Florian Donneger

All Publications

• Targeting pathological cells with senolytic drugs reduces seizures in neurodevelopmental mTOR-related epilepsy NATURE NEUROSCIENCE Ribierre, T., Bacq, A., Donneger, F., Doladilhe, M., Maletic, M., Roussel, D., Le Roux, I., Chassoux, F., Devaux, B., Adle-Biassette, H., Ferrand-Sorbets, S., Dorfmueller, G., Chipaux, M., Baldassari, S., Poncer, J., Baulac, S. 2024

  Abstract

  Cortical malformations such as focal cortical dysplasia type II (FCDII) are associated with pediatric drug-resistant epilepsy that necessitates neurosurgery. FCDII results from somatic mosaicism due to post-zygotic mutations in genes of the PI3K-AKT-mTOR pathway, which produce a subset of dysmorphic cells clustered within healthy brain tissue. Here we show a correlation between epileptiform activity in acute cortical slices obtained from human surgical FCDII brain tissues and the density of dysmorphic neurons. We uncovered multiple signatures of cellular senescence in these pathological cells, including p53/p16 expression, SASP expression and senescence-associated β-galactosidase activity. We also show that administration of senolytic drugs (dasatinib/quercetin) decreases the load of senescent cells and reduces seizure frequency in an MtorS2215F FCDII preclinical mouse model, providing proof of concept that senotherapy may be a useful approach to control seizures. These findings pave the way for therapeutic strategies selectively targeting mutated senescent cells in FCDII brain tissue.

  View details for DOI 10.1038/s41593-024-01634-2

  View details for Web of Science ID 001218787300001

  View details for PubMedID 38710875

  View details for PubMedCentralID 5752134

• Hippocampal and neocortical <i>BRAF</i> mutant non-expansive lesions in focal epilepsies NEUROPATHOLOGY AND APPLIED NEUROBIOLOGY Lerond, J., Mathon, B., Scopin, M., Nichelli, L., Guegan, J., Bertholle, C., Izac, B., Andrieu, M., Gareau, T., Donneger, F., Mohand Oumoussa, B., Letourneur, F., Tran, S., Bertrand, M., Le Roux, I., Touat, M., Dupont, S., Poncer, J., Navarro, V., Bielle, F. 2023; 49 (5)

  View details for DOI 10.1111/nan.12937

  View details for Web of Science ID 001091976700001

• Epilepsy related to focal neuronal lipofuscinosis: extra-frontal localization, EEG signatures and GABA involvement JOURNAL OF NEUROLOGY Frazzini, V., Mathon, B., Donneger, F., Cousyn, L., Hanin, A., Nguyen-Michel, V., Adam, C., Lambrecq, V., Dupont, S., Poncer, J., Bielle, F., Navarro, V. 2022; 269 (8): 4102-4109

  Abstract

  Focal neuronal lipofuscinosis (FNL) is an uncommon epileptic disorder related to an excess of lipofuscin accumulation within dysmorphic-appearing neurons (DANs), whose epileptogenic mechanisms are still poorly understood. It shares some clinical and neuroimaging similarities with focal cortical dysplasia of type IIb (FCDIIb), but it represents a different pathological entity. Here, we identified two patients with FNL among a 10-year cohort of 323 patients who underwent neurosurgery for a focal pharmacoresistant epilepsy. We describe the electroclinical, metabolic and neuropathological features of both patients with FNL who benefited from a comprehensive presurgical investigation. While the previous reports showed frontal lobe localization of the lesion, FNL was identified in the temporal lobe, in one of our patients. EEG investigations in both patients showed striking focal and rich interictal activity resembling that described in FCDIIb. Besides focal intraneuronal lipofuscin accumulation, the neuropathological analysis demonstrated that somata of DANs were surrounded by a large amount of GABAergic presynaptic buttons, suggesting the involvement of interneurons in the epileptogenicity of FNL. To further explore the role of GABAergic transmission in the generation of epileptiform activity in FNL, we performed in vitro multi-electrode array recordings on the post-surgery tissue from one patient. Spontaneous interictal-like discharges (IILDs) were identified only in the restricted area displaying the highest density of lipofuscin-containing DANs, suggesting a close correlation between the density of lipofuscin-containing neurons and epileptogenicity. Moreover, IILDs were blocked by the GABAA receptor antagonist gabazine. All together, these findings showed how GABA signaling may contribute to the generation of interictal-like activity in FNL tissue.

