||P.2 right column top paragraph: "Here, by rigorous analysis of RNA-sequencing (RNA-seq) data from the GTEx [Genotype-Tissue Expression] project [refs 27, 28], [investigators] have comprehensively mapped, for the first time, human adults sex-differential gene expression over 45 tissues common to both sexes. [They] then identified highly and moderately sex-specific genes while considering the complete panel of 53 tissues."
||P.2 right column bottom paragraph: "On the background of similar expression in most tissues of most genes (Additional file 2: Figure S2, Additional file 3: Table S1), there are over 6500 protein-coding genes with significant SDE [Sex-differentially expression] in at least one tissue. Most of these genes have SDE in just one tissue, but about 650 have SDE in two or more tissues, 31 have SDE in more than five tissues, and 22 have SDE in nine or more tissues (Additional file 4: Figure S3 and Additional file 5: Table S2). As expected, Y-linked genes that are normally carried only by men show SDE in many tissues. Nevertheless, 16 out of the 244 X-linked SDE genes also have widespread SDE (across six or more tissues, Additional file 5: Table S2) in either men or women. [Investigators] found that three of these X-linked genes are located at pseudo-autosomal region 1 (PAR1), which undergoes relatively frequent recombination between the X and Y chromosomes and is known to escape X-inactivation [ref 33] (Additional file 5: Table S2, Additional file 6: Figure S4). It is noteworthy that these PAR1 genes have men-biased expression." P.8 left column bottom paragraph: "Mapping sex-differential gene expression [investigators] found more than 6500 protein-coding genes with significant SDE in one tissue or more. The most differentiated tissue was the breast mammary gland, with more than 6000 genes having significant SDE (Fig. 1). This remarkable sex-biased gene expression is likely due to the distinct physiologic properties of this tissue between men and women [ref 2]. In evolutionary terms, differential selection between the sexes of so many genes that are likely involved in lactation, an essential reproductive trait, might inhibit optimal adaptation of this trait due to its distinct importance in men and women."