Department of Fundamental Neurosciences

Fields | Projects and contracts | Collaborations | Equipments

Research directions

Metabolic signaling and neuron-glia interactions

The brain accounts for approximately 20% of the total body glucose consumption. Furthermore, there is a tight link between the level of local electrical activity of neuronal circuits and the local consumption of energy equivalents. An important cellular partner, the astrocyte, has been shown to play a highly dynamic role in the regulation of this so-called neurometabolic coupling. The main focus of our research is precisely that of the interactions between astrocytes and neurons at the level of energy metabolism. To gain access to the dynamic aspects of these interactions, we use optical microscopy tools, in particular fluorescence microscopy, UV flash photolysis, combined with electrophysiology. As examples (see recent publications below), we recently measured in real time changes in cytosolic Na+ concentration and of ATP hydrolysis in astrocytes caused by the cellular uptake of the excitatory neurotransmitter glutamate. Our latest results show that astrocytes respond to several stimuli by sending long-distance intercellular signals, not only by the well-known Ca2+ waves but also by Na+ waves. This new form of communication within the astrocyte network is accompanied by a wave of increased energy metabolism, which may allow astrocytes to provide a concerted response to increased local energy needs in the brain
Our lab is involved in the development, improvement, or implementation of tools in optical microscopy and associated fields, such as UV flash photolysis and image analysis/processing. These activities constitute a important part of our work and are being performed in the framework of the technological developments of the Cellular Imaging Facility

The stress-activated signalling pathways in neuronal death

The MAP kinase pathways include the extracellular signal-regulated kinases (ERKs), the c-Jun amino-terminal kinases (JNKs), and the p38 MAP kinases. Different upstream signals can lead to the activation of different MAPKs. A specific focus of our studies is to understand how MAP kinase signaling pathways modulate neuronal death. In fact many disease states such as Alzheimer, Parkinson, epilepsy, ischemia and brain injury are characterized by strong activation of the stress-activated kinases. The mechanisms underlying the neuronal-death response involve protein kinases, which phosphporylate many substrates including cytosolic and nuclear proteins, culminating in changes in gene expression. A detailed understanding of the molecular processes involved in the control of cell death is required for the design of rational treatments for these diseases. We use cell-penetrating peptides/cationic transporters to prevent neuronal degeneration by inhibiting intracellular key mediators of death signal pathways. We recently show the D-JNKI-1, a cell-permeable peptide designed to inhibit c-Jun-N-terminal kinase action in a very high specific manner, produced astonishing data in in vivo models of neuronal degeneration following ischemia

Molecular mechanisms of chronic pain

Persistent pain associated with peripheral or central nervous system injury / dysfunction is defined as neuropathic pain. The individual consequences of neuropathic pain are devastating - the pain is often intractable - and banal primary injury of peripheral nerve may lead to severe disabilities that not only influence the patient life and psyche, but his or her relatives. Important reorganization of the nervous system occurs and if this may be prevented, the vicious circle of persistent pain inducing individual distress, psychological disturbances, work cessation, and social consequences would be reduced

The goals of our research, using experimental pain models are to identify molecular and structural changes underlying neuropathic pain. Different aspects of pain mechanisms are investigated, from the contribution of ectopic activity to gene modifications in the somatosensory system. During the last years, we focus our research on peripheral ectopic activity investigating voltage-gated sodium channel distribution and effect of long term nerve conduction blocks. Finally, the aim of our laboratory, as a part of the CHUV Department of Anesthesiology and Anesthesiology Pain Center, is to create a bridge between basic science and clinical pain management

Neuronal death : excitotoxicity

For the last six years we have been focusing on excitotoxicity, which means the toxic effect of excessive activation. It is the main cell death mechanism in many clinical conditions including cerebral ischemia, traumatic brain injury, perinatal asphyxia and epilepsy, and it contributes to neuronal death in glaucoma.
1. Neuroprotection by inhibiting the JNK pathway
We have evidence - in vitro and in vivo - that exceptionally strong protection can be obtained against excitotoxicity and ischemic neuronal death by inhibition of the JNK pathway using peptide inhibitors developed by Dr. Christophe Bonny and his group The neuroprotection is accompanied by behavioural sparing. We are currently analysing the cellular mechanisms and evaluating the clinical potential, particularly in relation to cerebral ischemia, perinatal hypoxia and glaucoma

2. Endocytosis and autophagy in excitotoxically stressed neurons
We have evidence that endocytosis and autophagy are involved in certain kinds of cell death, and have recently showed that this is true of excitotoxicity. We are currently studying the significance of these events in the cell death process and are investigating whether the endocytosis can provide a means to target inhibitors specifically into excitotoxically stressed neurons

