that X chromosome to become imprinted and inactivated. Some cells develop into pluripotent cells (the inner cell mass) when the blastocyte forms. There, the imprint is removed, leading to the downregulation of Xist and thus reactivation of the inactive X chromosome. Recent data suggests that Xist activity is regulated by an anti-sense transcript. The epiblast cells are then formed and they begin to be differentiated, and the Xist is upregulated from either of the two X chromosomes and at random in ICM, but the Xist is maintained in epiblast, an X is inactivated and the Xist allele is turned off in the active X chromosome. In maturing XX primordial germ cells, Xist is downregulated and X reactivation occurs once again. Disease linkage Mutations in the XIST promoter cause familial skewed X-inactivation. Interactions XIST has been shown to interact with BRCA1. See also X-inactivation Dosage compensation Tsix References Further reading External links NCBI Xist entry lncRNAdb Xist entry Non-coding RNA