme : forces mécaniques et réorganisation cellulaire by Charles Puerner( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

The dimorphic fungi Candida albicans is a major human pathogen that causes life-threatening infections for immunocompromised patients. I have investigated C. albicans invasive filamentous growth, in collaboration with physicists, in particular the mechanical forces during this process, and quantitated the effects of these forces on cell morphology. Furthermore, I have examined the function of a filament tip cluster of vesicles, known as a Spitzenkörper, in the regulation of growth and cell morphology. Physical forces generated by C. albicans filamentous growth are likely to be critical for host tissue penetration, as well as escape from host immune cells. We have used the polymer polydimethylsiloxane (PDMS) to generate microchambers with different stiffness, similar to that of host cells and tissues. I have examined C. albicans filamentous growth in these confined chambers, in order to determine the biophysical properties of growth and substrate invasion. Using time lapse microscopy, I showed that the percentage of invasive hyphae decreased with an increase in PDMS stiffness, and determined a stiffness threshold, in which hyphae are unable to invade - likely the growth-stalling force. During invasive growth, there was a striking reduction in filament extension rate, compared to surface growth, which was dependent on PDMS stiffness. Furthermore, during this process, I observed a cell morphology change, i.e. a significant increase in cell diameter and a concomitant decrease in cell compartment length, resulting in cell volumes that were largely indistinguishable from that of surface growing cells. This morphology change was associated with a striking increase in the level of active Cdc42, the master regulator of polarity, at the hyphal tip and a concomitant depolarization of active Rho1, the glucan-synthase regulator, during invasive growth. These results indicate that changes in cell morphology during invasive growth are not due to depolarization or destabilization of active Cdc42. Rather, additional analyses suggest that mechanical forces, i.e. compression, are largely responsible for these morphological changes. The Spitzenkörper, which is a cluster of vesicles located at the filament apex adjacent to the plasma membrane, has been observed in a range of filamentous fungi. In C. albicans, electron microscopy studies have revealed that the Spitzenkörper is comprised of a uniform population of vesicles, however little was known regarding the function of this structure during filamentous growth. I have shown that the C. albicans Spitzenkörper is composed entirely of secretory vesicles. I have investigated the function of the Spitzenkörper using mutants and synthetic physical interaction approaches. Perturbation of the Spitzenkörper resulted in altered filament morphology and growth rate, strikingly an increase in filament diameter and concomitant increased growth rate was observed. Furthermore, deletion of a Spitzenkörper component dramatically reduced invasive growth. Together these results indicate that the Spitzenkörper regulates the region of new plasma membrane insertion, i.e. the ability to focus growth, and suggest that an increase in the flux of secretory vesicles compensates for less focused membrane addition. In summary, my studies reveal that mechanical forces affect C. albicans morphology and substrate invasive ability, and that the Spitzenkörper is the central link between filament morphology and growth rate, as well as substrate invasion
Caractérisation morphologique, électrophysiologique et topographique des neurones de la couche V dans un modèle murin de maladie neurodéveloppementale by Chiara Tocco( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

In mammals, the proper execution of fine voluntary movements relies on complex, but highly organized neuronal networks connecting various regions of the brain, such as the cerebral cortex, basal ganglia, pontine nuclei, cerebellum and thalamus. Understanding the genetic and molecular mechanisms underlying the neuronal organization of these circuits may improve our knowledge of how motor networks are normally established during development and affected in neurodevelopmental diseases. Among others, subcortically projecting Layer V Pyramidal Neurons (LVPNs) are central to this circuit.We have previously shown that the genetic loss of the transcription factor Nr2f1 in the developing neocortex, the evolutionary most recent region of the cerebral cortex, affects areal organization and molecular specification of LVPNs, leading to defective voluntary motor functions in both mouse models and human NR2F1 haploinsufficient patients. To further assess the contribution of Nr2f1 in the establishment of cortico-subcortical networks, we used two independent Nr2f1 conditional mutant mouse lines and investigated electrophysiological, morphological and connectivity features of LVPNs at different developmental stages.Our electrophysiological and morphological data reveal that postnatal mutant LVPNs are characterized by increased intrinsic excitability and reduced dendrite complexity, indicating that Nr2f1 plays a key role in LVPN functional maturation during cortical development. Moreover, genetic tracing of LVPN projections in mutant brains shows abnormal topographic mapping between the cortex and pontine nuclei, implying that LVPNs need to acquire their proper areal identity to establish normal subcortical projections. Overall, our data indicate that Nr2f1 is involved in the establishment of functional and structural properties of LVPNs, as well as in the topographic organization of cortico-pontine projections, first players of the cortico-ponto-cerebellar circuit involved in fine motor skills
Mécanismes moléculaires spécifiant les neurones positifs Satb2/Ctip2 dans la couche V du cortex somatosensoriel chez la souris et caractérisation de leur morphologie, connectivité, profil moléculaire et propriétés électrophysiologiques by Kawssar Harb( )

1 edition published in 2014 in English and held by 1 WorldCat member library worldwide

