Knockdown of Ddx3x in mPFC induces autistic-like phenotype in mice via altered synaptic plasticity.

DDX3X, a DEAD-box RNA helicase, has been identified as a risk gene for autism spectrum disorder (ASD). To elucidate the role of DDX3X mutations in ASD pathogenesis, HT22 cell models and mouse models with Ddx3x knockdown specifically in the medial prefrontal cortex were established. Ddx3x knockdown in HT22 cells resulted in slower growth, while in mice, it induced autism-like behaviors. Proteomic analysis in cortex revealed that many down-regulated proteins were involved in synaptic plasticity. The differentially expressed proteins (DEPs) were associated with long-term potentiation, glutamatergic and GABAergic synapses, postsynaptic density, branched-chain amino acid degradation, and the oxytocin pathway. Integrating cellular and cortical omics studies revealed overlaps in the ubiquitin-proteasome system and the 'de novo' protein folding pathway. These pathways were inhibited in the cortex of the model mice. The expression of several important proteins was validated. Confocal microscopy and transmission electron microscopy demonstrated a significant reduction in dendritic spine density and postsynaptic density of mouse models. Electrophysiological experiments showed that the frequency of miniature excitatory postsynaptic currents was significantly reduced. These results suggest that DDX3X deficiency impairs synaptic function, thereby affecting neurodevelopment and social abilities. Abnormal synaptic plasticity may contribute to the pathogenesis of ASD with DDX3X gene mutations.