PhD: Bernat Gonzalez i Llinares

Presynaptic Mechanisms of Short-Term Plasticity at Hippocampal Mossy Fiber Synapses

December 17th, 2014

The hippocampal mossy fiber is characterized by its particular morphology, distinct synaptic transmission and presynaptic plasticity. Moreover, this synapse has been called “teacher” or “detonator” for its proposed functional role in episodic memory encoding. Nevertheless, the molecular mechanisms underlying its specific functional properties remain elusive. This work is composed of two main parts:

1) Phenotyping Hippocampal Mossy Fiber Synapses in VAMP7 KO Mice VAMP7 is a vesicle SNARE of the longin family important in neurite growth during development. In the adult brain, VAMP7 is enriched in a subset of nerve terminals, particularly at the hippocampal mossy fiber. We analyzed VAMP7 function in neurotransmitter release by characterizing basal and evoked transmission at this synapse in KO mice and fully tested hypotheses relevant to short-term plasticity. Loss of VAMP7 has been previously reported not to cause major developmental or neurological deficits (Sato et al., 2011; Danglot et al., 2012). Presynaptic mechanisms of short-term plasticity at the hippocampal mossy fiber also seem unaffected for potential reasons which will be discussed.

2) CA3 Circuits Probed with RABV-Tracing and Paired Recordings We developed a technique to establish paired recordings between connected dentate gyrus granule cells and CA3 pyramidal cells (GC-CA3) in mouse hippocampal organotypic slice cultures. To identify direct presynaptic partners to a defined target CA3 pyramidal cell, we combined single-cell electroporation (SCE) and mono-trans-synaptic tracing based on a pseudotyped, recombinant rabies virus (EnvA pseudotyped RABV ΔG). Using SCE we transfected a single CA3 pyramidal cell per slice with the plasmids encoding: the RABV envelope glycoprotein (RG), a fluorescent reporter, and TVA (the EnvA cognate surface receptor, which has no homologue in mammalian cells). The slices were subsequently infected with EnvA pseudotyped RABV ΔG. After 3-4 days, the RABV mono-trans-synaptic tracing revealed the presynaptic inputs of that single neuron. Then, we were able to establish paired recordings between connected GC-CA3 cells, as well as to quantify the presynaptic partners of the starter CA3 pyramidal cell.

Keywords : Hippocampal Mossy Fiber, Short-Term Plasticity, TI-VAMP/VAMP7 KO mouse, Rabies Virus Tracing, Paired Recordings

Publication in preparation

González i Llinares B., Danglot L., Verhage M., Galli T. and Mulle C. Phenotyping hippocampal mossy fiber synapses in TI-VAMP/VAMP7 KO mice

PhD Committee

  • Olivier THOUMINE 
    Directeur de recherche CNRS – Président
    Professeur Universidad de Sevilla – Rapporteur
  • Richard MILES 
    Directeur de recherche INSERM – Rapporteur
  • ​Lydia DANGLOT​
    ​Chargée de recherche INSERM – Examinatrice​
  • ​​Matthijs VERHAGE
    Professeur VU Amsterdam  – Co-directeur de thèse
  • Christophe MULLE
    Directeur de recherche CNRS  – Directeur de thèse

Thesis supervisors

Christophe MULLE
Directeur de recherche CNRS
Interdisciplinary Institute for Neuroscience
University of Bordeaux

Matthijs Verhage
Dept. of Functional Genomics, Faculty of Earth and Life Sciences (FALW) University Amsterdam (VU)

Last update: 14 April 2018