The mammalian cerebral cortex is subdivided into several tangential domains calledfunctional areas, deputed to the elaboration of motor and sensory inputs and implementation of motor plans. Each functional area is constituted by six layers of projection neurons with different morphologies, connectivity and molecular codes.Several transcription factors specifying different subclasses of neurons have been identified so far. Fezf2 and Ctip2 promote the specification of subcerebralPNs, whereas Satb2 promotes callosal identity, mainly by repressing Ctip2transcription through the recruitment of the NURD complex to the Ctip2 locus.However, little is known about the mechanisms specifying their features in a timeandareal-Specific manner. In this study I show that a population of cells co-Expressing molecular markers of CPN and SCPN neurons, Satb2 and Ctip2, becomes first specified in layers V and VI of rostro-Medial mouse neocortex at perinatal stages and progressively increases between P0 and P21 in somatosensory areas. I found that in neocortices lacking COUP-TFI, a transcription factor involved in arealization, the number of Satb2/Ctip2 co-Expressing cells increases abnormally in layer V of the prospective somatosensory area. I demonstrated that LMO4 ectopic and premature expression of LMO4 in COUP-TFI mutant transgenic line derepresses Ctip2 in Satb2 positive cells by disturbing the assembly of the NURD complex at Ctip2 locus. Moreover, by the use of a transgenic line expressing GFP in layer V neurons and of vital dyes, I analysed morphology, connectivity and electrophysiological activity of this hybrid class of neurons.development. Toget
Un modèle en 3D d'adipocytes de type brun dérivés de cellules pluripotentes induites humaines pour le criblage in vitro de médicaments et pour la thérapie cellulaire contre l'obésité by Xi Yao( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Obesity results from an imbalance between calorie intake and energy expenditure. Therapies based to reduce energy intake are difficult to follow in our modern life, and drugs can display adverse effects. Alternative strategies are urgently required to fight obesity and associated metabolic disorders. Brown and brown-like adipocytes (BAs) store fat, but in contrast to white adipocytes, BAs are equipped to burn glucose and lipids to dissipate energy stored. BAs also secrete adipokines that signal other organs and regulate metabolism. Therefore, BAs represent promising cell targets to promote energy expenditure and counteract obesity. However, the scarcity of BAs in human adults is a major limitation for a BA-based therapy of obesity, and the notion to increase the BA mass by transplanting BA progenitors (BAPs) in obese patients recently emerged. The proof of concept has been done in murin models. The next challenge is to identify an abundant and reliable source of human BAPs. We recently described the capacity of human induced pluripotent stem cells (hiPSCs) to generate BAPs. During my thesis, we established a procedure to generate hiPSC-BAP spheroids and a method for their differentiation at a high efficiency in hiPSC-brown-like adipospheres. The model was then enriched with Human Dermal Microvascular Endothelial Cells (HDMECs) to better mimic the adipose tissue microenvironment and to improve its therapeutic potential. BAPs derived from human iPSCs were maintained in suspension to form spheroids able to different into adipospheres. The structure of adipospheres was analysed by confocal microscopy and adipocytes were characterized at the molecular and metabolic levels. We generated adipospheres from two different hiPSC-BAP clones, which are able to fully differentiate from the surface to the core. We compared hiPSC-brown-like adipospheres with the ones generated by hanging drop method, and our model displays comparable pattern regarding to extracellular matrix and adipogenesis, despite the sizes are not defined. We also proved hiPSC-brown-like adipospheres promotes accumulation of brown-like adipocytes that are more biologically active compared to cells maintained in conventional monolayer cell cultures. In addition, hiPSC-brown-like adipospheres have a similar expression profile of extracellular matrix and G Protein-Coupled Receptors (GPCRs) compared with human adipospheres derived from subcutaneous abdominal adipose progenitors, suggested the physiological relevance of the hiPSC-adiposphere model. Moreover, hiPSC-adipospheres display a more brown-like adipogenic potential than abdominal adipospheres opening the opportunity and advantages for anti-obesity drug testing and cell based therapy to increase the BA mass in patients. Furthermore, hiPSC-adipospheres express UCP1 that can response to the stimulation of 8-CPT-cAMP or 8-Br-cGMP acutely and chronically, which indicated that our 3D model display metabolic characteristics of brown-like adipocytes. Finally, enrichment with HDMECs was performed via co culture in suspension. HDMECs functionality was tested in vitro by LDL-uptake. We proved that hiPSC-BAPs and HDMECs can co-culture in 3D and differentiate into vascularized hiPSC-brown-like adipospheres with functional tubular-like structure formed inside. Moreover, our co-cultured 3D model can secrete factors like VEGF and FGF2 to support vascularization which mimic in vivo situation.Altogether, the hiPSC-brown-like adipposphere model represents an unlimited source of human BAPs that in a near future may be a suitable tool for both therapeutic transplantation and for drug screening allowing discovery of novel and safe anti-obesity drugs
Rôle de GTPase de type Rab, Ypt6, chez le pathogène fongique opportuniste de l'homme, Candida albicans by Rohan Sanjay Wakade( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Candida albicans is a harmless constituent of the human microbiota that causes superficial infections as well as life threatening infections in immune compromised individuals. The transition from a budding form to the highly polarized hyphal form is associated with virulence and requires cytoskeleton reorganization and sustained membrane trafficking. In a range of eukaryotes, Ras related protein in the brain (Rab) G proteins and their regulators have been shown to play a central role in membrane traffic. The objective of this work is to understand the role of Rab proteins, in particular Ypt6, the homolog of Human Rab6, in the morphological transition and virulence of C. albicans. To this aim, I generated loss of function mutants and found that YPT6 is not essential for viability, yet was critical for cell wall integrity and invasive hyphal growth, with ypt6 hyphal filaments shorter compared to that of the wild type (WT). Furthermore, YPT6 was important for virulence in two murine candidiasis models. I determined that Ypt6 was localized at the late Golgi compartment during hyphal growth, where it co-localized with Arl1, a small GTPase of the Arf (ADP Ribosylation Factor) family, also required for hyphal growth and virulence. Interestingly, overexpression of YPT6 specifically rescued the hyphal growth defect of the arl1 mutant, but not the converse. Further characterization of the ypt6 deletion mutant showed that the number of Golgi cisternae is increased in this mutant compared to that of WT strain, suggesting an alteration of Golgi integrity. In addition, using live cell imaging I showed that the distribution of Actin binding protein 1 (Abp1), which is a reporter for actin patches, was altered in the ypt6 mutant, in that it was no longer restricted to the tip of the filament, as is observed in WT cells. These data suggest that the defect in hyphal growth maintenance of the ypt6 deletion mutant is at least partly associated with an alteration of the distribution of endocytic sites. Thus, I identified a critical role of Ypt6 during invasive hyphal growth and virulence in the human fungal opportunistic pathogen C. albicans and revealed an interaction between Ypt6 and Arl1 in the hyphal growth process
Impact de la mutation G380R du récepteur FGFR3 responsable de l'achondroplasie sur le métabolisme énergétique et évaluation de l'effet d'un traitement par sFGFR3 by Céline Saint-Laurent( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

