Autism-like behavior induced by conditional ablation of the Bassoon gene in GABAergic interneurons

Synaptic dysfunction and resulting imbalance of excitatory vs. inhibitory transmission are fundamental aspects of autism spectrum disorders (ASD). Here we addressed the role of inhibitory synapse disturbances in ASD employing mice with a conditional ablation in inhibitory forebrain interneurons of the presynaptic active zone scaffolding protein Bassoon (Bsn), a key factor in synaptic development, activity and maintenance. The conditional Bsn gene knock out resulted in a reduction of synaptic vesicles and reduced synaptic efficacy of affected inhibitory synapses as well as diminished GABAergic inhibition in hippocampal pyramidal neurons. Bsn mutants further displayed a reconfiguration of the hippocampal synaptic network in vivo , as seen in subfield-specific changes of inhibitory synaptic markers and reduced numbers of parvalbumin interneurons, culminating in disturbance of hippocampal network activity patterns and profound mitochondrial and metabolic dysregulation. Importantly, the mutant mice developed behavioral abnormalities reminiscent of ASD including widespread social behavioral deficits and novelty-induced hyperarousal with altered motor behavior, increased anxiety and epileptiform activity. Bsn conditional knock out mice thus provide strong evidence for a causal involvement of GABAergic synapses in the emergence of ASD-related behavioral and physiological phenotypes.