Global survey of escape from X inactivation by RNA-sequencing in mouse

X inactivation equalizes the dosage of gene expression between the sexes, although some genes escape silencing. We performed RNA-sequencing in Mus musculus x Mus spretus cells, relying on expression of SNPs to discriminate allelic origin. We found 15/387 (4%) mouse genes with significant expression from the inactive X, including 10 novel escape genes. We estimate that mice have significantly fewer escape genes compared with humans.