L'achondroplasie est une maladie génétique rare représentant la forme la plus courante de nanisme à membres courts. Elle se caractérise par des anomalies de croissance dont les mécanismes sont très étudiés et par une forte prédisposition à l'obésité pour laquelle les causes sont inconnues. Il s'agit d'une maladie autosomique dominante causée par une mutation dans le gène du "Fibroblast growth factor receptor 3" (FGFR3). A ce jour, aucun traitement n'est disponible et, notre équipe a mis au point une thérapie par protéine recombinante montrant que l'injection d'une forme soluble du récepteur FGFR3 (sFGFR3) permet de rétablir une croissance osseuse normale chez des souris transgéniques Fgfr3ach/+. Dans une étude rétrospective, nous avons rapporté des troubles métaboliques chez des patients achondroplases avec une prise de poids de ces patients excessive entraînant une obésité essentiellement viscérale. De façon inattendue, la glycémie à jeun, l'insulinémie, le cholestérol et les triglycérides restent dans les valeurs basses de la norme. Nous avons observé les mêmes résultats dans notre modèle murin. Nous avons alors montré qu'une modification des cellules souches mésenchymateuses pourrait modifier leur potentiel de différenciation. Il est intéressant de noter que, chez les souris traitées avec sFGFR3 pendant la période de croissance, ces dérégulations métaboliques sont corrigées et le potentiel de différenciation des cellules souches est rétabli. Le sFGFR3 s'avère être un traitement prometteur pour l'achondroplasie, non seulement pour rétablir la croissance osseuse mais aussi pour prévenir les dérégulations métaboliques et le développement de l'obésité viscérale
Etude d'assemblage et des fonctions des isoformes oncofoetales de la fibronectine by Georgios Efthymiou( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Évolution de la plasticité développementale chez le nématode Caenorhabditis elegans by Bénédicte Billard de Saint Laumer( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Adaptive developmental plasticity is a common phenomenon allowing organisms to cope with heterogeneous habitats through sensation of environmental cues inducing alternative phenotypes. While there is increasing information on the molecular mechanisms regulating developmental plasticity as well as ample evidence that such plasticity displays natural genetic variation, we still have limited information on how the degree of sensitivity to environmental cues regulating plasticity evolves through specific changes at the molecular level. Focusing on the plastic life history switch between reproductive and arrested (dauer) developmental stages in the nematode Caenorhabditis elegans, we characterized the molecular nature of enhanced sensitivity to dauer-inducing cues in the wild isolate JU751. This isolate has the unique tendency to readily form dauers not only at moderate population density but also in response to an array of diverse, yet relatively mild environmental stressors (high temperature, starvation, oxidative stress, pathogens). Based on QTL mapping, we identified a 92bp deletion in the presumptive promoter region of the gene eak-3 - drastically reducing eak-3 expression in JU751 - as the underlying causal variant.Eak-3 is exclusively expressed in the endocrine XXX cells, indicative of its role in affecting signalling through the steroid hormone dafachronic acid, the central downstream component controlling the binary dauer decision. Constitutively reduced levels of eak-3 thus reduce steroid hormone levels, hence lowering the environmental sensitivity threshold for dauer induction, consistent with the observed enhancement of JU751 dauer induction in response to any of several different environmental cues. Therefore, evolution of increased environmental sensitivity of the JU751 dauer decision has occurred through modulation of a hormonal level. Testing for potential pleiotropic consequences of the eak-3 variant in JU751 using allelic replacement lines, we find this deletion to cause a subtle, yet significant delay of postembryonic reproductive growth in favourable conditions, delaying age at reproduction by ~3 hours. This developmental delay is indeed due to reduced steroid hormone signalling, suggesting that acquisition of the eak-3 deletion in JU751 has led to the emergence of a trade-off between developmental timing and environmental sensitivity of a plasticity switch. Consistent with this scenario, we experimentally show the eak-3 deletion allele to be rapidly outcompeted in environments favouring reproductive (non-dauer) growth; in contrast, the deletion may provide a significant fitness advantage through facilitated dauer production in highly stressful environments. Together, our results show how a specific molecular change can underlie the evolution of adaptive developmental plasticity, and they further provide a rare example illustrating how seemingly complex life history trade-offs can emerge through hormonal pleiotropy caused by a single genetic change
Rôle d'Otx2 dans les photorécepteurs de la rétine mature by Pasquale Pensieri( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Si le rôle du facteur de transcription Otx2 dans le développement de la rétine est bien compris, sa fonction dans la rétine adulte reste floue. L'expression d'Otx2 est maintenue dans l'épithélium pigmenté rétinien (RPE), les photorécepteurs (PR) et les cellules bipolaires durant toute la vie. Des travaux antérieurs ont montré que l'ablation du gène Otx2 dans la rétine adulte conduit à une dégénérescence des PR, suggérant qu'il a un rôle dans leur maintenance. Il a ensuite été montré que l'expression d'Otx2 restreinte dans le RPE est à la fois nécessaire et suffisante pour la survie des photorécepteurs, ce qui indique une fonction neuroprotectrice non autonome dans ces cellules. Ces résultats n'expliquent pas la fonction de la protéine Otx2 endogène dans les PR. Afin de l'élucider, nous avons utilisé la lignée de souris Crx-CreERT2 inductible pour procéder à la délétion du gène Otx2 spécifiquement dans les PR. L'histologie a confirmé que l'expression d'Otx2 endogène n'est pas nécessaire à la survie des PR ni au maintien de leur identité cellulaire chez l'adulte. Cependant, nous avons constaté qu'Otx2 est impliqué dans l'adaptation visuelle en régulant le mouvement de l'arrestine induit par la lumière, dans les photorécepteurs. L'arrestine est transportée entre les segments externes du PR, où il s'accumule à la lumière, et les segments internes et le soma, où il s'accumule dans l'obscurité, pour moduler la sensibilité du PR, en réponse à différentes intensités lumineuses. Ce trafic est compromis après délétion d'Otx2 dans les PR : l'arrestine reste bloquée dans les segments internes et dans le soma, même après une exposition prolongée à la lumière. Des tests comportementaux ont montré que les souris mutantes sont fortement photophobes. Les mécanismes détaillés restent à élucider.Pour déchiffrer le réseau de gènes contrôlé par Otx2 dans les PR, nous avons effectué des analyses temporelles par RNA-seq au décours de l'inactivation d'Otx2 dans les PR. Aucun gène de la cascade de phototransduction ne semble dérégulé. Par contre, l'expression de certains gènes de la matrice extracellulaire et, de manière surprenante, d'un groupe de gènes spécifiquement impliqués dans la mélanogénèse dans le RPE, et déjà connus pour être des cibles directes d'Otx2, est diminuée. Un examen attentif des souris porteuses d'une délétion d'Otx2 spécifique dans les PR a confirmé que le niveau de protéine Otx2 dans les noyaux du RPE est réduit, tandis que la protéine Otx2 peut maintenant être détectée dans les segments externes de PR. Au vu de ces données et de l'effet neuro-protecteur d'Otx2 joué par le RPE, nous avons émis l'hypothèse d'un transfert direct de la protéine Otx2 du RPE aux PR. Pour prouver cette hypothèse, des vecteurs viraux dirigeant l'expression d'une forme d'Otx2 étiquetée, spécifiquement dans les cellules du RPE, ont été générés et utilisés pour l'injection sous-rétinienne chez la souris. Après transduction du RPE, nous avons recherché si la forme d'Otx2 étiquetée pouvait être détectée dans les PR. Nous avons constaté que dans la rétine contrôle, un transfert constitutif d'Otx2 est actif à faible débit. Après l'induction du KO dans les PR, le taux de ce transfert est augmenté, agissant probablement comme une réponse neuro-protectrice. Une telle augmentation du transfert explique bien la réduction du taux de protéine Otx2 dans le RPE et la diminution d'expression des gènes de la mélanogenèse. La protéine Otx2 transférée semble être transportée des segments externe et interne des PR vers les synapses situées dans la couche plexiforme externe, ce qui suggère que sa fonction neuro-protectrice met en jeu des mécanismes différents de sa fonction génomique classique de facteur de transcription.En conclusion, cette étude a révélé une nouvelle fonction de la protéine Otx2 endogène dans l'adaptation des PR à la lumière et a démontré l'existence d'un transfert de protéine Otx2 exogène, du RPE vers les PR, avec un rôle neuro-protecteur présumé
Identification d'un nouveau rôle de la E3-ubiquitin ligase Mindbomb1 dans la voie Polarité Cellulaire Planaire by Vishnu Saraswathy( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

