Structural and Functional Brain-wide Alterations in A350V IQSEC2 Mutant Mice Displaying Autistic-like Behavior

Abstract

IQSEC2 is an X-linked gene which is associated with autism spectrum disorder (ASD), intellectual disability and epilepsy. IQSEC2 is a postsynaptic density protein, localized on excitatory synapses as part of the NMDA receptor complex and is suggested to play a role in AMPA receptor trafficking and mediation of long-term depression. Here, we present brain-wide structural volumetric and functional connectivity characterization in a novel mouse model with a missense mutation in the IQ domain of IQSEC2 (A350V). Using high-resolution structural and functional MRI, we show that animals with the A350V mutation display increased whole-brain volume which was further found to be specific to the cortex and hippocampus. Moreover, using a data-driven approach we demonstrate that A350V mice present alterations in structure-function relations of the frontal, auditory, and visual networks. Examination of these alterations revealed an increase in functional connectivity between the anterior cingulate cortex and the dorsomedial striatum. We also show that corticostriatal functional connectivity is correlated with individual variability in social behavior only in A350V mice, as assessed using the three-chamber social preference test. Our results at the systems-level bridge the impact of previously reported changes in AMPA receptor trafficking to network-level disruption and impaired social behavior. Further, the A350V mouse model recapitulates similarly reported brain-wide changes in other ASD mouse models, with substantially different cellular-level pathologies that nonetheless result in similar brain-wide alterations, suggesting that novel therapeutic approaches in ASD that result in systems-level rescue will be relevant to IQSEC2 mutations. Significance StatementSeveral recent studies have characterized the changes in the organization of brain networks in animal models of autism spectrum disorders (ASD). Here we assessed the effect of an A350V missense mutation in the IQSEC2 gene, which is associated with ASD, on brain-wide functional connectivity and its relation to social behavior deficits in A350V mice relative to controls. We found that the A350V IQSEC2 model results in disrupted functional connectivity of the anterior cingulate cortex and the dorsomedial striatum. Critically, disrupted increased corticostriatal functional connectivity is predictive of individual variability in social interaction only in A350V mice implicating this pathway in the pathophysiology of the A350V IQSEC2 mutation.