Multilevel investigation of the Shank3 mouse model of ASD reveals novel insight into disease mechanisms and therapeutic perspectives

Autism Spectrum Disorder (ASD) is a heterogeneous neurodevelopmental condition characterized by impairments in social communication, restricted interests, repetitive behaviors, and sensory processing abnormalities. Among the strongest genetic risk factors for ASD are mutations in the SHANK3 gene, which encodes a postsynaptic scaffolding protein essential for the development and maintenance of excitatory synapses. SHANK3 deficiency disrupts synaptic organization and neural circuit function, contributing to the cognitive and behavioral features observed in affected individuals. This thesis aimed to investigate the behavioral and functional consequences of SHANK3 deficiency, with a particular focus on somatosensory processing alterations, and to evaluate whether a single administration of Compound K could ameliorate these deficits. A secondary objective was to characterize the behavioral and electrophysiological phenotype of Shank3 heterozygous mice, which more closely model the partial SHANK3 deficiency observed in patients. Using the ShankΔ13–16 (Shank3B) mouse model, a multimodal approach combining behavioral testing, in vivo wide-field calcium imaging, and ex vivo whole-cell patch-clamp recordings was employed. Sensory processing was assessed through the texture Novel Object Recognition Test (tNORT) and functional imaging of the primary somatosensory barrel cortex (SSp-Bfd). Electrophysiological recordings from layer V pyramidal neurons were performed to examine intrinsic membrane properties and excitatory synaptic transmission. In parallel, Shank3B heterozygous mice underwent behavioral assays evaluating locomotion, repetitive behaviors, and social interaction, followed by electrophysiological recordings from ventral CA1 hippocampal pyramidal neurons. Shank3B knockout mice exhibited impaired tactile discrimination and reduced sensory-evoked cortical responses, indicating disrupted somatosensory processing. At the cellular level, enhanced excitatory synaptic transmission and sex-dependent alterations in neuronal excitability were observed. Compound K did not restore large-scale cortical activity or synaptic transmission but selectively normalized intrinsic excitability in female knockout neurons, suggesting a partial and sex-specific effect. Heterozygous mice displayed milder yet consistent behavioral abnormalities, including increased repetitive behaviors and impaired long-term social memory, alongside early synaptic dysfunction in the ventral CA1 region. Specifically, reduced frequency of spontaneous excitatory postsynaptic currents suggested presynaptic alterations without major postsynaptic changes. Overall, these findings demonstrate that SHANK3 deficiency leads to multi-level disruptions in cortical and hippocampal circuits, with significant sex-dependent features. By integrating behavioral, cellular, and network-level analyses, this work provides insight into early functional alterations associated with ASD and contributes to the evaluation of potential translational therapeutic strategies.