Cell type and species-specific methylation patterns in neuronal and non-neuronal cells of human and chimpanzee cortex

Using reduced representation bisulfite sequencing (RRBS), we have compared the methylomes of neuronal and non-neuronal cells from three female human and three chimpanzee cortices (Brodmann area 10). Differentially methylated regions (DMRs) with genome-wide significance were enriched in specific chromosomal regions. Intraspecific methylation differences between neuronal and non-neuronal cells were approximately three times more abundant than interspecific methylation differences between human and chimpanzee cell types. The vast majority (>90%) of human intraspecific DMRs (including DMRs with retrotransposons) were hypomethylated in neurons, compared to glia. Intraspecific DMRs were enriched in genes that have been associated with different neuropsychiatric disorders. Interspecific DMRs were enriched in genes showing human-specific brain histone modifications. Methylation differences between human and chimpanzee non-neuronal cells (N=666) were much more frequent than neuronal interspecific DMRs (N=96). More than 95% of interspecific non-neuronal DMRs were hypermethylated in humans. Comparison of methylation of 3 human neuronal cell, 3 human non-neuronal, 3 chimpanzee neuronal cell and 3 chimpanzee non-neuronal cell RRBS libraries