Epigenetic Regulation of Open Chromatin in Pluripotent Stem Cells

The recent progress in pluripotent stem cell research has opened new avenues of disease modeling, drug screening, and transplantation of patient-specific tissues. It has long been thought that the chromatin of pluripotent stem cells is globally open to enable the timely activation of essentially all genes in the genome during differentiation into multiple lineages. The current article reviews descriptive observations and the epigenetic machinery relevant to what is supposed to be globally open chromatin in pluripotent stem cells. Detailed analyses of each epigenetic element, however, have revealed that the globally open chromatin hypothesis is not necessarily supported by some of the critical experimental evidence, such as genome-wide nucleosome accessibility and nucleosome positioning. Further understanding of the epigenetic gene regulation is expected to determine the true nature of the so-called globally open chromatin in pluripotent stem.