The pluripotency factor Oct4 interacts with Ctcf and also controls X-chromosome pairing and counting.

During both stem cell differentiation and X-chromosome inactivation (XCI) of mouse embryonic stem cells, chromatin undergoes epigenetic reprogramming. XCI and cell differentiation are tightly coupled, with the blocking of one process compromising the other. The pluripotency factor, Oct4, is now shown to regulate XCI, and is the first identified factor that links both processes.