NEUROANATOMICAL CHARACTERIZATION OF NEUROLIGIN-2-MEDIATED GEPHYRIN AGGREGATION

Impairment of inhibitory neuronal activity is linked to behavioral abnormalities in psychiatric disorders, thereby emphasizing that understanding inhibitory synaptic transmission is crucial for the development of new therapeutic strategies. Inhibition in the central nervous system is primarily mediated by GABAergic neurotransmission. Core components of GABAergic synapses include GABA_A receptors, which are anchored at the postsynaptic membrane by a complex containing the scaffolding protein gephyrin and the cell adhesion protein neuroligin-2 (Nlgn2). Notably, variants in Nlgn2 are associated with a spectrum of psychiatric phenotypes including anxiety and schizophrenia, and Nlgn2 knockout (KO) mice cause prominent anxiety behavior. Additionally, previous research from our group demonstrated that the anxiety phenotype in Nlgn2 KO mice is accompanied by the development of significant gephyrin aggregation, raising the intriguing question of whether gephyrin aggregation might contribute to the pathophysiology of Nlgn2 variants. In the present study, neuroanatomical characterization of gephyrin aggregates in Nlgn2 KO mice revealed that aggregates are localized in specific layers of key brain regions, including hippocampus, cortex, thalamus and amygdala. In addition, the aggregates were found to colocalize with Ankyrin G, indicating their presence in the axon initial segment rather than at somatodendritic compartment or synaptic sites. Importantly, Nlgn2 deletion impaired the activity-dependent modulation of gephyrin aggregation observed in WT neuronal cultures, uncovering a mechanism that may conceivably contribute to the behavioral abnormalities observed in Nlgn2 KO mice. Together, our results reveal key insights into the molecular mechanisms underlying Nlgn2-mediated gephyrin aggregation and provide the rationale for investigating therapeutic strategies targeting gephyrin aggregates.