Institute Of Neurobiologie Alfred Fessard

Gif-sur-Yvette, France

Institute Of Neurobiologie Alfred Fessard

Gif-sur-Yvette, France
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Placais P.-Y.,Neurobiology Unit | Trannoy S.,Neurobiology Unit | Isabel G.,Neurobiology Unit | Isabel G.,University Paul Sabatier | And 9 more authors.
Nature Neuroscience | Year: 2012

A fundamental duty of any efficient memory system is to prevent long-lasting storage of poorly relevant information. However, little is known about dedicated mechanisms that appropriately trigger production of long-term memory (LTM). We examined the role of Drosophila dopaminergic neurons in the control of LTM formation and found that they act as a switch between two exclusive consolidation pathways leading to LTM or anesthesia-resistant memory (ARM). Blockade, after aversive olfactory conditioning, of three pairs of dopaminergic neurons projecting on mushroom bodies, the olfactory memory center, enhanced ARM, whereas their overactivation conversely impaired ARM. Notably, blockade of these neurons during the intertrial intervals of a spaced training precluded LTM formation. Two pairs of these dopaminergic neurons displayed sustained calcium oscillations in naive flies. Oscillations were weakened by ARM-inducing massed training and were enhanced during LTM formation. Our results indicate that oscillations of two pairs of dopaminergic neurons control ARM levels and gate LTM. © 2012 Nature America, Inc. All rights reserved.

Del Negro C.A.,University of California at Los Angeles | Hayes J.A.,College of William and Mary | Pace R.W.,College of William and Mary | Brush B.R.,University of California at Los Angeles | And 2 more authors.
Progress in Brain Research | Year: 2010

Breathing, chewing, and walking are critical life-sustaining behaviors in mammals that consist essentially of simple rhythmic movements. Breathing movements in particular involve the diaphragm, thorax, and airways but emanate from a network in the lower brain stem. This network can be studied in reduced preparations in vitro and using simplified mathematical models that make testable predictions. An iterative approach that employs both in vitro and in silico models argues against canonical mechanisms for respiratory rhythm in neonatal rodents that involve reciprocal inhibition and pacemaker properties. We present an alternative model in which emergent network properties play a rhythmogenic role. Specifically, we show evidence that synaptically activated burst-generating conductances-which are only available in the context of network activity-engender robust periodic bursts in respiratory neurons. Because the cellular burst-generating mechanism is linked to network synaptic drive we dub this type of system a group pacemaker. © 2010 Elsevier B.V.

Del Negro C.A.,College of William and Mary | Del Negro C.A.,Institute Of Neurobiologie Alfred Fessard | Hayes J.A.,College of William and Mary | Hayes J.A.,Institute Of Neurobiologie Alfred Fessard | Rekling J.C.,Panum Institute
Journal of Neuroscience | Year: 2011

Medullary interneurons of the preBötzinger complex assemble excitatory networks that produce inspiratory-related neural rhythms, but the importance of somatodendritic conductances in rhythm generation is still incompletely understood. Synaptic input may cause Ca2+ accumulation postsynaptically to evoke a Ca2+-activated inward current that contributes to inspiratory burst generation. We measured Ca2+ transients by two-photon imaging dendrites while recording neuronal somata electrophysiologically. Dendritic Ca2+ accumulation frequently precedes inspiratory bursts, particularly at recording sites 50 -300 μm distal from the soma. Preinspiratory Ca2+ transients occur in hotspots, not ubiquitously, in dendrites. Ca2+ activity propagates orthodromically toward the soma (and antidromically to more distal regions of the dendrite) at rapid rates (300 -700 μm/s). These high propagation rates suggest that dendritic Ca2+ activates an inward current to electrotonically depolarize the soma, rather than propagate as a regenerative Ca2+ wave. These data provide new evidence that respiratory rhythmogenesis may depend on dendritic burst-generating conductances activated in the context of network activity. Copyright©2011 the authors.

