Disrupting Somatic Maintenance of X-Chromosome Inactivation to Reactivate the Inactive X Chromosome

Abstract

X-chromosome inactivation (XCI) in females silences gene expression on one of the two X chromosomes. Following the establishment of XCI early in development, multiple repressive pathways synergistically maintain the silencing of the inactive X (Xi). Females with certain X-linked disorders, such as Rett syndrome and CDKL5 deficiency disorder, may benefit through reactivation of the silenced healthy allele in diseased cells. To identify conditions capable of Xi reactivation, we pursued several approaches that disrupt pathways responsible for maintaining XCI. Here, we screened a small molecule library in an Xi-linked GFP reporter cell line to find druggable targets of XCI maintenance, finding that the Aurora kinase inhibitors VX680 and MLN8237 were capable of reactivating Xi-linked genes. Additionally, we developed antisense oligonucleotides targeting the long noncoding RNA XIST to reactivate disease genes on the Xi in patient cells. Lastly, we explore the use of epigenome editing for targeted, local disruption of Xi silencing.