Sex-biased methylome and transcriptome in human prefrontal cortex

Brain function and cognitive performance differ between men and women in some measures. The phenotypic variation may be partially due to sex differences in epigenomes and transcriptomes in specific brain regions [e. g. the prefrontal cortex (PFC)]. Genome-wide DNA methylation and gene expression were examined in postmortem PFC of 32 males and 14 females (all were Caucasians) using Illumina's 450K Methylation and HT-12 v4 Gene Expression BeadChips, respectively. Multiple linear regression, Pearson correlation and DAVID functional annotation analyses were applied to investigate sex-biased DNA methylation and gene expression, DNA methylation-gene expression correlation and gene ontology (GO) annotations overrepresented by differentially methylated and expressed genes. A total of 22 124 CpGs showed differential methylation between males and females (2.6 x 10(-38) <= P-nominal <= 0.05), and the P-values of 8357 CpGs withstood multiple-testing correction (q < 0.05). A total of 1489 genes showed differential expression between males and females (4.1 x 10(-36) <= P-nominal <= 0.05), and the P-values of 35 genes survived multiple-testing correction (q < 0.05). A significant correlation (P-correlation < 0.05) was observed between methylation levels of 585 differentially methylated CpGs (P-nominal <= 0.05) and expression levels of 188 differentially expressed host genes (P-nominal < 0.05). The GO terms enriched by these 188 genes (134 on autosomes and 54 on sex chromosomes) were assigned to 24 clusters, and 33 genes involved in the top cluster (enrichment score: 4.7) mainly participate in ribosome structure and function, RNA binding and protein translation. This study demonstrated sex-specific methylomic and transcriptomic profiles in the human PFC. Our findings suggest that sex-biased DNA methylation and gene expression could be either the cause or consequence of differential brain development between males and females.