Araoz R.,Institute Of Neurobiologie Alfred Fessard | Servent D.,French Atomic Energy Commission | Molgoi J.,Institute Of Neurobiologie Alfred Fessard | Iorga B.I.,CNRS Natural Product Chemistry Institute | And 5 more authors.
Journal of the American Chemical Society | Year: 2011

Pinnatoxins belong to an emerging class of potent marine toxins of the cyclic imine group. Detailed studies of their biological effects have been impeded by unavailability of the complex natural product from natural sources. This work describes the development of a robust, scalable synthetic sequence relying on a convergent strategy that delivered a sufficient amount of the toxin for detailed biological studies and its commercialization for use by other research groups and regulatory agencies. A central transformation in the synthesis is the highly diastereoselective Ireland-Claisen rearrangement of a complex α,α-disubstituted allylic ester based on a unique mode for stereoselective enolization through a chirality match between the substrate and the lithium amide base. With synthetic pinnatoxin A, a detailed study has been performed that provides conclusive evidence for its mode of action as a potent inhibitor of nicotinic acetylcholine receptors selective for the human neuronal α7 subtype. The comprehensive electrophysiological, biochemical, and computational studies support the view that the spiroimine subunit of pinnatoxins is critical for blocking nicotinic acetylcholine receptor subtypes, as evidenced by analyzing the effect of a synthetic analogue of pinnatoxin A containing an open form of the imine ring. Our studies have paved the way for the production of certified standards to be used for mass-spectrometric determination of these toxins in marine matrices and for the development of tests to detect these toxins in contaminated shellfish. © 2011 American Chemical Society.

Forstera B.,University of Concepción | Castro P.A.,Católica del Norte University | Moraga-Cid G.,Institute Of Neurobiologie Alfred Fessard | Aguayo L.G.,University of Concepción
Frontiers in Cellular Neuroscience | Year: 2016

In recent years there has been an increase in the understanding of ethanol actions on the type A γ-aminobutyric acid chloride channel (GABAAR), a member of the pentameric ligand gated ion channels (pLGICs). However, the mechanism by which ethanol potentiates the complex is still not fully understood and a number of publications have shown contradictory results. Thus many questions still remain unresolved requiring further studies for a better comprehension of this effect. The present review concentrates on the involvement of GABAAR in the acute actions of ethanol and specifically focuses on the immediate, direct or indirect, synaptic and extra-synaptic modulatory effects. To elaborate on the immediate, direct modulation of GABAAR by acute ethanol exposure, electrophysiological studies investigating the importance of different subunits, and data from receptor mutants will be examined. We will also discuss the nature of the putative binding sites for ethanol based on structural data obtained from other members of the pLGICs family. Finally, we will briefly highlight the glycine gated chloride channel (GlyR), another member of the pLGIC family, as a suitable target for the development of new pharmacological tools. © 2016 Förstera, Castro, Moraga-Cid and Aguayo.

Castro-Gonzalez C.,Technical University of Madrid | Castro-Gonzalez C.,CIBER ISCIII | Ledesma-Carbayo M.J.,Technical University of Madrid | Ledesma-Carbayo M.J.,CIBER ISCIII | And 3 more authors.
Birth Defects Research Part C - Embryo Today: Reviews | Year: 2012

Digital atlases of animal development provide a quantitative description of morphogenesis, opening the path toward processes modeling. Prototypic atlases offer a data integration framework where to gather information from cohorts of individuals with phenotypic variability. Relevant information for further theoretical reconstruction includes measurements in time and space for cell behaviors and gene expression. The latter as well as data integration in a prototypic model, rely on image processing strategies. Developing the tools to integrate and analyze biological multidimensional data are highly relevant for assessing chemical toxicity or performing drugs preclinical testing. This article surveys some of the most prominent efforts to assemble these prototypes, categorizes them according to salient criteria and discusses the key questions in the field and the future challenges toward the reconstruction of multiscale dynamics in model organisms. © 2012 Wiley Periodicals, Inc..

Roude D.,Rennes Institute of Physics | Recher G.,Equipe SCANING | Recher G.,Institute Of Neurobiologie Alfred Fessard | Bellanger J.-J.,CNRS Signal and Image Processing Laboratory | And 3 more authors.
Biophysical Journal | Year: 2011

A theoretical far-field second harmonic generation (SHG) imaging radiation pattern is calculated for muscular myosin taking into account both Gouy effect and light diffraction under high focusing excitation. Theoretical analysis, in agreement with experimental results obtained on healthy Xenopus muscles, shows that the increase on intensity at the middle of the sarcomeric SHG intensity pattern is generated by an off-axis constructive interference related to the specific antipolar distribution of myosin molecules within the sarcomere. The best fit of the experimental sarcomeric SHG intensity pattern was obtained with an estimated size of antiparallel, intrathick filaments' packing-width of 115 ± 25 nm localized at the M-band. During proteolysis, experimental sarcomeric SHG intensity pattern exhibits decrease on intensity at the center of the sarcomere. An effective intra- and interthick filaments centrosymmetry of 320 ± 25 nm, in agreement with ultrastructural disorganization observed at the electron microscopy level, was necessary to fit the experimental sarcomeric SHG intensity pattern. Our results show that sarcomeric SHG intensity pattern is very sensitive to misalignment of thick filaments and highlights the potential usefulness of SHG microscopy to diagnose proteolysis-induced muscular disorders. © 2011 Biophysical Society.

