Les précédents projets de l’équipe se concentraient sur l’étude de la relation entre l’activation des récepteurs aux cannabinoïdes et leurs différentes cibles cellulaires, en utilisant des approches d’imagerie quantitative sur des neurones en culture in vitro. Au cours de ces dernières années, nos axes de recherche ont convergé vers l’étude de la régulation de la structure neuronale par les cannabinoïdes. Les techniques utilisées au laboratoire vont de l’imagerie quantitative de l’activation des RCPG dans des cultures neuronales d’hippocampes à l’utilisation de modèles animaux de plasticité cérébrale.

Les projets actuels de l’équipe nécessitent l’utilisation et le développement de nouveaux outils technologiques afin d’appréhender, à différentes échelles spatio-temporelles, le rôle du cytosquelette acto-myosine hautement dynamique dans la fonction neuronale et dans la pathogenèse neuropsychiatrique. L’un de ces outils, l’imagerie fonctionnelle par ultrasons (fUS), s’est révélé être particulièrement adapté pour étudier la plasticité fonctionnelle du système nerveux central grâce à l’évaluation du couplage neurovasculaire. Ainsi, une part importante de nos efforts est dirigée vers le développement technologique de cette technique de pointe, à la fois en collaboration et en interne, dans le but d’imager les conséquences fonctionnelles du remodelage dépendant de la contraction acto-myosine sur la structure cérébrale et la connectivité.

 

 

2.5.0.0

Le cœur est le tout premier organe fonctionnel chez les vertébrés pendant le développement embryonnaire.  Des défauts du développement cardiaque entraînent un grand nombre de malformations appelées cardiopathies congénitales (CHDs – Congenital Heart Diseases), qui représentent l’anomalie congénitale la plus fréquente, touchant près de 1% des nouveaux-nés.  L’étude des mécanismes cellulaires qui conduisent à la formation du coeur est nécessaire pour comprendre l’origine des CHDs.

La morphogénèse du sytème cardiovasculaire dépend de processus cellulaires et génétiques très complexes. Le département DevCard comprend trois équipes (Michel Pucéat, Francesca Rochais et Stéphane Zaffran) qui s’intéressent aux mécanismes moléculaires et cellulaires impliqués dans la fonction et dans le développement cardiaque normal et pathologique. A l’aide de modèles animaux et cellulaires, le département cherche à identifier les réseaux de régulation importants pour le développement du cœur, des vaisseaux sanguins, des valves cardiaques, mais aussi au cours de régénération et la réparation cardiaques.

Des profils lipidiques anormaux sont souvent associés à un métabolisme altéré dans les cellules tumorales, caractéristique du cancer. Notre objectif est d’élucider la façon dont le métabolisme des sphingolipides (SLs) affecte les processus biologiques clés qui sous-­‐tendent le développement du cancer, comme la mort, la prolifération et la migration cellulaires, le remodelage du stroma tumoral et la réponse immunitaire. Nous étudions en particulier la contribution des SLs dans le développement du mélanome cutané et du cancer du sein. Non seulement ces formes de cancer sont fréquentes et/ou résistantes aux thérapies actuelles, mais elles présentent également des dérégulations du métabolisme des SLs. Notre objectif ultime est de cibler le métabolisme des SLs afin d’améliorer les thérapies antitumorales, donc prévenir la progression de la tumeur et surmonter la résistance aux médicaments anticancéreux, aux cytokines et aux cellules immunitaires.

Our team investigates how Toxoplasma gondii is able to co-opt specific host cell signaling pathways upon invasion. Along the way, we uncovered novel effector proteins that are singularly exported beyond the vacuole-containing parasites and reach the host cell nucleus to rewire the host genome expression. A second avenue of investigation of our team is to study the epigenetic mechanisms involved in the regulation of the developmental transition between acute and chronic stages of infection. Along the way, we discovered a family of benzoxaborole compounds that efficiently prevent parasite growth.

The team’s previous projects were mainly focused to decipher the closely intertwined relationship between cannabinoid receptor activation and sub-neuronal targeting, by using quantitative in vitro imaging approaches of neurons. In the last years, we became increasingly interested in the understanding of cannabinoid-mediated regulation of neuronal structure. Established techniques range from molecular constructions through imaging-based measurements of GPCR activation in cultured hippocampal neurons to the use of animal models of cerebral plasticity.

Current projects of the team are targeted to develop and use new tools to better understand, at multiple spatio-temporal scales, the role of the highly dynamic actomyosin cytoskeleton in neuronal function and neuropsychiatric pathogenesis.

Cannabinoids contract neurons

We have recently identified the contraction of the neuronal actomyosin cytoskeleton as a mechanism conveying a wide-ranging inhibitory role for cannabinoids in neuronal expansion and growth (Roland et al., eLife, 2014). This mechanism acts downstream of cannabinoid receptor CB1R, the major brain target of endocannabinoids and marijuana, atypically coupled to G12/G13 proteins and the Rho-associated kinase ROCK. Such modulation of the neural actomyosin cytoskeleton has not yet been reported downstream of neurotransmitter GPCRs. Therefore our results open previously unexpected perspectives in the study and comprehension of brain function.

