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Conférence mensuelle - Juan Burrone, Axe développementNeurons, synapses and the axon initial segment: location matters

Abstract :

Juan Burrone invité pour l'axe développement   par Laurent Groc et Mireille Montcouquiol

Burrone Group

  Our lab is interested in understanding how neurons in the brain integrate synaptic information to fire an action potential and how this is modified by chronic alterations in network activity. In the past, our work has focused on two crucial sites for neuronal information processing and integration: the synapse and the axon initial segment (AIS). Both sites undergo important structural and functional rearrangements in response to chronic activity changes, together controlling the input-output function of a neuron and so allowing neuronal networks to function efficiently.

Here, we describe a structural form of activity-dependent plasticity that changes the location of the AIS, in turn modulating neuronal output in hippocampal neurons.  More importantly we examine what happens to the axo-axonic GABAergic synapses that form onto the AIS and use a computational model to establish the functional consequences of this plasticity on neuronal output. We then move upstream of the AIS to focus on how excitatory synaptic inputs are distributed along the large dendritic tree of a hippocampal neuron. We use different imaging techniques to obtain measures of the structure and function of both presynaptic and postsynaptic compartments and map their distribution along tapering dendrites. We find that the size of synapses and the activation of functional NMDARs are not randomly distributed along an arbour, but show a clear bias, such that smaller synapses with equal number of NMDARs are found towards thin dendritic tip ends. This distribution in synapse properties is ideally suited to non-linear integration in distal dendrites, a feature that allows coincident activation of clustered inputs to be amplified when measured at the AIS.

Selected publications

Activity-dependent mismatch between axo-axonic synapses and the axon initial segment controls neuronal output. Wefelmeyer W, Cattaert D, Burrone J. Proc Natl Acad Sci U S A. 2015 Aug 4;112(31):9757-62. doi: 10.1073/pnas.1502902112. Epub 2015 Jul 20.

Spontaneous Neurotransmitter Release Shapes Dendritic Arbors via Long-Range Activation of NMDA Receptors. Andreae LC, Burrone J. Cell Rep. 2015 Feb 12. pii: S2211-1247(15)00057-1. doi: 10.1016/j.celrep.2015.01.032. [Epub ahead of print]

Optical control of muscle function by transplantation of stem cell-derived motor neurons in mice. Bryson JB, Machado CB, Crossley M, Stevenson D, Bros-Facer V, Burrone J, Greensmith L, Lieberam I. Science. 2014 Apr 4;344(6179):94-7. doi: 10.1126/science.1248523.

The role of neuronal activity and transmitter release on synapse formation. Andreae LC, Burrone J. Curr Opin Neurobiol. 2014 Aug;27:47-52. doi: 10.1016/j.conb.2014.02.008. Epub 2014 Mar 13. Review.

 Independent vesicle pools underlie different modes of release during neuronal development. Andreae LC, Fredj NB, Burrone J. J Neurosci. 2012 Feb 1;32(5):1867-74. doi: 10.1523/JNEUROSCI.5181-11.2012.

 Neuronal activity drives matching of pre- and postsynaptic function during synapse maturation. Kay L, Humphreys L, Eickholt BJ, Burrone J. Nat Neurosci. 2011 Jun;14(6):688-90. doi: 10.1038/nn.2826. Epub 2011 May 1.

 Activity-dependent relocation of the axon initial segment fine-tunes neuronal excitability. Grubb MS, Burrone J. Nature. 2010 Jun 24;465(7301):1070-4. doi: 10.1038/nature09160. Epub 2010 Jun 13.

Mireille Montcouquiol (Mireille.montcouquiol @ inserm.fr)

Speaker+pizza

Discussion avec le conférencier autour d'une pizza offerte si l'étudiant s'inscrit rapidement auprès de : elodie.penicaud@u-bordeaux.fr