La morphogenèse est le processus qui définit la forme d'un organisme (ou d'une partie d'un organisme) nécessaire à son bon fonctionnement. Au cours de l'embryogenèse, la morphogenèse d'un organe nécessite des processus incluant la division cellulaire, les mouvements cellulaires et la différenciation cellulaire. Cependant, on sait peu de choses sur la façon dont ces différents processus sont coordonnés au cours de la morphogenèse d'un organe. Au cours de ma thèse, j'ai étudié deux voies de signalisation cellulaire différentes qui régulent la morphogenèse au cours de l'embryogenèse du poisson zèbre. Mon étude a révélé que la voie de signalisation Notch et la voie PCP (Polarité Cellulaire Planaire) contrôlée par Mib1 régulent respectivement la morphogenèse du tube neural et l'extension de l'axe embryonnaire.Au cours de la première partie de ma thèse, j'ai étudié le rôle de la signalisation de Notch dans la morphogenèse du tube neural du poisson zèbre. La signalisation Notch a déjà été bien étudiée pour son rôle dans la régulation de la neurogenèse lors du développement du poisson zèbre. Cependant, on ne sait pas si et comment la signalisation Notch régule la morphogenèse du tube neural du poisson zèbre. L'épithélialisation et la c-division sont des événements importants au cours de la morphogenèse du tube neural du poisson zèbre. Nos résultats montrent que, en plus de synchroniser la spécification des cellules neuronales, la suppression de la neurogenèse induite par Notch est essentielle pour l'acquisition de l'architecture neuroépithéliale et pour la réalisation de c-division. Ainsi, la signalisation Notch permet de former la moelle épinière de poisson zèbre.Les observations de la première partie de ma thèse ont conduit à l'identification du rôle de Mindbomb1 (Mib1) dans la signalisation PCP. Mib1, une ligase ubiquitine-E3 nécessaire à l'activation de Notch, régule les mouvements d'extension convergence (CE) nécessaires à l'élongation de l'axe de l'embryon au cours de la gastrulation du poisson zèbre. De manière intéressante, nous avons montré que Mib1, indépendamment de sa fonction dans la signalisation Notch, agit dans la voie PCP pour réguler l'extension de l'axe de l'embryon. Dans la voie de la PCP, Mib1 agit comme une ligase ubiquitine-E3 et régule l'endocytose du composant de la PCP Ryk afin d'assurer la médiation de la CE lors de la gastrulation. Ainsi, notre étude a révélé que, indépendamment de son rôle dans la signalisation Delta / Notch, Mib1 est important pour la voie PCP lors de la gastrulation du poisson zèbre
Analyse génétique du trafic intracellulaire du morphogène Hedgehog chez la Drosophile by Tanvi Gore( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Hedgehog (Hh) is a conserved secreted morphogen involved in an array of developmental processes. Using Drosophila as a model, during my thesis we aimed to ask how the secretion, extraction and transport of Hh protein are regulated at the site of its production. To understand the positive regulators of Hh secretion and transport we designed and performed a genome-wide RNAi screen in Drosophila to identify new regulators of Hh transport and identified the small GTPase Rab8 as a novel component required for Hh trafficking. According to our proposed model, there are two pools of secreted Hh. The apical pool is needed for long range target gene activation, and basolateral pool for short range target gene activation. It is not clear how Hh is sorted apico-basally in the producing cells. Interfering with Rab8 function in the Hh producing cells extends Hh short range targets. Conversely, it reduces the long range Hh targets, suggesting that interfering with Rab8 function in the Hh producing cells impairs Hh trafficking, thus hampering the fine tuning between the two secreted pools of Hh. Moreover, using live assays to track the dynamics of endogenous Hh internalization, we observed that loss of Rab8 in Hh producing cells does not affect its primary secretion, but causes defects in Hh endocytosis, subsequently affecting its gradient activity. We hypothesize a model where Hh is targeted for primary secretion to the apical side of the wing disc, which then is internalized, and this internalized Hh is then directed for recycling which is essential for its long range activity
Gallium, un candidat prometteur pour le traitement des pathologies osseuses by Ivana Strazic( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

