Neurocentre Magendie



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2006, Ph.D. 'Biology, Medicine and Health', option Neurosciences; University of Caen, UMR CNRS 6185, Centre CYCERON (France)
January 2007 to June 2012, Postdoc in François Guillemot’s lab, National Institute for Medical Research (London, UK)

Expertise: neurogenesis, RhoGTPases, neuronal development, Rnd proteins

21 publication(s) depuis Février 2005:

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Les IF indiqués ont été collectés par le Web of Sciences en

06/07/2017 | elife   IF 7.7
Physiological and pathophysiological control of synaptic GluN2B-NMDA receptors by the C-terminal domain of amyloid precursor protein.
Pousinha PA, Mouska X, Raymond EF, Gwizdek C, Dhib G, Poupon-Silvestre G, Zaragosi LE, Giudici C, Bethus I, Pacary E, Willem M, Marie H

The amyloid precursor protein (APP) harbors physiological roles at synapses and is central to Alzheimer's disease (AD) pathogenesis. Evidence suggests that APP intracellular domain (AICD) could regulate synapse function, but the underlying molecular mechanisms remain unknown. We addressed AICD actions at synapses, per se, combining in-vivo AICD expression, ex-vivo AICD delivery or APP knock-down by in utero electroporation of shRNAs with whole-cell electrophysiology. We report a critical physiological role of AICD in controlling GluN2B-containing NMDA receptors (NMDARs) at immature excitatory synapses, via a transcription-dependent mechanism. We further show that AICD increase in mature neurons, as reported in AD, alters synaptic NMDAR composition to an immature-like GluN2B-rich profile. This disrupts synaptic signal integration, via over-activation of SK channels, and synapse plasticity, phenotypes rescued by GluN2B antagonism. We provide a new physiological role for AICD, which becomes pathological upon AICD increase in mature neurons. Thus, AICD could contribute to AD synaptic failure.

03/10/2016 | curr protoc neurosci
Cerebral Cortex Electroporation to Study Projection Neuron Migration.
Pacary E, Guillemot F

Brain electroporation is a rapid and powerful approach to study neuronal development. In particular, this technique has become a method of choice for studying the process of radial migration of projection neurons in the embryonic cerebral cortex. This method has considerably helped to describe in detail the different steps of radial migration and to characterize the molecular mechanisms controlling this process. Delineating the complexities of neuronal migration is critical to our understanding not only of normal cerebral cortex formation but also of neurodevelopmental disorders resulting from neuronal migration defects. Here, we describe in detail the protocols to perform in utero or ex vivo electroporation of progenitor cells in the ventricular zone of the cerebral cortex with the aim of studying the process of radial migration of projection neurons during embryonic development. (c) 2016 by John Wiley & Sons, Inc.

2015 | front neurosci   IF 3.6
Function and regulation of Rnd proteins in cortical projection neuron migration.
Azzarelli R, Guillemot F, Pacary E

The mammalian cerebral cortex contains a high variety of neuronal subtypes that acquire precise spatial locations and form long or short-range connections to establish functional neuronal circuits. During embryonic development, cortical projection neurons are generated in the areas lining the lateral ventricles and they subsequently undergo radial migration to reach the position of their final maturation within the cortical plate. The control of the neuroblast migratory behavior and the coordination of the migration process with other neurogenic events such as cell cycle exit, differentiation and final maturation are crucial to normal brain development. Among the key regulators of cortical neuron migration, the small GTP binding proteins of the Rho family and the atypical Rnd members play important roles in integrating intracellular signaling pathways into changes in cytoskeletal dynamics and motility behavior. Here we review the role of Rnd proteins during cortical neuronal migration and we discuss both the upstream mechanisms that regulate Rnd protein activity and the downstream molecular pathways that mediate Rnd effects on cell cytoskeleton.

2014 | Methods Mol Biol   IF 0.8
In utero electroporation to study mouse brain development.
Pacary E , Guillemot F

In utero electroporation is a rapid and powerful technique to study the development of many brain regions. This approach presents several advantages over other methods to study specific steps of brain development in vivo, from proliferation to synaptic integration. Here, we describe in detail the individual steps necessary to carry out the technique. We also highlight the variations that can be implemented to target different cerebral structures and to study specific steps of development.

2014 | Front Cell Neurosci   IF 4.6
Regulation of cerebral cortex development by Rho GTPases: insights from in vivo studies.
Azzarelli R, Kerloch T, Pacary E

The cerebral cortex is the site of higher human cognitive and motor functions. Histologically, it is organized into six horizontal layers, each containing unique populations of molecularly and functionally distinct excitatory projection neurons and inhibitory interneurons. The stereotyped cellular distribution of cortical neurons is crucial for the formation of functional neural circuits and it is predominantly established during embryonic development. Cortical neuron development is a multiphasic process characterized by sequential steps of neural progenitor proliferation, cell cycle exit, neuroblast migration and neuronal differentiation. This series of events requires an extensive and dynamic remodeling of the cell cytoskeleton at each step of the process. As major regulators of the cytoskeleton, the family of small Rho GTPases has been shown to play essential functions in cerebral cortex development. Here we review in vivo findings that support the contribution of Rho GTPases to cortical projection neuron development and we address their involvement in the etiology of cerebral cortex malformations.

