Review Volume 4, Issue 12 pp 878—886

Figure 1. A schematic representation of ESCs biology. (A) The stemness of ESCs is maintained by intrinsic (i.e. SOX2, NANOG and OCT4) and by extrinsic pathways (i.e. LIF, BMP4 and FGF). MicroRNAs also play a role in the maintenance of stem cells, and some are expressed during self-renewal (miR-269, miR-290-295 cluster, miR-371, miR-200c) while others are up-regulated during differentiation (miR-21, miR-22, miR-29, miR-134, miR-296, miR-470) (see text for details). (B) Role of p53 in the maintenance of genomic stability in ESCs. During DNA damage, p53 is activated (via Ser315 phosphorylation) and binds the Nanog promoter to repress its expression. The outcome of p53 activation is to induce the differentiation of ESCs into other cell types that they can go into a senescent state or induces apoptosis to preserve genome stability.