Venue: Centre Broca
Defense in French
Team : Mechanisms of Adaptive Processes in brain circuits (MAP)
IINS
Thesis supervisor: Olivier Thoumine
Title
“Localization, dynamics and nanoscale organization of the synaptic adhesion molecule neuroligin-1”
Abstract
Neuroligins are adhesion molecules essential for the development and function of synapses, and the target of genetic mutations associated with autism spectrum disorders in humans. In this PhD work, I aimed to elucidate the synaptic localization, membrane dynamics, and nanoscale organization of neuroligin-1 (NLGN1).
First, I used overexpression and protein replacement strategies. I demonstrated a significant synaptic residence time of tagged NLGN1, suggesting its stabilization at synapses through multiple extracellular and intracellular interactions.
Next, I used a new knock-in mouse line developed in our team, expressing endogenously tagged NLGN1 (bAP-NLGN1), which allows for its visualization and purification without altering its expression. Through pull-down assays, I showed that native NLGN1 can bind to other isoforms NLGN2 and NLGN3, as well as to PSD-95 and gephyrin, the scaffolding proteins of excitatory and inhibitory synapses, respectively. Using epifluorescence microscopy, I further revealed its localization at both excitatory and inhibitory synapses. Finally, using dSTORM super-resolution imaging, I demonstrated that NLGN1 molecules are organized into nanodomains aligned with presynaptic structures, whose number positively scales with the size of the postsynapse.
These findings provide new insights into the localization and nanoscale organization of endogenous NLGN1, challenging the traditional view that NLGN1 is specific to excitatory synapses. Moreover, the developed knock-in mouse model opens new avenues for studying NLGN1 in more complex systems and in the context of mutations associated with neurodevelopmental disorders.
Keywords
Knock-in mouse, Synapse, Adhesion molecule, Neuroligin, Pull-down, Super-resolution imaging
Publications
- Ducrot C*, Drouet A*, Tessier B, Desquines C, Cloâtre T, Mazzouzi RC, Levet F, Favereaux A, Letellier M, and Thoumine O (2025). High-affinity detection of biotinylated endogenous neuroligin-1 at excitatory and inhibitory synapses using a tagged knock-in mouse. Proc. Natl. Acad. Sci. U.S.A., 3;122(22):e2411669122. doi.org/10.1073/pnas.2411669122
- Szíber Z, Drouet A, Mondin M, Levet F, and Thoumine O (2024). Neuroligin-1 dependent phosphotyrosine signaling in excitatory synapse differentiation. Front. Mol. Neurosci., 17, 1359067. doi.org/10.3389/fnmol.2024.1359067
- Lagardère M*, Drouet A*, Sainlos M, and Thoumine O (2022). High-resolution fluorescence imaging combined with computer simulations to quantitate surface dynamics and nanoscale organization of neuroligin-1 at excitatory synapses. Front. Synaptic Neurosci., 14, 835427. doi.org/10.3389/fnsyn.2022.835427
* Equal contribution
Jury
- Olivier Thoumine, DR, Université de Bordeaux (Directeur de thèse)
- Jean-Louis Bessereau, PU-PH, Université Claude Bernard Lyon 1 (Rapporteur)
- Fabrice Ango, DR, Université de Montpellier (Rapporteur)
- Aude Panatier, DR, Université de Bordeaux (Examinatrice)
- Sabine Lévi, DR, Université de Bordeaux (Examinatrice)
- Jérôme Ezan, CR, Université de Bordeaux (Examinateur)
- Magali Mondin, IR, Université de Bordeaux (Invitée)