Moesin deficiency leads to microglia-mediated synaptic pruning and social abnormality: a post-GWAS functional genomics study

Genome-wide association studies (GWAS) implicated a noncoding antisense RNA designated as MSNP1AS in susceptibility to autism spectrum disorders (ASD). MSNP1AS binds to and downregulates the Moesin (MSN) transcript and is highly overexpressed in postmortem cerebral cortex of individuals with ASDs. However, the mechanistic link between Moesin loss in vivo and ASD-related phenotypic traits remains enigmatic. Here, we generated Moesin knockout (Msn KO) mice, on which neurobehavioral tests revealed impaired social novelty and repetitive behaviors. Single-cell transcriptomics and electrophysiology recording indicated activated status of the microglia, leading to aberrant C1q-dependent synaptic pruning followed by synaptic deficits in medial prefrontal cortex in KO mice. Aberrant regulatory pathway from sequencing data guided us to block type I interferon pathway by IFNAR1 blocking antibody via nasal administration, which rescued microglial abnormalities and social deficits in Msn KO mice. Taken together, Moesin mediates interferon signaling and synaptic pruning to affect ASD-like behaviors, providing a functional genetic link between MSN and neurobehavioral abnormalities. Following tissue dissociation and enzymatic digestion, cortical microglia from adult Msn knockout C57BL/6 mice were isolated via Percoll gradient centrifugation and Fluorescence-activated cell sorting (FACS) using CD45 and CD11b antibodies, and subsequently analyzed by single-cell RNA sequencing (scRNA-seq) with alignment to the GRCm39 genome and Seurat-based clustering.