Comparative DNA methylation profiling of human monocyte-derived macrophages and dendritic cells

In mammals, the dynamics of DNA methylation, in particular the regulated, active removal of cytosine methylation has remained a mystery, partly due to the lack of appropriate model systems to study DNA demethylation. Previous work largely focused on proliferating cell types that had been mitotically arrested using pharmacological inhibitors to distinguish between active and passive mechanisms of DNA demethylation. Here, we characterised this epigenetic phenomenon in a natural setting of post-mitotic cells: the differentiation of human peripheral blood monocytes into macrophages or dendritic cells which proceeds without cell division. We identified many novel examples of active DNA demethylation using a global, comparative CpG methylation profiling approach and characterised accompanying transcriptional and epigenetic events at these sites during monocytic differentiation. Keywords: MCIp-on-Chip; comparative genomic hybridization DNA from monocytes and dendritic cells was separated into methylated and unmethylated pools. Corresponding pools of each cell type were co-hybridized on custom promoter arrays. Methylated and unmethylated pools serve as diametrically oposed technical replicates (mirror image approach). Two biological replicates .