Exploration des propriétés mécaniques du vivant

Notre travail de recherche concerne la mesure des propriétés mécaniques des cellules et des composants du cytosquelette. Nous travaillons également sur l'étude des forces d'interaction entre les protéines impliquées dans la fusion des vésicules de neurotransmetteurs avec la membrane présynaptique. Ces mesures se font au moyen d'un microscope à force atomique. Le principe de fonctionnement de cet instrument est semblable celui d'un tourne-disque : une fine aiguille fixée l'extrémité d'un levier microscopique balaye l'échantillon et les irrégularités de la surface du spécimen induisent lors du balayage des déplacements verticaux du levier. Ces petits déplacements sont enregistrés et utilisés par un ordinateur pour reconstituer, sur un écran, la topographie de la structure examinée. Pouvant opérer dans des liquides, cet instrument permet l'observation à haute résolution de cellules ou de molécules biologiques dans des conditions proches de leur état naturel. La mesure des propriétés mécaniques se fait en modulant la force avec laquelle la pointe de l'AFM presse sur l'échantillon

Les mécanismes impliqués dans la dérégulation de la cellule bêta pancréatique observée dans la physiopathologie du diabète

Notre groupe s'intéresse aux mécanismes impliqués dans la dérégulation de la cellule bêta pancréatique observée dans la physiopathologie du diabète. L'approche expérimentale comprend l'étude in vitro ou in vivo des mécanismes de survie de la cellule bêta pancréatique. Nous avons identifié de nouveaux mécanismes de dysfonctionnement de la cellule bêta, de nouveaux gènes candidats au diabète humain et des nouvelles cibles thérapeutiques. Les gènes identifiés furent le NPY, MIF, MAPK8IP1 (IB1/JIP-1) qui sont impliqués dans l'homéostasie glucidique et le diabète chez l'homme. L'étude du «trait neuronal» de la cellule bêta pancréatique est un axe important du laboratoire. Ces nouveaux gènes candidats au diabète humain identifiés au niveau de la cellule bêta sont également exprimés au niveau du SNC Des anomalies génétiques de ces gènes (IB1/JIP-1, BETA2, LRP) sont des facteurs de risque au développement de maladies neurodégénératives (Alzheimer) ou du diabète. En dernier lieu, l'intérêt le plus récent du laboratoire est la contribution des lipoprotéines humaines à la fonction des cellules bêta et de la signalisation cellulaire associée. Nous avons démontré l'impact négatif des particules LDL- ou VLDL-lipoprotéines sur la cellule bêta et le rôle critique de facteur anti-apoptotique comme les particules d'HDL-cholesterol. Des études de l'impact de différentes lipoprotéines humaines sur le profil transcriptomique complet de la cellule bêta (Affymetric) sont actuellement en cours. Le laboratoire est à l'interface entre des recherches clinique et génétique effectuées chez le sujet diabétique ou porteur d'une dyslipidémie et la biologie cellulaire et moléculaire avec des partenaires importants du DNF (Prof R. Regazzi et Prof C. Widmann) ou de l'institut de physiologie (Prof Luc Tappy)

Modulation of cerebral cortex development by neurotransmitters

The early expression of neurotransmitters and receptors in the developing brain has brought attention to their potential contribution in modulating neuronal developmental processes. In the recent years, numerous studies have documented the role of several neurotransmitter systems in altering neuronal development at the cellular and the system levels. The cerebral cortex is a well-characterized network of intrinsic neurons and afferent systems synaptically interconnected in complex circuits using a wide range of neurotransmitters and receptors. Its development follows spatio-temporal sequences of neuronal generation, migration, differentiation and maturation, which translate in a laminated morpho-functional organization in the mature cortex.

The main focus of our research projects is the identification and characterization of the developmental processes in the cerebral cortex which are affected by the depletion of monoaminergic neurotransmission. The contribution of monoamine is investigated in parallel in two experimental models: i) organotypic and dissociated cultures of neonatal cortical tissue of rodents, ii) the whole brain of pharmacologically treated or genetically modified rodents. The potential contribution of other neurotransmitter systems such as glutamate has been investigated, in particular via the transduction by its metabotropic receptors. These studies are placed in the context of fundamental and applied neurobiology: the former deals with the regulatory mechanisms of brain development, the latter with the understanding and the management of pathologies with origin in genetic alteration of neurotransmitter metabolism or in secondary effects to drug application

Caractérisation des fonction du clivage de RasGAP et les application thérapeutiques qui peuvent en découler