In bone reconstructive surgery biomaterials commonly replace the missing tissue and in case of pathologies can also serve as vectors for drug delivery. The semi-metallic element gallium (Ga) is used for the treatment of several disorders associated with accelerated bone resorption, due to its inhibitory action on bone-resorbing cells (osteoclasts). Since Ga can be incorporated into the structure of bone biomaterials, we embarked on characterising the biological properties of novel Ga-loaded materials. In vitro, we observed a decrease in osteoclast differentiation and the upregulated expression of several osteoblastic markers (bone-forming cells) in the presence of Ga-loaded biomaterial. In vivo, using a rat bone defect model, we showed an increase in newly formed bone tissue in implants filled with Ga-loaded biomaterial vs. control. Taken together, our data indicate that Ga-loaded biomaterials provide biocompatible substrates allowing bone cells survival and improved bone reconstruction in vivo. Taking into account antitumoral effects of Ga, largely described in literature, we also investigated its impact on a bone metastatic model. Using an aggressive human cancer cell line selected for its ability to invade bone tissue, we showed that Ga could reduce cancer cell proliferation and viability and reverse excessive osteoclastogenesis in bone metastatic environment. Moreover, we demonstrated that Ga modulated the expression of several marker genes hindering the tumour-propagating potential of cancer cells. Thus, due to its inhibitory action on cancer cells, Ga could represent an attractive additive to biomaterials used for tissue reconstruction after tumour resection
Sox8 compense la perte de Sox9 pendant le développement testiculaire physiopathologique chez la souris présentant une perte de fonction du gène R-spondin1 by Nainoa Richardson( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

