More recently, GWGE studies have also been used to identify functional DNA variation in the genome, variation that influences the expression or splicing of genes. The data generated from such studies is expected to be very useful for the study of complex disorders as it will allow the assessment of the functionality of variants identified through GWAS. In a recent review Cookson et al (19) calculated that 10–15% of GWAS signals involved a known regulatory variant, often called an expression quantitative trait locus (eQTL). This number will likely increase as we identify more eQTLs through new gene expression mapping studies. The NIH has recognized the necessity of linking gene regulation to genetic variation and has recently launched the Genotype-Tissue Expression (GTEx) project (http://nihroadmap.nih.gov/GTEx/), a pilot project that will ultimately lead to a gene regulation database involving multiple tissues from 1,000 donors with genome-wide variation information, a much anticipated resource.
