X-chromosome inactivation (XCI) is a process by which one of the copies of the X chromosome in mammalian female cells is inactivated. The XCI causes a balanced X-linked gene quantity between male and females; moreover, it results mosaic females which have paternal active X in some cells and maternal active X in others. Cellular mosaicism is a noteworthy phenomenon and lowers the risk of X-linked diseases in women because the presentation of a mutation on both X chromosomes is unlikely. Therefore, in heterozygous females, the XCI will be present only on the half of the X genome. In contrast, a similar mutation will present in all of the cells of men.Female carriers of some neurological disorders such as autism, Rett syndrome, adreno-leukodystrophyand X-linked mental retardation are reported to present XCI. These observations underscore the important role of X chromosome in the brain which may be related to the existence of a chromosomal signature of gene expression associated with the X-chromosome for neurological conditions not normally associated with that chromosome.In this review, we focused on latestinvestigations on the role of XCI in neurodevelopmental disorders and how these investigations can be effective in the treatment of neurodevelopmental disorders.
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