KDM6A facilitates Xist upregulation at the onset of X inactivation.

X chromosome inactivation (XCI) is a female-specific process in which one X chromosome is silenced to balance X-linked gene expression between the sexes. XCI is initiated in early development by upregulation of the lncRNA on the future inactive X (Xi). A subset of X-linked genes escape silencing and thus have higher expression in females, suggesting female-specific functions. One of these genes is the highly conserved gene , which encodes a histone demethylase that removes methyl groups at H3K27 to facilitate gene expression. Here, we investigate the role of KDM6A in the regulation of . We observed impaired upregulation of during early stages of differentiation in hybrid mouse ES cells following CRISPR/Cas9 knockout of . This is associated with reduced RNA coating of the Xi, suggesting diminished XCI potency. Indeed, knockout results in aberrant overexpression of genes from the Xi after differentiation. KDM6A binds to the promoter and knockout cells show an increase in H3K27me3 at . These results indicate that KDM6A plays a role in the initiation of XCI through histone demethylase-dependent activation of during early differentiation.