Stabilization of Xist RNA mediates initiation of X chromosome inactivation

Modulation of Xist RNA was studied to identify its effects on the developmental up-regulation of the X transcript. Results show that up-regulation of Xist RNA marks the beginning of X inactivation due to the increased stability of the transcript it has caused. However, an unstable transcript is caused by the inhibition of the Xist allele such as in the XX ES cells and in XX embryos which also occurs at the onset of X inactivation.