NEIL3 shapes hippocampal network dynamics and fear memory through modulation of PV⁺ interneurons

The dynamic balance between excitatory and inhibitory (E/I) signaling is critical for hippocampal network function and memory processing. Here, we uncover a novel role for the DNA glycosylase Endonuclease VIII-like 3 (NEIL3) in maintaining this E/I balance through its impact on parvalbumin-positive (PV⁺) GABAergic interneurons. NEIL3 deficiency leads to a selective reduction in PV⁺ interneurons and impaired perineuronal net (PNN) integrity, likely contributing to further PV⁺ neuron dysfunction. These changes result in altered hippocampal oscillatory dynamics, including increased beta and low gamma power, and reduced high gamma and ripple activity. These network alterations are accompanied by distinct effects on fear memory, as demonstrated using contextual and trace fear conditioning paradigms. NEIL3-deficient mice exhibited enhanced extinction of contextual fear memory but impaired extinction of trace fear memory. These findings suggest that the integrity of inhibitory networks plays differential roles in the spatial versus temporal aspects of fear memory extinction. Transcriptomic analysis further reveals dysregulation of genes involved in glutamatergic and GABAergic signaling. Among these, Gabra2 showed a marked downregulation, potentially driven by changes in promoter DNA methylation. This work identifies NEIL3 as an important regulator of the hippocampal inhibitory network, linking PV⁺ interneuron integrity and oscillatory coordination to distinct memory outcomes, and offers potential mechanistic insight into processes that may contribute to cognitive deficits in disorders characterized by E/I imbalance.