Bhasin et al. provided additional support for this hypothesis by mapping sex-specific expression qtl (eQTL) in mice35. They identified SNPs in putative cis regulatory elements that were associated with variation in gene expression within individuals from one sex, but not the other, indicating that some loci have a regulatory role in males but not in females, or in females but not in males. Because the SNPs are shared among the sexes, differences in the use of cis regulatory elements between the sexes indicate sex-specific differences in trans elements (e.g., transcription factors and co-factors). Sex steroid receptors may be one example of sex-specific trans regulatory elements 36. Similar analyses of human eQTL data have not been performed to date, yet the findings of Bhasin et al.35 are consistent with a growing number of observations23,25,28,30,32 suggesting that ignoring sex in studies of gene expression will underestimate, perhaps quite dramatically, the affect of genetic variations on gene regulation and mRNA abundance.