In humans and mice, testicular development in XY gonads involves SRY/SOX9 signaling to promote Sertoli cell differentiation and their formation as testis chords. For ovarian development in XX gonads, RSPO1/WNT/beta-catenin signaling is the main pathway for granulosa cell differentiation and their subsequent assembly into follicles. Indeed, XY Sox9 mutant mice develop ovaries, and XX Rspo1 mutant mice develop ovo-testes, a gonad containing a testicular and an ovarian part. In XX Rspo1 mutant mice, ovo-testicular development involves precocious differentiation of some granulosa cells and their and reprogramming as Sertoli cells. Thus, these single mutant studies demonstrated that SOX9 and RSPO1 are required for testicular and ovarian development respectively, and that SRY is dispensable for testicular development in XX Rspo1 mice. Interestingly, gonad development in XY and XX Rspo1 Sox9 double knockout (DKO) mice has challenged the requirement of SOX9 for testicular development. In XX Rspo1 single mutants, it was assumed that Sertoli cell differentiation was SOX9-dependent, but co-inactivation of Sox9 in DKO mice does not impair the ovo-testicular phenotype. For XY Sox9 single mutant mice developing ovaries, co-inactivation of Rspo1 in XY DKO mice rescues the sex reversal, though the testes are hypo-plastic. Thus, in XY and XX Rspo1 Sox9 DKO mice, SOX9 and/or SRY are dispensable for testicular differentiation, indicating that an alternate testis factor exists. For my research project, we hypothesized that a SOX9-related transcription factor, SOX8, acts redundantly for testicular development in XY and XX Rspo1 Sox9 DKO mice. Thus, to first establish redundancy among the SOX factors, we first analyzed their expression in Rspo1 mutant mice lacking Sox8 or Sox9, and then generated and analyzed gonad development in XY and XX Rspo1 Sox8 DKO mice. Then to test our hypothesis, we studied Rspo1 Sox8 Sox9 triple knockout (TKO) mice. We predicted that a loss of both Sox genes in TKO mice would prevent granulosa cell reprogramming as Sertoli cells and subsequent testicular development. To characterize gonad development and their effects in DKO and TKO mice, we performed analyses in embryonic day 17.5 (E17.5) mice, when granulosa-to-Sertoli cell reprogramming begins in XX Rspo1 single mutants; in juvenile post-natal day 10 (P10) mice, when gonad fate is set; and in young adult P40 mice. We examined a variety of parameters including gonad morphology and secondary sex characteristics, as well as gonad organization and cell population by histological and immunostaining analyses. We report that SOX8 and SOX9 are expressed independently in XY and XX Rspo1 Sox9 DKO and Rspo1 Sox8 DKO gonads in embryonic and juvenile mice. Next, XY and XX Rspo1 Sox8 DKO mice developed testes and ovo-testes, indicating that loss of one SOX factor does not impair testicular differentiation, as in XY and XX Rspo1 Sox9 DKO mice. In XY and XX Rspo1 Sox8 Sox9 TKO mice, granulosa-to-Sertoli cell reprogramming was impaired at E17.5 and post-natal gonads lacked testicular development. Thus, SOX8 can compensate for the loss of SOX9 in Rspo1 Sox9 DKO mice. In addition, gonads in XY and XX TKO mice developed as atrophied ovaries, indicating that ovarian fate is partially maintained.In total, we investigated the etiology of pathophysiological testicular development in RSPO1 loss-of-function mice. Remarkably, though SOX8 is dispensable for male sex determination in mice, it can promote testicular differentiation in the absence of SRY and SOX9 because of functional redundancy with SOX9. Thus, in human cases of sex reversal where testicular development cannot be explained by misexpression of SRY or SOX9, SOX8 could be a causative factor
Rôle du facteur de transcription Otx2 dans le développement normal et tumoral du cervelet by Salsabiel El Nagar( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

