Monocyte to macrophage differentiation involves major biochemical and structural changes in non-dividing cells. In order to elucidate the role of gene regulatory changes during this process, we used high-throughput sequencing to analyze the complete transcriptome and epigenome of human monocytes that were isolated by elutriation and differentiated in vitro by addition of MCSF in serum-free medium. We also investigated the effect of loading the macrophages with modified LDL. We found that many mRNAs and miRNAs were significantly up- or downregulated during differentiation. While there was no correlation between gene expression and DNA methylation changes at transcription start sites, we identified a large number of intra- and intergenic regions that rapidly lost DNA methylation, became nucleosome-free and gained histone marks indicative of active enhancers. Loading of macrophages with modified LDL caused gene expression changes, but no chromatin changes. In summary, our results demonstrate that monocyte to macrophage differentiation is associated with rapid, highly targeted ... (Show More)

Monocyte to macrophage differentiation involves major biochemical and structural changes in non-dividing cells. In order to elucidate the role of gene regulatory changes during this process, we used high-throughput sequencing to analyze the complete transcriptome and epigenome of human monocytes that were isolated by elutriation and differentiated in vitro by addition of MCSF in serum-free medium. We also investigated the effect of loading the macrophages with modified LDL. We found that many mRNAs and miRNAs were significantly up- or downregulated during differentiation. While there was no correlation between gene expression and DNA methylation changes at transcription start sites, we identified a large number of intra- and intergenic regions that rapidly lost DNA methylation, became nucleosome-free and gained histone marks indicative of active enhancers. Loading of macrophages with modified LDL caused gene expression changes, but no chromatin changes. In summary, our results demonstrate that monocyte to macrophage differentiation is associated with rapid, highly targeted epigenetic changes, whereas lipid uptake mainly affects regulatory circuits of soluble factors.

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