Xist2lox/2lox floxed mice have loxP sites flanking exons 1-3, as well as 5 kb of the proximal promoter, of the X-linked inactive X specific transcripts (Xist) gene. XIST is a non-coding gene identified within the X inactivation center (XIC) of the inactive X chromosome, and is essential for the initiation and spread of X-inactivation. The expression of XIST spreads in cis along the entire chromosome and recruits additional silencing factors, which together establish stable repression of that chromosome for the lifetime of the cell and its progeny. This repression continues during the maintenance phase, generating a cloud of XIST that surrounds the inactive X chromosome. Females that are homozygous and males that are hemizygous for this allele are viable and fertile. When bred to mice that express tissue-specific Cre recombinase, exons 1-3, as well as 5 kb of the proximal promoter, will be removed in the cre-expressing tissues of the offspring.

Xist2lox/2lox floxed mice have loxP sites flanking exons 1-3, as well as 5 kb of the proximal promoter, of the X-linked Xist gene. These mice may be useful when studying X chromosome inactivation and reactivation.