Rescuing Neurodevelopmental Deficits in AMPA Receptor Gain-of-Function Mutant

AMPA receptors (AMPARs) mediate fast excitatory synaptic transmission and are essential for neuronal development and brain function. We investigated the role of a recurrent variant in the AMPAR GluA1 subunit <i>(GRIA1</i> p.A636T) identified in individuals with autism spectrum disorder (ASD) and intellectual disability (ID). To test causality and mechanism, we generated a <i>Gria1</i>-A636T knock-in mouse model. Mutant mice exhibited core ASD/ID-like behaviors and a selective hippocampal vulnerability characterized by progressive dendritic atrophy and neuronal loss. Despite reduced GluA1-containing complexes, AMPARs displayed synaptic hyperexcitability and failed to undergo the normal postnatal transition to calcium-impermeable AMPARs, resulting in persistent excitotoxicity. To explore therapeutic intervention, we designed an allele-specific antisense oligonucleotide to specifically silence the mutant transcript. A single neonatal administration of the antisense oligonucleotide entirely prevented hippocampal pathology and ameliorated behavioral deficits. These findings establish <i>GRIA1</i>-A636T as a gain-of-function mutation that drives developmental excitotoxicity and highlight the potential of RNA-targeted precision medicine for neurodevelopmental disorders.