Figure 2

Chromatin states during differentiation of adult stem cells and reprogramming of somatic cells. The figure shows the epigenetic alterations of genes associated with pluripotency, cell maintenance, and lineage specification during stem cell differentiation. CpG methylation is grouped into three types of promoters classified with respect to their CpG content: high CpG promoter (HCP), intermediate CpG promoter (ICP), and low CpG promoter (LCP). Bivalent domains of histone marks (trimethylated histone H3 at lysine 4 and trimethylated histone H3 at lysine 27) are represented. Reprogramming of somatic cells toward pluripotent cells - that is, induced pluripotent cells (iPS) - implies a turnover of the epigenetic landscape of adult differentiated cells, including silencing of tissue-specific genes and activation of pluripotency-related genes.