Mapping Expression Quantitative Trait Loci

Abstract

Expression quantitative trait loci (eQTLs) are genomic loci that regulate expression levels of mRNAs or proteins.[1] Expression traits differ from most other classical complex traits in one important respect—the measured mRNA or protein trait almost always is the product of a single gene with a specific chromosomal location. eQTLs that map to the approximate location of their gene-of-origin are referred to as cis eQTLs. In contrast, those that map far from the location of their gene-of-origin gene, often on different chromosomes, are referred to as trans eQTLs. The first genome-wide mapping studies of gene expression were initiated in the late 1980s and early 1990s by Damerval and de Vienne.[2][3] They exploited then innovative 2D protein separation methods and introduced the term "protein quantity locus" or PQL (now sometimes pQTL). The advent of high-throughput array-based methods to measure mRNA abundance in the early 2000s catalyzed an impressive number of expression QTL studies in plants and animals, including humans.