Procognitive restoration of PV neuron plasticity in neurodevelopmental disorders

The hippocampus forms memories of our experiences in populations of coactive pyramidal neurons (PNs)^1-3. Fast-spiking parvalbumin-expressing inhibitory neurons (PV INs) in the dentate gyrus-CA3/CA2 circuit of the hippocampus precisely control PN activity through mossy fibre-dependent feedforward inhibition^4-11. PV INs coordinate experience-dependent changes in their intrinsic excitability, synaptic connectivity, physiology and plasticity properties^9,12-15-referred to here as experience-dependent PV IN plasticity-to regulate PN activity. PV IN impairments in early life, when neural circuitry is highly sensitive to experience, are thought to result in network hyperexcitability, seizures and impaired cognition, which are hallmarks of neurodevelopmental disorders (NDDs)^16-18. Here we designed an input-specific translatome screen to identify regulators of experience-dependent PV IN plasticity genes (XPGs) in the CA3/CA2 subregion of adult hippocampus. We demonstrate that a substantial proportion of upregulated candidate XPGs exhibit haploinsufficiency in autism spectrum disorder, epilepsies, bipolar disorder and schizophrenia, which suggests that there is impaired experience-dependent PV IN plasticity in NDDs. In proof-of-concept experiments, targeted upregulation of a candidate XPG, the homeobox gene Meis2 (ref. ¹⁹), in CA3/CA2 PV INs in an NDD risk mouse model in adulthood is sufficient to restore experience-dependent PV IN plasticity. Moreover, ensemble and sharp-wave ripple properties and cognition were improved, and seizures were suppressed. Thus, experience-dependent PV IN plasticity is a convergent mechanism for NDD risk genes that can be re-instated in adulthood to reverse developmental deficits in circuitry, network excitability and cognition.