AAV-mediated CSNK2B gene replacement rescues ASD-relevant phenotypes and establishes EEG biomarkers for translation in Csnk2b haploinsufficient mice

De novo CSNK2B variants are strongly associated with autism spectrum disorder (ASD) and early-onset epilepsy, yet in vivo therapeutic evidence and translatable biomarkers remain limited. We generated Csnk2b haploinsufficient (Csnk2b+/–) mice that recapitulate core clinical features—ASD-like social and cognitive deficits, heightened anxiety, spontaneous seizures, cortical and hippocampal structural compromise, and reduced PV-interneuron density with impaired cortical inhibition. Neonatal brain-wide AAV-PHP.eB–mediated CSNK2B replacement (hsyn or CAG promoters, retro-orbital P3) restored cortical/hippocampal structure, normalized neuronal numbers, prolonged survival, and ameliorated seizures and ASD-like behaviors with comparable efficacy across promoters. Critically, treatment also corrected quantitative EEG signatures that are directly deployable in human trials: theta and gamma band power were normalized, theta/gamma (and beta/gamma) ratios recovered, and inter-areal coherence and gamma-band effective connectivity were restored, indicating re-established excitation/inhibition balance and large-scale network coordination. These EEG endpoints constitute a compact, noninvasive biomarker panel of target engagement and physiological efficacy that can be harmonized with clinical EEG to support dose finding, early decision-making, and longitudinal monitoring in CSNK2B gene-therapy trials. Together, our data provide preclinical proof-of-concept that early AAV-mediated CSNK2B replacement is therapeutically effective and nominate band-limited EEG metrics as translational readouts to accelerate first-in-human studies for CSNK2B-linked neurodevelopmental disorders.