Medulloblastomas (MB) are the most common brain tumors in paediatrics. They appear during development in the posterior part of the brain, mainly in cerebellum. MB can be stratified in four groups: the WNT and SHH groups, where these signalling pathways are aberrantly activated, and the groups 3 and 4, which display chromosomal abnormalities and multiple amplifications, including c-Myc (group 3) and N-Myc (group 4). One of the most frequent genetic alterations in MB is the overexpression of the Otx2 transcription factor (in 75% of cases). This factor, which is essential for central nervous system development, is expressed in granule cell precursors (GCP) of the cerebellum, which represent the cell of origin of the majority of MB. During the perinatal period, GCPs undergo intense proliferation in response to Sonic Hedgegog (SHH), making them particularly susceptible to tumorigenesis. During this thesis, we were interested in examining the function of Otx2 in GCPs. We have shown that conditional ablation of Otx2 leads to a GCP proliferation defect and that Otx2 stimulates the proliferation of these cells independently of the Shh signaling pathway. Moreover, ablation of Otx2 in a mice model of Shh-dependent medulloblastomas yielded very interesting results: while Otx2 does not seem to be required for the initiation of these tumors, it is essential for their long-term maintenance. In parallel, we tried to create a new murine model for the MB group 3 by inducing the expression, during the postnatal period, of an active dominant of c-Myc in cells expressing Otx2. This approach yielded unexpected results: choroid plexus carcinomas, instead of MB, were obtained
Rôle du facteur de transcription Otx2 dans le contrôle de la prolifération des précurseurs granulaires du cervelet et des médulloblastomes by Almahdi Chakroun( )

1 edition published in 2016 in French and held by 1 WorldCat member library worldwide

The homeobox transcription factor Otx2 is essential for the development of the central nervous system. During cerebellum development, Otx2 is expressed by granule cell precursors (GCPs), which have a high proliferation rate. Deregulation of GCPs proliferation may favor oncogenic processes, as seems to occur in medulloblastoma (MB), a malignant and invasive tumor of the cerebellum. A recurrent genetic alteration in medulloblastoma is the overexpression of Otx2 in 75% of the cases. The objective of this thesis is to study the role of Otx2 in the control of proliferation during normal and oncogenic development of the cerebellum. First, we investigated the role of Otx2 in the control of GCPs proliferation. Our results show that Otx2+ GCPs have an increased proliferation rate compared to «Otx2-» GCPs. In the second part of this work, we tested the oncogenic potential of Otx2 using the medulloblastoma cell line HD-MB03. We performed gain and loss of function experiments to analyze the effect of Otx2 expression on the proliferation of this cell line. Our results indicate that the overexpression of Otx2 increases the proliferation rate of HD-MB03 tumor cells. Conversely, Otx2 silencing significantly decreases it. Finally, to shed the light on the mechanism of action of Otx2 in the control of proliferation in cerebellum and medulloblastoma, we analyzed Otx2 protein partners in both cases by mass spectrometry analysis after immunoprecipating Otx2-protein complexes. We identified several protein partners that play an important role in cell cycle regulation, more specifically in S and G2M phases. Our project shows a pro-proliferative effect of Otx2 in cerebellum and medulloblastoma
Étude du rôle des gènes SoxC au cours du développement du rein de souris by Vladimir Kozlov( )

1 edition published in 2020 in English and held by 1 WorldCat member library worldwide

Rôles du Perlécane de la membrane basale dans la morphogénèse épithéliale chez Drosophila melanogaster by Raphaël Bonche( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

