Autism spectrum disorder (ASD) is a neurodevelopmental condition with a 4:1 male bias, yet the biological basis for this sex difference remains poorly understood. Heterozygous mutations in the chromatin remodeler CHD8 confer high risk for ASD, with phenotypes influenced by sex and genetic background. Here, we generated Chd8 +/R2219* mice carrying a CRISPR-Cas9-generated mutation orthologous to a human variant. These mice recap...