Highly efficient XIST reactivation in female hPSC by transient dual inhibition of TP53 and DNA methylation during Cas9 mediated genome editing.

The irreversible erosion of X-chromosome inactivation (XCI) due to repression of the long non-coding RNA XIST presents a major challenge for disease modeling and raises safety concerns for the clinical application of female human pluripotent stem cells (hPSCs) due to the aberrant overexpression of X-linked genes. While Cas9-mediated non-homologous end joining (NHEJ) targeting the XIST promoter can induce DNA demethylation and restore XCI by reactivating XIST, its efficiency remains low. Here, we introduce a highly efficient strategy for XIST reactivation by combining TP53 inhibition with suppression of DNA methylation maintenance during Cas9-mediated NHEJ. This dual-inhibition approach increased the proportion of XIST-positive hPSCs from ~ 5 to ~ 43.7%, providing a robust method for stabilizing XCI in female hPSCs for diverse applications.