Expression levels of each gene on autosomes and on chromosome X between the two sexes. The FPKM values were logarithmically transformed. The filled dots represent the genes on the X chromosome, whereas the opened dots represent the genes on autosomes. Only genes with detectable expression levels (FPKMs > 0.05) are shown. We found that the higher female mappable fragments of X-linked genes were due to five X-linked Obp genes expressed significantly higher in the female OE (grouped in the red color oval-shaped circle). Highly female-biased genes also included autosomal lipocalin protein genes (Lcn11, Lcn13, and Lcn14) and Mup4. The arrow indicates a highly expressed female-biased pseudogene (ENSMUSG00000082635) located in the X-linked Obp gene cluster.