Stivala C.E.,Stanford University | Benoit E.,Institute Of Neurobiologie Alfred Fessard | Araoz R.,Institute Of Neurobiologie Alfred Fessard | Servent D.,French Atomic Energy Commission | And 3 more authors.
Natural Product Reports | Year: 2015

Covering: up to August 2014 From a small group of exotic compounds isolated only two decades ago, Cyclic Imine (CI) toxins have become a major class of marine toxins with global distribution. Their distinct chemical structure, biological mechanism of action, and intricate chemistry ensures that CI toxins will continue to be the subject of fascinating fundamental studies in the broad fields of chemistry, chemical biology, and toxicology. The worldwide occurrence of potent CI toxins in marine environments, their accumulation in shellfish, and chemical stability are important considerations in assessing risk factors for human health. This review article aims to provide an account of chemistry, biology, and toxicology of CI toxins from their discovery to the present day. This journal is © The Royal Society of Chemistry.

Delloye-Bourgeois C.,University of Lyon | Rama N.,University of Lyon | Brito J.,Institute Of Neurobiologie Alfred Fessard | Brito J.,Federal University of Rio de Janeiro | And 2 more authors.
Biochemical and Biophysical Research Communications | Year: 2014

Cell-adhesion molecule-related/Downregulated by Oncogenes (CDO or CDON) was identified as a receptor for the classic morphogen Sonic Hedgehog (SHH). It has been shown that, in cell culture, CDO also behaves as a SHH dependence receptor: CDO actively triggers apoptosis in absence of SHH via a proteolytic cleavage in CDO intracellular domain. We present evidence that CDO is also pro-apoptotic in the developing neural tube where SHH is known to act as a survival factor. SHH, produced by the ventral foregut endoderm, was shown to promote survival of facial neural crest cells (NCCs) that colonize the first branchial arch (BA1). We show here that the survival activity of SHH on neural crest cells is due to SHH-mediated inhibition of CDO pro-apoptotic activity. Silencing of CDO rescued NCCs from apoptosis observed upon SHH inhibition in the ventral foregut endoderm. Thus, the pair SHH/dependence receptor CDO may play an important role in neural crest cell survival during the formation of the first branchial arch. © 2014 Elsevier Inc. All rights reserved.

Bery A.,Institute Of Neurobiologie Alfred Fessard | Martynoga B.,MRC NIMR | Guillemot F.,MRC NIMR | Joly J.-S.,Institute Of Neurobiologie Alfred Fessard | Retaux S.,Institute Of Neurobiologie Alfred Fessard
Cerebral Cortex | Year: 2014

We aimed to identify cis-regulatory elements that control gene expression in progenitors of the cerebral cortex. A list of 975 putative enhancers were retrieved from a ChIP-Seq experiment performed in NS5 mouse stem cells with antibodies to Sox2, Brn2/Pou3f2, or Brn1/Pou3f3. Through a selection pipeline including gene ontology and expression pattern, we reduced the number of candidate enhancer sequences to 20. Ex vivo electroporation of green fluorescent pProtein (GFP) reporter constructs in the telencephalon of mouse embryos showed that 35% of the 20 selected candidate sequences displayed enhancer activity in the developing cortex at E13.5. In silico transcription factor binding site (TFBS) searches and mutagenesis experiments showed that enhancer activity is related to the presence of Sox/Pou TFBS pairs in the sequence. Comparative genomic analyses showed that enhancer activity is not related to the evolutionary conservation of the sequence. Finally, the combination of in utero electroporation of GFP reporter constructs with immunostaining for Tbr2 (basal progenitor marker) and phospho-histoneH3 (mitotic activity marker) demonstrated that each enhancer is specifically active in precise subpopulations of progenitors in the cortical germinal zone, highlighting the heterogeneity of these progenitors in terms of cis-regulation. © The Author 2013.

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