  View details for DOI 10.1007/s00415-022-11024-y

  View details for Web of Science ID 000765734500002

  View details for PubMedID 35254479

• Gephyrin Interacts with the K-Cl Cotransporter KCC2 to Regulate Its Surface Expression and Function in Cortical Neurons JOURNAL OF NEUROSCIENCE Al Awabdh, S., Donneger, F., Goutierre, M., Seveno, M., Vigy, O., Weinzettl, P., Russeau, M., Moutkine, I., Levi, S., Marin, P., Poncer, J. 2022; 42 (2): 166-182

  Abstract

  The K+-Cl- cotransporter KCC2, encoded by the Slc12a5 gene, is a neuron-specific chloride extruder that tunes the strength and polarity of GABAA receptor-mediated transmission. In addition to its canonical ion transport function, KCC2 also regulates spinogenesis and excitatory synaptic function through interaction with a variety of molecular partners. KCC2 is enriched in the vicinity of both glutamatergic and GABAergic synapses, the activity of which in turn regulates its membrane stability and function. KCC2 interaction with the submembrane actin cytoskeleton via 4.1N is known to control its anchoring near glutamatergic synapses on dendritic spines. However, the molecular determinants of KCC2 clustering near GABAergic synapses remain unknown. Here, we used proteomics to identify novel KCC2 interacting proteins in the adult rat neocortex. We identified both known and novel candidate KCC2 partners, including some involved in neuronal development and synaptic transmission. These include gephyrin, the main scaffolding molecule at GABAergic synapses. Gephyrin interaction with endogenous KCC2 was confirmed by immunoprecipitation from rat neocortical extracts. We showed that gephyrin stabilizes plasmalemmal KCC2 and promotes its clustering in hippocampal neurons, mostly but not exclusively near GABAergic synapses, thereby controlling KCC2-mediated chloride extrusion. This study identifies gephyrin as a novel KCC2 anchoring molecule that regulates its membrane expression and function in cortical neurons.SIGNIFICANCE STATEMENT Fast synaptic inhibition in the brain is mediated by chloride-permeable GABAA receptors (GABAARs) and therefore relies on transmembrane chloride gradients. In neurons, these gradients are primarily maintained by the K/Cl cotransporter KCC2. Therefore, understanding the mechanisms controlling KCC2 expression and function is crucial to understand its physiological regulation and rescue its function in the pathology. KCC2 function depends on its membrane expression and clustering, but the underlying mechanisms remain unknown. We describe the interaction between KCC2 and gephyrin, the main scaffolding protein at inhibitory synapses. We show that gephyrin controls plasmalemmal KCC2 clustering and that loss of gephyrin compromises KCC2 function. Our data suggest functional units comprising GABAARs, gephyrin, and KCC2 act to regulate synaptic GABA signaling.

  View details for DOI 10.1523/JNEUROSCI.2926-20.2021

  View details for Web of Science ID 000744037500002

  View details for PubMedID 34810232

  View details for PubMedCentralID PMC8802937

• Cation-chloride cotransporters and the polarity of GABA signalling in mouse hippocampal parvalbumin interneurons JOURNAL OF PHYSIOLOGY-LONDON Otsu, Y., Donneger, F., Schwartz, E. J., Poncer, J. 2020; 598 (10): 1865-1880