L'apoptose (ou mort cellulaire programmée) est un phénomène indispensable pour le développement de tout organisme multi-cellulaire. Sans apoptose, le développement du cerveau et du système immunitaire ne pourrait par exemple pas s'effectuer. L'apoptose est déclenchée lorsque des protéases de la famille des caspases sont activées. Afin de mieux comprendre les mécanismes moléculaires régissant l'apoptose, nous étudions le rôle du clivage de certains substrats de caspases. Nous nous intéressons en particulier à une protéine nommée RasGAP qui est une "GTPase-activating protein" spécifique pour Ras. Nous déterminons actuellement comment les fragments de RasGAP générés par les caspases régulent l'apoptose. Nos données indiquent que le fragment N-terminal de RasGAP (appelé fragment N) est, paradoxalement, un inhibiteur de la mort cellulaire. De récentes évidences montrent que les caspases peuvent être impliquées lors de processus de différenciation cellulaire. Il est donc possible que lors de ces processus de différenciation, le fragment N inhibe l'apoptose qui serait normalement enclenchée afin de permettre aux caspases d'exercer d'autres fonctions que l'induction de l'apoptose. Une partie de nos efforts est maintenant consacrée à la caractérisation moléculaire des mécanismes permettant au fragment N d'exercer ses fonctions de protection de la cellule

Comme une mort inappropriée des cellules bêta dans les ilôts de Langerhans du pancréas conduit au diabète, nous avons postulé que l'expression du fragment N dans ces cellules les rendrait plus résistantes et leur permettrait de survivre plus longtemps. Nous avons récemment vérifié que ce concept était valide dans des systèmes de culture in vitro. Nous allons tester maintenant si le fragment N protège aussi des souris de la survenue de diabète

En parallèle, nous étudions les propriétés d'un autre fragment de RasGAP, appelé N2, qui a la capacité de sensibiliser les cellules cancéreuses, mais pas les cellules saines, aux médicaments anti-tumoraux. Nous avons

Computer assisted morphometric data acquisition, processing and analysis

1. Quantitative analysis of pathological hallmarks in neurodegenerative diseases
2. Stereological estimations on neuronal populations
3. Object segmentation and modelisation in a multidimensional neurobiological space

Molecular mechanisms of hormone and neurotransmitter release

Our group has identified several proteins that are associated with the membrane of insulin-containing secretory granules or with the plasma membrane of pancreatic ß-cells. Using cell and molecular biology techniques we were able to demonstrate their involvement in the control of exocytosis. Recently, we focused our attention on Rab GTPases, a large family of proteins that plays a key role in governing the transport and fusion of secretory vesicles in eukaryotic cells. Rab3 and Rab27, two members of this family are associated with secretory granules of pancreatic ß-cells and participate in the fine-tuning of insulin release. Our goal is to assess the respective role of these Rab GTPases in the secretory process of pancreatic ß-cells and to clarify the contribution of their binding partners RIM (Rab3 Interacting Molecule), Granuphilin/Slp4, Slac2-c/MyRIP and Noc2. Our studies take advantage of the possibilities offered by RNA interference, a recently discovered process that allows specific silencing of genes. In the diabetic state, long term exposures to elevated glucose and lipid concentrations have deleterious effects on pancreatic b-cells and leads to loss of specific phenotypic traits such as glucose stimulated insulin secretion. We are currently investigating the effect of glucose on the expression of the proteins involved in insulin exocytosis. In addition, we are assessing the role of a newly discovered class of small non coding RNAs called microRNAs in the maintenance of specific phenotypic traits of b-cell such as insulin production and secretion

The function of cytoskeletal proteins during development and aging of neuronal cells

A major interest is to define the function of cytoskeletal proteins during development and aging of neuronal cells, and to identify the means how a structural stability and plasticity between the different cytoskeletal structures is obtained. Specifically, to study nature and function of cytoskeletal proteins, determine their relationship to other cellular components during neuronal differentiation and analyse their relationship to neuronal morphogenesis. To find factors which influence the formation of the cytoskeleton or which are able to modulate single components of the cytoskeleton. To explore changes of cytoskeletal structures in various disease states (Alzheimer's disease)

Insulin resistance and insulin signaling

Our main research focus are molecular mechanisms involved in insulin resistance. In particular we are studying the role of nitric oxide in glucose homeostasis and lipid metabolism. In order to do so, we use knock out mice for the endothelial nitric oxide synthase (eNOS), which are not only hypertensive but also insulin resistant and have dyslipidemia. They represent therefore a good model of metabolic syndrome. During an euglycemic hyperinsulinemic clamp, eNOS knock out mice have a significantly decreased glucose uptake. In addition, the lack of eNOS (which is also expressed in insulin target tissues) induces insulin resistance in isolated skeletal muscle indicating that nitric oxide plays a role in the cellular response to the hormone

We are also investigating molecular mechanisms involved in the observed dyslipidemia. We were able to show, that eNOS knock out mice have defective mitochondrial beta oxidation. This defect may contribute to increased triglyceride and free fatty acid levels

We are currently investigating how impaired nitric oxide synthesis may lead to defective beta oxidation in isolated mitochondria. Interestingly, abnormal mitochondrial function in skeletal muscle has been suggested to play a role in insulin resistance in humans

