D-repeat in the <i>XIST</i> gene is required for X chromosome inactivation

<i>XIST</i> is a long non-coding RNA, which expressed exclusively from the inactive X chromosome. Although it has been revealed that the A-repeat contributes to the X chromosome inactivation (X-inactivation), the role of the longest D-repeat has not yet been investigated. Here, a sgRNA directed CRISPR/Cas9 system which have multiple target sites within repeat D of <i>XIST</i>, were used to generate D-repeat deletion and studied its roles on X-inactivation. The results showed that the deletion of D-repeat caused a significantly decreased expression of <i>XIST</i>, and up regulated expression of X-linked genes, suggesting that the D-repeat may play an important role in the regulation of <i>XIST</i> expression and silencing of the X-linked genes, which could provide a new idea in the molecular mechanisms of X-inactivation.