  Abstract

  Cation-chloride cotransporters (CCCs) play a critical role in controlling the efficacy and polarity of GABAA receptor (GABAA R)-mediated transmission in the brain, yet their expression and function in GABAergic interneurons has been overlooked. We compared the polarity of GABA signalling and the function of CCCs in mouse hippocampal pyramidal neurons and parvalbumin-expressing interneurons. Under resting conditions, GABAA R activation was mostly depolarizing and yet inhibitory in both cell types. KCC2 blockade further depolarized the reversal potential of GABAA R-mediated currents often above action potential threshold. However, during repetitive GABAA R activation, the postsynaptic response declined independently of the ion flux direction or KCC2 function, suggesting intracellular chloride build-up is not responsible for this form of plasticity. Our data demonstrate similar mechanisms of chloride regulation in mouse hippocampal pyramidal neurons and parvalbumin interneurons.Transmembrane chloride gradients govern the efficacy and polarity of GABA signalling in neurons and are usually maintained by the activity of cation-chloride cotransporters, such as KCC2 and NKCC1. Whereas their role is well established in cortical principal neurons, it remains poorly documented in GABAergic interneurons. We used complementary electrophysiological approaches to compare the effects of GABAA receptor (GABAA R) activation in adult mouse hippocampal parvalbumin interneurons (PV-INs) and pyramidal cells (PCs). Loose cell-attached, tight-seal and gramicidin-perforated patch recordings all show GABAA R-mediated transmission is slightly depolarizing and yet inhibitory in both PV-INs and PCs. Focal GABA uncaging in whole-cell recordings reveal that KCC2 and NKCC1 are functional in both PV-INs and PCs but differentially contribute to transmembrane chloride gradients in their soma and dendrites. Blocking KCC2 function depolarizes the reversal potential of GABAA R-mediated currents in PV-INs and PCs, often beyond firing threshold, showing KCC2 is essential to maintain the inhibitory effect of GABAA Rs. Finally, we show that repetitive 10 Hz activation of GABAA Rs in both PV-INs and PCs leads to a progressive decline of the postsynaptic response independently of the ion flux direction or KCC2 function. This suggests intraneuronal chloride build-up may not predominantly contribute to activity-dependent plasticity of GABAergic synapses in this frequency range. Altogether our data demonstrate similar mechanisms of chloride regulation in mouse hippocampal PV-INs and PCs and suggest KCC2 downregulation in the pathology may affect the valence of GABA signalling in both cell types.

  View details for DOI 10.1113/JP279221

  View details for Web of Science ID 000513720800001

  View details for PubMedID 32012273

• KCC2 Regulates Neuronal Excitability and Hippocampal Activity via Interaction with Task-3 Channels CELL REPORTS Goutierre, M., Al Awabdh, S., Donneger, F., Francois, E., Gomez-Dominguez, D., Irinopoulou, T., Menendez de la Prida, L., Poncer, J. 2019; 28 (1): 91-+

  Abstract

  KCC2 regulates neuronal transmembrane chloride gradients and thereby controls GABA signaling in the brain. KCC2 downregulation is observed in numerous neurological and psychiatric disorders. Paradoxical, excitatory GABA signaling is usually assumed to contribute to abnormal network activity underlying the pathology. We tested this hypothesis and explored the functional impact of chronic KCC2 downregulation in the rat dentate gyrus. Although the reversal potential of GABAA receptor currents is depolarized in KCC2 knockdown neurons, this shift is compensated by depolarization of the resting membrane potential. This reflects downregulation of leak potassium currents. We show KCC2 interacts with Task-3 (KCNK9) channels and is required for their membrane expression. Increased neuronal excitability upon KCC2 suppression altered dentate gyrus rhythmogenesis, which could be normalized by chemogenetic hyperpolarization. Our data reveal KCC2 downregulation engages complex synaptic and cellular alterations beyond GABA signaling that perturb network activity thus offering additional targets for therapeutic intervention.

  View details for DOI 10.1016/j.celrep.2019.06.001

  View details for Web of Science ID 000473423800009

  View details for PubMedID 31269453