Open Chromatin, Epigenetic Plasticity, and Nuclear Organization in Pluripotency

Pluripotent embryonic stem cells (ESCs) are considered to have open and accessible chromatin relative to differentiated cells. However, as many studies supporting these conclusions relied on ESCs grown in serum, it has been suggested that some of these features are the result of culture conditions, particularly as more recent work using GSK3/MEK inhibitors ("2i") to mimic "ground-state" conditions of the pre-implantation blastocyst observed some altered epigenetic features. Here, we systematically review chromatin and epigenetic features in 2i- and serum-grown conditions to come to a clearer picture of what are genuine characteristics of pluripotency and what open chromatin features predict pluripotency.