Functional consequences of actomyosin remodelling in the brain

Ultrafast functional Ultrasound (fUS) imaging revealed is adapted to access nervous system function through imaging the neurovascular coupling (Osmanski et al., Nat Commun, 2014; Errico et al., Nature, 2015). An important part of our current efforts is focused to further develop this powerful tool either in collaborative projects or in-house, the latter focused on imaging the functional consequences of actomyosin remodeling on brain structure and connectivity.

5 MAIN PUBLICATIONS

  1. Várkuti BH, Képiró M, Horváth IÁ, Végner L, Ráti S, Zsigmond Á, Hegyi G, Lenkei Z, Varga M, Málnási-Csizmadia A. A highly soluble, non-phototoxic, non-fluorescent blebbistatin derivative. Sci Rep. 2016 May 31;6:26141. doi: 10.1038/srep26141.
  2. Errico C, Pierre J, Pezet S, Desailly Y, Lenkei Z, Couture O, Tanter M. Ultrafast ultrasound localization microscopy for deep super-resolution vascular imaging. Nature. 2015 Nov 26;527(7579):499-502. doi: 10.1038/nature16066.
  3. Osmanski BF, Pezet S, Ricobaraza A, Lenkei Z, Tanter M. Functional ultrasound imaging of intrinsic connectivity in the living rat brain with high spatiotemporal resolution. Nat Commun. 2014 Oct 3;5:5023. doi: 10.1038/ncomms6023.
  4. Roland AB, Ricobaraza A, Carrel D, Jordan BM, Rico F, Simon A, Humbert-Claude M, Ferrier J, McFadden MH, Scheuring S, Lenkei Z. Cannabinoid-induced actomyosin contractility shapes neuronal morphology and growth. Elife. 2014 Sep 15;3:e03159. doi: 10.7554/eLife.03159.
  5. Thibault K, Carrel D, Bonnard D, Gallatz K, Simon A, Biard M, Pezet S, Palkovits M, Lenkei Z. Activation-dependent subcellular distribution patterns of CB1 cannabinoid receptors in the rat forebrain. Cereb Cortex. 2013 Nov;23(11):2581-91. doi: 10.1093/cercor/bhs240.

Metastasis can be considered as the end product of a multistep bio-mechano-chemical process where cancer cells disseminate to distant organs and home in a new tissue microenvironment (Fig.1). Metastases are resistantto multiple therapies and are responsible for the large majority of cancer-related deaths. It is now clear that the invasion-angiogenesis-metastasis cascade is not only dependent on genetic and epigenetic alterations within cancer cells, but also involves non-neoplastic stromal cells that contribute to cancer progression. However, the molecular and cellular mechanisms driving metastasis formation remain to be elucidated and better described in a realistic in vivo context. In this context, tumor cells interact with their surrounding microenvironment and corrupt it to their own benefit. For example, exosomes are small extracellular vesicles, which recently emerged as potent mediators involved in this communication. These vesicles are from an endosomal origin, contain proteins, mRNAs, non-coding RNAs and DNA; they circulate in all our body fluids and can be internalized by specific distant cells and ultimately deliver a functional message. Tumor cells release large amounts of exosomes bearing tumoral markers, which can subsequently disseminate at distance. In addition, tumor exosomes contain pro-metastatic factors that shape pre-metastatic niches (PMN), before the actual arrival of tumor cells, while determining tumor metastatic organo-tropism. These properties have promoted exosomes as new targets for anti-tumoral therapies and major candidates for non-invasive diagnosis in cancer using liquid biopsies (blood and urine), and intense research is currently conducted to identify exosome-carried biomarkers.

Development of the cerebral cortex and adult hippocampal neurogenesis are complex processes where huntingtin, the protein mutated in Huntington disease, plays a central role. Understanding these mechanisms will open new avenues potentially leading to treatment of Huntington disease and other neuropathologies.

Our overall goal is to understand the mechanisms coordinating division, cell fate choices and differentiation of neuronal stem/progenitor cells during development and adulthood. We are tackling these issues through the study of one protein, huntingtin. Huntingtin is the perfect model protein, being a scaffold for complexes involved in spindle orientation, cell-cell junctions and cell polarization. Furthermore, huntingtin is mutated in Huntington disease, an inherited neurodegenerative disorder with adult onset. Studying huntingtin thus allows integration of cellular mechanisms and physiological and pathophysiological conditions.

More specifically, we are studying the contribution of huntingtin to different steps of cortical development and adult hippocampal neurogenesis. We aim to define the molecular complexes involved. We also address the questions of how these mechanisms participate in the proper establishment and maintenance of neuronal networks and whether these pathways are altered in Huntington disease. Our working hypothesis is that abnormal development could be a predisposing factor contributing to the symptoms observed in Huntington disease. In the adult, we propose that the depressive behaviour observed in patients is not just an epiphenomenon to a severe disorder with a fatal outcome, but the result of a modification in the biological function of huntingtin in adult neurogenesis.

GIN – Inserm U1216 – University Grenoble Alpes

Lab members: Fabienne Agasse; Monia Barnat; Barbara Braz; Caroline Benstaali; Mariacristina Capizzi; Rémi Carpentier; Julien Le Friec; Elodie Martin; Doris Wennagel.