Glia, an active synaptic partner : from physiology to neurodegeneration

Over the past fifteen years, an increasing number of observations have progressively modified the classical view that places glial cells in a subservient position to neurons. Among glial cells of the central nervous system (CNS), oligodendrocytes and microglia are recognized since long time to play unique, specialized functions: myelination and host defence, respectively. In contrast, the role of astrocytes has long remained far more enigmatic. Initially considered as the brain glue, just a scaffold, inert but necessary for neuronal distribution and interactions, astrocytes have first evolved to the status of support cells, necessary to assure optimal neuronal functioning. The developments of the last few years have revealed however new, surprising functions, including the control of synapse formation and function, of adult neurogenesis and of the brain vascular tone. One reason why these active properties of astrocytes have remained so long in the dark is the difference in the excitability mechanisms of these cells with respect to neurons. Until recently the electrical language of neurons was thought to be the only form of information encoding in the brain. Since astrocytes do not generate action potentials they were considered non-excitable and thus unable to communicate. The identification of a non-electrical excitability of the astrocytes has expanded the complexity of brain communication to an integrated network of both synaptic and non-synaptic routes

The recognition that astrocytes are organized in separate territories and possess active properties, notably competence for regulated release of "gliotransmitters", including glutamate, has opened the way to the understanding of the new astrocyte functions. Today astrocytes are envisaged as local communication elements of the brain, able to generate a variety of regulatory signals and to bridge structures (from neuronal to vascular, for instance) and networks otherwise disconnected from each other, playing specific, essential roles both in physiology

Role of thyroid hormones and their receptors in peripheral nerve regeneration

Peripheral nerve injuries cause disability because of incomplete recovery of function despite optimal surgical treatment. Therefore, the study of the induction and enhancement of peripheral nerve regeneration has become the research aim for many investigators. Experimental models of peripheral nerve injury in animals revealed that relative success in re-establishing functionally appropriate connections in adult mammals depends on the combined effects of a number of neurotrophic factors, extracellular matrix and hormones
It is widely agreed that thyroid hormones are one of the most important physiological regulators of mammalian nervous system development and maturation. Several studies report that thyroidectomy or administration of antithyroid drugs to newborn rats result in a failure of growth and maturation of various areas in the brain. In the peripheral nervous system, the major consequence of thyroid deficiency in the neonatal rat is a reduction in the number of myelinated fibers and a delay in the increase of their axon diameter in sciatic nerve Furthermore, neonatal hypothyroidism affects the growth of non- myelinated axons and their associated Schwann cells. Thyroid hormones, which are required for the development and maturation of nervous system, could be one of several factors which are involved in nerve regeneration
The major goal of our research is to study the effect of local administration of thyroid hormone (T3) on the regeneration of transected sciatic nerve. Since the action of thyroid hormone on responsive cells is mediated through nuclear receptors, thus in the first step we focused our effort on the detection of T3 receptors in the target tissues. Then the using of silicone tubes allows to demonstrate that the local administration of thyroid hormones at the level of transected rat sciatic nerve reduce the loss of axotomized sensory neurons, enhance peripheral nerve

Organisation and plasticity within the somatosensory cortex

The interest of our research group is to discover the mechanisms by which sensory experience shapes cortical circuitry. Our studies are focussed on the whisker-to-barrel pathway of the mouse, a part of the somatosensory system that we analyse with anatomical and physiological methods.

MAPK pathways components and regulators

The general aim of our laboratory is to understand the role of signaling proteins in apoptosis and other cellular responses. The signalling proteins we focus on are involved in the regulation of mitogen activated protein kinase (MAPK) pathways. Three main avenues of investigations are currently being pursued in the laboratory:

1) Role of the cleavage of signalling proteins by caspases during apoptosis
2) Regulation of MAPK expression levels by scaffold proteins
3) Characterization of the intracellular signals induced by lipoproteins

Competences

Biochimie

Biologie moléculaire

Electrophysiologie sur tranches

Analyse d'images

Microscopie TIRF, optique, confocale, électronique, à force atomique, 2-photons in vitro & in vivo, à onde évanescente

Immunocytochimie

Traçage neuronal

Culture cellulaire et organotypique

Animaux transgéniques

Animations par ordinateur

Microchirurgie

Expression de protéines recombinantes par transfection de vecteurs viraux

Fluorescent biosensors

Etudes comportementales chez le rongeur

Dynamic cellular imaging coupled to electrophysiology

Modèles animaux de pathologies humaines

Dosages spectro-fluorométriques

Patch-champ sur cellules dissociées et en culture

Photolyse "2-photons" de molécules cagées

RT-PCR quantitative, sur cellule unique

Analyse du métabolisme par autoradiographie du 2-désoxyglucose

RIA

Reconstruction 3D

Transfection cellulaire

Isolements d'ilôts pancréatiques