Because of their easier interpretation, genetic variants in the coding sequence of a gene and present in the expressed coding regions (exons) have often been given priority, although it has long been clear that coding sequence variants per se were insufficient for mapping complex diseases.9 However, variants in the intervening sequences (introns) or in the untranslated regions (UTRs), although not changing the predicted protein sequence, may be pivotal in the regulation of gene expression. The UTRs are the mRNA sequences flanking the beginning and end of the coding sequence; as their name suggests, UTRs are part of the mRNA but are not translated into protein. Notably, 3.7% of the genetic variants detected in GWAS studies are located in the UTRs.11,12
