GSE17972
The DNA methylome of human peripheral blood mononuclear cells
DNA methylation plays a vital role in genome dynamics and, in the human genome, occurs predominantly at cytosine guanine dinucleotide (CpG) sites. The diploid haploid human genome analysed here contains around 2060 million CpG sites (methylome) where DNA methylation can vary, affecting many biological processes in health and disease. Using whole-genome bisulfite sequencing, we report the essentially complete (92.6282%) methylome of human peripheral blood mononuclear cells (PBMC) which constitute an important source for clinical blood tests world-wide. We find the majority of CpG sites (68.4% at false positive rate of 0.46%) and only <0.2% of non-CpG sites to be methylated, demonstrating that non-CpG cytosine methylation is negligible in human PBMC.  Analysis of the PBMC methylome revealed a rich landscape of epigenomic data for 20 distinct features including regulatory, protein-coding, RNA gene coding, non-coding and repeat sequences.  Alu element mobility, for instance, was found to negatively correlate with their methylation levels, emphasizing the critical role of DNA methylation in genome stability. Integration of our methylome data with the previously determined genome sequence of the same Asian individual analysed here, enabled a first assessment of allele-specific methylation (ASM) differences between the two haploid methylomes of any individual. Using a conservative cut-off (p <0.001), we identified 599 haploid differentially methylated regions (hDMRs) covering 287 genes. Of these, 76 genes had hDMRs within 2kb of their transcriptional start sites of which >80% displayed allele-specific expression (ASE) after random testing using TA clone sequencing of the same PBMC sample. These data show, that ASM is a recurrent phenomenon and highly correlated with ASE, suggesting that imprinting may be more common than previously thought. Our study not only provides a comprehensive resource for future epigenomic research but also demonstrates a paradigm of large-scale epigenomics studies through new sequencing technology. Overall design: We report the essentially complete (92.6282%) methylome of human peripheral blood mononuclear cells (PBMC) which constitute an important source for clinical blood tests world-wide.