Single-cell profiling of DNA methylation in autism spectrum disorder prefrontal cortex reveals distinct regulatory and aging signatures

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition. Studies of postmortem ASD brain tissue have revealed convergent molecular changes across the cortex. Whether these features are reflected in cell-type-specific epigenetic signatures is unknown. Here, we present a single-cell analysis of DNA methylation (DNAm) coupled with transcriptomics in ASD. Using snmCT-seq, we profiled DNAm and transcript levels from over 60,000 nuclei derived from the prefrontal cortex of 49 donors. We identified over 30,000 differentially methylated regions (DMRs) in ASD that were enriched in promoters and cell-type-specific regulatory elements active across the lifespan. ASD-related methylation changes were uncorrelated with transcript levels and were small in magnitude compared with age-associated effects. Age-DMRs were concentrated in excitatory neurons and revealed distinct roles for CG and non-CG methylation. Age-varying methylation signatures of ASD identified neuron projection development as a key process perturbed in ASD, highlighting the heterogeneous impact of ASD across the lifespan.