The Basement Membrane (BM) is a specialised extracellular matrix which surrounds organs and provides them with a mechanical support. During development, the BM has to adapt to the morphogenesis of the tissues to which it is associated, i.e. to the changes of their volume and shape. This implies a modulation of the BM's biogenesis in terms of the amount that is deposited and of its composition. Morphogenesis being controlled by the morphogens, these latter could directly govern this biogenesis. Nevertheless, the link between these molecules and the regulation of BM's components synthesis remains poorly characterized. In addition, the BM is also a signalling platform for the cells which it coats. Thus, some of its components could interact with morphogens and control their activity, ensuring a coupling between these two processes. Perlecan (Pcan), the major heparan sulfate (HS) chains proteoglycan of the BM, has several putative isoforms in all species. It binds in vitro to the other components of the BM and to the morphogens through its HS chains or its core protein. Yet, the roles of Pcan and its isoforms in vivo (i) for the biogenesis and the mechanical properties of the BM and (ii) for the morphogens' signalling are not fully understood. I therefore developed two projects. Using the epithelia of the wing imaginal disc in Drosophila, we showed that Pcan participate to BM biogenesis. Indeed, without Pcan, the incorporation of Collagen IV (Col IV), another core BM component, is altered. Moreover, the squamous epithelial cells of the wing disc change their shape, becoming cuboidal, and wing formation is compromised. I proved that a reduction in the Col IV amount allows to largely restore this phenotype. In addition, I demonstrated that the compression of the squamous epithelium increases in absence of Pcan. Thus, Pcan provides elasticity to the BM, counteracting the Col IV which gives it rigidity. My data also indicate that the microtubule cytoskeleton could relay intracellularly the mechanical variations due to the BM modification. Our results suggest for the first time that interaction between Pcan and Col IV controls the network organisation of the latter, allowing to modulate its action. For the second project, I first demonstrated the existence of two types of isoforms in Drosophila: one with a domain I, required for the HS chains addition, and a second without domain I, theoretically devoid of HS chains. My results suggest that the Pcan deposited in the BM of the wing disc comes from three different sources, synthesizing different isoforms. I showed that the wing disc mainly produces a form without domain I which is likely to be directly incorporated in its BM. Next, I found that the expression of this isoform in the disc is positively controlled by the Dpp-BMP2/4 signalling pathway, while the expression of the isoform with domain I is repressed by the same pathway. Finally, I uncovered that Pcan acts generaly as an inhibitor of the Dpp pathway by potentially affecting the level of the ligand in the extracellular space, but that the two isoforms act in an opposite manner on the Dpp pathway in the wing disc. In conclusion, my data show the existence of a feedback loop between morphogens, which orchestrate morphogenesis, and the BM, one of the keystone of the tissulare architecture
Rôle des signaux pro-survie du récepteur Fas/CD95 dans le cancer colorectal : importance du dialogue moléculaire entre Fas et l'EGFR (Epidermal Growth Factor Receptor) by Ngoc Ly Ta( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Colorectal cancer (CRC) is the third most common malignant disease and the second most frequent cause of cancer-related death. The ErbB family of transmembrane receptor tyrosine kinases has been identified as a major driver of the development and progression of CRC and one its best-known member, the epidermal growth factor receptor (EGFR /ERBB1/Her1), considered one of the most important targets in CRC treatment. Two others members of the ErbB family, the receptors Her2 and Her3, also emerge as important new targets for CRC due to the somatic mutation, gene amplification or resistance to the anti-EGFR therapies. The transmembrane protein, Fas (TNFRSF6/CD95), is a member of the tumor necrosis factor receptor superfamily (TNFRSF). It can transmit multiple signals that lead to completely different cell fates. Depending on cellular contexts, Fas either initiates cell death by apoptosis, which is essential for shutting down chronic immune responses and preventing autoimmunity and cancer, or stimulates cell survival, proliferation, and motility, which can promote autoimmunity, cancer growth, and metastasis. With increasing evidence of Fas-mediated pro-survival signaling, the cancer-promoting activities of Fas are now recognized as significant and clinically relevant. While this signaling versatility has been particularly well demonstrated in colon cancer, the molecular mechanisms underlying the survivals pathways are still largely unknown. In this context, the main aim of my Ph.D. project was to study the importance of the crosstalks between Fas and the ErbB family members and more specifically to determine whether the Fas signaling could influence the cancer-promoting signaling of EGFR.More precisely, I describe how the Fas tyrosine phosphorylation status strongly influences the signaling of the EGFR pathway in colorectal cells. My data demonstrate that Fas in its prosurvival state, phosphorylated at Y291 (pY291-Fas), indeed interacts with EGFR and that this interaction significantly intensifies EGFR signaling in anti-EGFR-resistant colorectal cancer cells via the Yes-1/STAT3-mediated pathway. The pY291-Fas accumulates in the nucleus upon EGF treatment and promotes the nuclear localization of phospho-EGFR and phospho-STAT3, the expression of cyclin D1, the activation of STAT3-mediated Akt and MAPK pathways, and finally the cell proliferation and migration. Additionally, I also uncover the potential role that Her3, may play along with Fas, in the colorectal cancer cell escape from anti-EGFR inhibition. All together my Ph.D. studies provide a better understanding of the role of the Fas survival pathways in the ErBb signaling in CRC. Importantly, by demonstrating a connection between the emergence of resistance to anti-ErbB therapies and the Fas pro-survival signal, my work provides a rationale for the development of Fas/phospho-Fas targeted therapy as a new therapeutic option for overcoming anti-EGFR, in patients with secondary anti-EGFR resistance
Étude du mécanisme d'activation de la voie de signalisation canonique de Hedgehog chez la drosophile by Cécile Giordano( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

Hedgehog (Hh) is a secreted morphogen that controls growth and differentiation in both vertebrates and invertebrates. The dysregulation of its activity leads to severe developmental defects, and the onset of cancer in adults. In Drosophila, the Hh signal transduction is initiated by the binding of Hh to its receptor Patched (Ptc). This induces the stabilization of the transmembrane protein Smoothened (Smo) and the subsenquent activation of a transduction complex consisting of 5 proteins: the kinases Fused (Fu), PKA and Gprk2, the kinesin Costal2 (Cos2), and the transcription factor of the pathway Cubitus Interruptus (Ci). The aim of my thesis was to study the regulation and molecular interactions between the different components of the transduction complex. Thanks to complementary techniques, I have shown that in absence of Hh the proteins Fu and PKA interact in C-terminal part of Ci, whereas on the presence of Hh induces their relocalization toward the N-terminal domain of Ci. I have proved that the trigger element of this moving is Smo. In presence of Hh, Smo goes into transduction complex, allowing the activation and the moving of Fu toward N-terminal domain of Ci. This relocalization is responsible of Ci phosphorylation and activation. My thesis reveals the importance of conformational changes inside the transduction complex of Hh pathway. As the mechanism of transduction is conserved between species, my PhD provides research elements in order to better understand the normal and abnormal functioning of cells
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Centre national de la recherche scientifique (France). Unité mixte de recherche (7277)


Institut national de la sante et de la recherche medicale (France). U1091

Institute of Biology Valrose facility in Nice, France

English (14)

French (6)