2014 | Nat Commun   IF 12.1
An antagonistic interaction between PlexinB2 and Rnd3 controls RhoA activity and cortical neuron migration.
Azzarelli R , Pacary E , Garg R , Garcez P , van den Berg D , Riou P , Ridley AJ , Friedel RH , Parsons M , Guillemot F

A transcriptional programme initiated by the proneural factors Neurog2 and Ascl1 controls successive steps of neurogenesis in the embryonic cerebral cortex. Previous work has shown that proneural factors also confer a migratory behaviour to cortical neurons by inducing the expression of the small GTP-binding proteins such as Rnd2 and Rnd3. However, the directionality of radial migration suggests that migrating neurons also respond to extracellular signal-regulated pathways. Here we show that the Plexin B2 receptor interacts physically and functionally with Rnd3 and stimulates RhoA activity in migrating cortical neurons. Plexin B2 competes with p190RhoGAP for binding to Rnd3, thus blocking the Rnd3-mediated inhibition of RhoA and also recruits RhoGEFs to directly stimulate RhoA activity. Thus, an interaction between the cell-extrinsic Plexin signalling pathway and the cell-intrinsic Ascl1-Rnd3 pathway determines the level of RhoA activity appropriate for cortical neuron migration.

10/07/2013 | Nat Commun   IF 12.1
Amplification of progenitors in the mammalian telencephalon includes a new radial glial cell type.
Pilz GA , Shitamukai A , Reillo I , Pacary E , Schwausch J , Stahl R , Ninkovic J , Snippert HJ , Clevers H , Godinho L , Guillemot F , Borrell V , Matsuzaki F , Gotz M

The mechanisms governing the expansion of neuron number in specific brain regions are still poorly understood. Enlarged neuron numbers in different species are often anticipated by increased numbers of progenitors dividing in the subventricular zone. Here we present live imaging analysis of radial glial cells and their progeny in the ventral telencephalon, the region with the largest subventricular zone in the murine brain during neurogenesis. We observe lineage amplification by a new type of progenitor, including bipolar radial glial cells dividing at subapical positions and generating further proliferating progeny. The frequency of this new type of progenitor is increased not only in larger clones of the mouse lateral ganglionic eminence but also in cerebral cortices of gyrated species, and upon inducing gyrification in the murine cerebral cortex. This implies key roles of this new type of radial glia in ontogeny and phylogeny.

The generation of neurons by neural stem cells is a highly choreographed process that requires extensive and dynamic remodelling of the cytoskeleton at each step of the process. The atypical RhoGTPase Rnd3 is expressed by progenitors in the embryonic brain but its role in early steps of neurogenesis has not been addressed. Here we show that silencing Rnd3 in the embryonic cerebral cortex interferes with the interkinetic nuclear migration of radial glial stem cells, disrupts their apical attachment and modifies the orientation of their cleavage plane. These defects are rescued by co-expression of a constitutively active form of cofilin, demonstrating that Rnd3-mediated disassembly of actin filaments coordinates the cellular behaviour of radial glial. Rnd3 also limits the divisions of basal progenitors via a distinct mechanism involving the suppression of cyclin D1 translation. Interestingly, although Rnd3 expression is controlled transcriptionally by Ascl1, this proneural factor is itself required in radial glial progenitors only for proper orientation of cell divisions.

26/04/2012 | Neuron   IF 14
Crucial first steps: the transcriptional control of neuron delamination.
Pacary E , Martynoga B , Guillemot F

A crucial event in the birth of a neuron is the detachment of its apical process from the neuroepithelium. In this issue of Neuron, Rousso et al. (2012) show that repression of N-cadherin by Foxp transcription factors disrupts apical adherens junctions and triggers neurogenesis.

2012 | J Vis Exp   IF 1.2
Visualization and genetic manipulation of dendrites and spines in the mouse cerebral cortex and hippocampus using in utero electroporation.
Pacary E, Haas MA, Wildner H, Azzarelli R, Bell DM, Abrous DN, Guillemot F

In utero electroporation (IUE) has become a powerful technique to study the development of different regions of the embryonic nervous system (1-5). To date this tool has been widely used to study the regulation of cellular proliferation, differentiation and neuronal migration especially in the developing cerebral cortex (6-8). Here we detail our protocol to electroporate in utero the cerebral cortex and the hippocampus and provide evidence that this approach can be used to study dendrites and spines in these two cerebral regions. Visualization and manipulation of neurons in primary cultures have contributed to a better understanding of the processes involved in dendrite, spine and synapse development. However neurons growing in vitro are not exposed to all the physiological cues that can affect dendrite and/or spine formation and maintenance during normal development. Our knowledge of dendrite and spine structures in vivo in wild-type or mutant mice comes mostly from observations using the Golgi-Cox method( 9). However, Golgi staining is considered to be unpredictable. Indeed, groups of nerve cells and fiber tracts are labeled randomly, with particular areas often appearing completely stained while adjacent areas are devoid of staining. Recent studies have shown that IUE of fluorescent constructs represents an attractive alternative method to study dendrites, spines as well as synapses in mutant / wild-type mice (10-11) (Figure 1A). Moreover in comparison to the generation of mouse knockouts, IUE represents a rapid approach to perform gain and loss of function studies in specific population of cells during a specific time window. In addition, IUE has been successfully used with inducible gene expression or inducible RNAi approaches to refine the temporal control over the expression of a gene or shRNA (12). These advantages of IUE have thus opened new dimensions to study the effect of gene expression/suppression on dendrites and spines not only in specific cerebral structures (Figure 1B) but also at a specific time point of development (Figure 1C). Finally, IUE provides a useful tool to identify functional interactions between genes involved in dendrite, spine and/or synapse development. Indeed, in contrast to other gene transfer methods such as virus, it is straightforward to combine multiple RNAi or transgenes in the same population of cells. In summary, IUE is a powerful method that has already contributed to the characterization of molecular mechanisms underlying brain function and disease and it should also be useful in the study of dendrites and spines.