Investigating Sex-Specific Effects of Cortical β3 Integrin on Autism and Epilepsy: A Behavioral Characterization Study

Autism Spectrum Disorder (ASD) is a group of neurodevelopmental disorders characterized by the early onset of social communication impairments, repetitive behaviors, highly restricted interests and/or sensory behaviour anomalies. Epilepsy is a brain disorder, or family of disorders, diagnosed after the occurrence of at least one epileptic seizure (unpredictable interruptions of normal brain function) and characterized by an increased predisposition to the generation of epileptic seizures with neurobiological, cognitive, psychological, and social consequences. There is a high comorbidity rate between ASD and epilepsy, as they share several common risk factors. Both ASD and epilepsy show neurodevelopmental deficits related to inhibitory and excitatory circuits, with dysfunctions in the GABAergic and glutamatergic systems observed in both conditions. Alterations of expression or function of cell adhesion molecules (CAMs), such as integrins, can impair neural network excitability and dysregulate synaptic transmission. Integrins are biomechanical receptors that connect both physically and functionally the extracellular matrix (ECM) to the intracellular cytoskeleton, regulating synaptic connectivity and plasticity in response to extracellular cues. Each integrin heterodimer is composed of an α and a β subunit. In particular, in the brain, β3 integrin interacts with the αV subunit to form the αVβ3 integrin heterodimer, which mediates adhesion strengthening of excitatory synapses in cortical pyramidal neurons. Specifically, β3 integrin haplo-insufficiency impairs network excitability and synchrony of cortical neuronal networks. The Itgb3 KO mouse is a well-established model of ASD. However, due to the male-to-female prevalence ratio in ASD, most studies have focused primarily on males and consequences of ablation of β3 integrin expression in females remain largely unknown. Thus, I decided to behaviorally characterize WT (Itgb3+/+), HET (Itgb3+/-) and KO (Itgb3-/-) female mice focusing on tasks involving sociability (aspects related to ASD), and the measurement of threshold for seizures (propensity for epilepsy). I found that variations in the expression level of β3 integrin affect males and females differently. KO and HET female mice showed an increased susceptibility to seizure but no deficits in social interactions. Since both male and female Itgb3 HET mice exhibited increased seizure susceptibility, I decided to exploit the CRISPRa technology to restore physiological β3 integrin expression and rescue their epileptic phenotype. Therefore, I tested the threshold for seizures induced by PTZ in both female and male CRISPRa-treated mice, demonstrating the effectiveness of this technology in reducing seizure susceptibility. In addition, I used the CRISPRa system to increase the endogenous β3 integrin expression in WT mice. Alteration of physiological levels of β3 integrin led to the manifestation of defects in social novelty preference and habituation to social stimuli, specifically in male mice. This study provides valuable insights into how β3 integrin regulates social behaviour and may enhance our understanding of the downstream synaptic effects resulting from impairments in presynaptic and postsynaptic molecules. Targeting this mechanoreceptor could offer new possibilities for developing therapeutic strategies for ASD and related forms of epilepsy.