Les dernières actualités






Séminaire
25/09/2018 14h00
Sophie TRONEL

Lieu: Neurocentre Magendie Seminar room

Soutenance HDR: Sophie Tronel from Abrous's lab will give a presentation entitled 'Etude de la stabilisation de la mémoire'





Team “Neurogenesis and pathophysiology”. Neurocentre Magendie / Bordeaux Neurocampus:

The dentate gyrus (DG) of the hippocampus is one of the few mammalian brain structures where neurogenesis is maintained throughout the lifetime of individuals. Indeed the dentate granule cells (GCs), the main neuronal cell type in the DG, are generated via several distinct phases occurring during late embryogenesis, the early postnatal life, the juvenile period and throughout adulthood. Because of this continuous addition of new cells, the DG appears as a heterogeneous structure composed of different populations of granule neurons. Whether these different populations have similar or distinct structural and functional properties is still a matter of debate. Surprisingly, although most dentate GCs are generated during development, little was known about their properties compared to adult-born neurons. Nevertheless, it was generally admitted that these populations are morphologically indistinguishable once mature. However a detailed and extensive analysis of developmentally-born neurons was lacking for proper comparison.


In this study, we used in vivo electroporation to label dentate GCs generated in mouse embryos (E14.5) or in neonates (P0) and followed their morphological development up to 6 months after birth. Importantly, we highlight for the first time major morphological differences with GCs born during the juvenile period (P21) or during adulthood (P84). Importantly, we also identified different morphological parameters that can be used to predict the birthdate of granule neurons in adult brain sections. In addition, our data indicate that two other poorly studied populations of GCs in the DG, the semilunar and hilar granule cells are generated during the embryonic and the neonatal periods respectively. Thus, our findings provide new insights into the development of the different populations of granule neurons in the DG and open new questions regarding their function in the brain. Indeed, the dendritic tree determines the amount and specificity of inputs a neuron receives and is involved in sophisticated signal processing and neural computation. Consequently, mature dentate GCs born at embryonic, neonatal or adult stages might contribute differently to hippocampal function. Future analyses of the inputs and functional properties of the different populations of GCs using in vivo electroporation might help to address this controversial question.(Pictures : Thomas Kerloch, Nora Abrous, Emilie Pacary)

Dentate Granule Neurons Generated During Perinatal Life Display Distinct Morphological Features Compared With Later-Born Neurons in the Mouse Hippocampus. Thomas Kerloch, Solène Clavreul, Adeline Goron, Djoher Nora Abrous, Emilie Pacary. Cereb Cortex. 2018 Sep 12. doi: 10.1093/cercor/bhy224.




Séminaire
21/09/2018 11h30
Jason Shepherd, University of Utah - Host Anna Beyeler
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Lieu: Amphithéâtre du Centre Broca Nouvelle-Aquitaine

Inter-cellular RNA transfer: a novel role of the neuronal gene Arc which encodes a repurposed retrotransposon protein

The neuronal gene Arc is essential for long-lasting information storage in the mammalian brain. We recently found that Arc self-assembles into virus-like capsids that encapsulate RNA. Endogenous Arc protein is released from neurons in extracellular vesicles that mediate the transfer of Arc mRNA into new target cells. These results show that Arc exhibits similar molecular properties to retroviral Gag proteins. Evolutionary analysis indicates that Arc is derived from a vertebrate lineage of Ty3/gypsy retrotransposons, which are also ancestors to retroviruses. These findings suggest that Gag retroelements have been repurposed during evolution to mediate intercellular communication in the nervous system. Our working model posits that Arc protein is locally translated in dendrites, where it forms a capsid that binds local mRNAs that are transported out of the cell.



