Fig. 2.

A, Global sex differences in the mouse transcriptome of tissues not directly involved in reproduction. Histograms show male (M):female (F) ratios of expression of all mRNA measured by microarray profiling in mice (i.e. genes with 2-fold higher expression in males are +1 and those with 2-fold higher in females are −1). Sex differences were found in 72% of liver genes and 68% of adipose. Over 70% of genes showing sex bias have less than 20% greater expression in one sex relative to the other, and sex differences of 2-fold are rare. X-inactivation prevents strong female bias in expression of X genes (red curve), and results in sex bias in X genes that roughly matches, tissue for tissue, the global sex bias of autosomal genes (black curve) with which they interact in each tissue. Republished from Ref. 43 based on data of Ref. 23. B, Sex differences in the human plasma metabolome; 131 metabolites are graphed by the first two principal components (PC) in a partial least square analysis of levels of metabolites in human plasma; 78% of metabolites showed statistically significant sex differences. Reprinted with permission from Ref. 31.