Figure 2.

Molecular mechanisms underlying roles of XIST in diseases. (A) X chromosome inactivation (XCI) escape. In female mammals, some X-linked genes can escape from XCI when XIST expression or localization is altered and therefore have biallelic expression, leading to female-biased gene expression, which might contribute to sex-biased diseases. (B) XCI skewness. In female mammals, the paternal and maternal X chromosomes generally have a similar opportunity to be silenced in somatic cells. Under specific condition, however, skewed XCI may occur, which may cause disease in females. (C) MiRNA sponge. The long noncoding transcript XIST can bind various miRNAs, resulting in derepression of miRNA targeted genes and pathology. (D) Regulation in protein activity. XIST can bind to developmentally critical proteins and affect their activity.