Pour plus de détails: http://www.bordeaux-neurocampus.fr/fr/manifestations-scientifiques/seminaires-2018/jason-shepherd.html



L'article Hippocampal CB1 Receptors Control Incidental Associations, une collaboration Bordeaux Neurocampus a fait l'objet d'un abstract video publié sur la chaine de Neuron, à voir ici : https://youtu.be/1qF2NUBylhA





Lieu: Amphi du Centre Broca

Dr. Marloes Henckens from Department of Cognitive Neuroscience, Donders Institute for Brain (Netherlands)'s lab will give a presentation entitled 'The neural signature of trauma susceptibility'

Invitant : Aline Desmedt, PhD , Maitre de Conférence au Neurocentre Magendie, Team Marighetto 'Pathophysiology of declarative memory'

Posttraumatic stress disorder (PTSD) is a psychiatric disorder which can develop after exposure to a traumatic event. Flashbacks, spontaneous recollection and recurrent nightmares of the trauma are amongst the most devastating symptoms of PTSD, through which patients continuously relive their trauma. Interestingly, only a small fraction (8-10%) of all trauma-exposed individuals eventually develops PTSD, whereas the rest is resilient and remains healthy. But how is the vulnerable brain different from the resilient one and when do these differences arise? Understanding the mechanisms behind these inter-individual differences could contribute to new clinical intervention strategies.
The use of a mouse model for PTSD allows us to study the mechanisms underlying relative resilience or susceptibility to PTSD in a longitudinal fashion, under controlled settings, while allowing for more invasive brain measurements. In this model, mice are first exposed to a traumatic event (i.e., severe unpredictable foot shock), followed by a trigger (i.e., mild predictable foot shock) in a different context one day later. Following a week of recovery, eventual development of PTSD-like symptomatology is assessed using a battery of behavioural tests to identify mice resilient and vulnerable to the trauma. Combining this model with functional MRI obtained both before and after trauma exposure, allowed us to study the development of a potential imbalance in neural network function as a consequence of trauma in the PTSD-vulnerable vs resilient brain, as well as the potential presence of neural abnormalities prior to trauma exposure in these animals. To study brain responses to the trauma itself, we used the so-called targeted recombination in active populations (TRAP) mice, in which the injection of tamoxifen opens up a temporal window in which all neurons expressing certain immediate early genes (reflecting neuronal activity), are permanently fluorescently labelled. We injected these animals with tamoxifen just prior to trauma exposure, and again assessed PTSD-symptoms later on. By re-exposing them to the traumatic context just before sacrifice and analysing trauma retrieval-induced neuronal activity by immunohistochemistry, we were moreover able to analyse the storage of the trauma memory into long-term memory. This allowed us to assess whether aberrant storage of the trauma memory could explain the emotional hypermnesia and contextual hypomnesia of the trauma that seem to characterize PTSD patients.


Pour plus de détails: http://www.bordeaux-neurocampus.fr/fr/manifestations-scientifiques/seminaires-2018/marloes-henckens.html



Busquets-Garcia A, Oliveira da Cruz J, Terral G, Pagano Zottola AC, Soria-Gómez E, Contini A, Martin H, Redon B, Varilh M, Ioannidou C, Drago F, Massa F, Fioramonti X, Trifilieff P, Ferreira G*, Marsicano G* (2018).Hippocampal CB1 receptors control incidental associations. Neuron https://doi.org/10.1016/j.neuron.2018.08.014





Le travail des AP du centre a fait l'objet d'une interview publiée dans le N° du mois d'aout de la lettre Objectif Santé & Sécurité de l'Inserm.
Lire l'interview en page 3.





En page 6 du magazine, Émilie décrit ses découvertes sur le rôle de la protéine CaMKII dans la modulation de la migration neuronale. L'article peut être consulté ici : https://fr.calameo.com/read/005154450616c517dbd2a




Info générale
12/07/2018
ANR : et les lauréats 2018 sont...

5 projets de recherches retenus par l'ANR dans le cadre de l'appel à projets générique 2018 (et 4 en liste complémentaire). Bravo aux équipes du centre et en particulier à Nathalie Sans, Daniela Cota, Giovanni Marsicano, Cyril Herry, Cyril Dejean et Xavier Leinekugel. On croise les doigts pour Daniel Voisin, Émilie Pacary, Gwendal Le Masson et Luigi Bellocchio.




Info générale
29/06/2018
Promotions ITA Inserm

Les différentes campagnes de promotion s'achèvent à l'Inserm et la moisson est encore bonne pour nos collègues ITA : Dania Prendin par concours interne, Hélène Doat par la sélection professionnelle, et Mélanie Ginger, Catherine Adane et Jean-Baptiste Bernard à la promotion au choix. Bravo aux 5 lauréats de l'année et à tous ceux qui les ont aidé.