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Expression quantitative trait loci (eQTLs) are genomic loci that contribute to variation in expression levels of mRNAs. == Distant and local, trans- and cis-eQTLs, respectively == 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 local eQTLs. In contrast, those that map far from the location of their gene of origin, often on different chromosomes, are referred to as distant eQTLs. Often, these two types of eQTLs are referred to as cis and trans, respectively, but these terms are best reserved for instances when the regulatory mechanism (cis vs. trans) of the underlying sequence has been established. The first genome-wide study of gene expression was carried out in yeast and published in 2002. Many expression QTL studies followed in plants and animals, including humans. The initial wave of eQTL studies employed microarrays to measure genome-wide gene expression; more recent studies have employed massively parallel RNA sequencing. Some cis eQTLs are detected in many tissue types but the majority of trans eQTLs are tissue-dependent (dynamic). eQTLs may act in cis (locally) or trans (at a distance) to a gene. The abundance of a gene transcript is directly modified by polymorphism in regulatory elements. Consequently, transcript abundance might be considered as a quantitative trait that can be mapped with considerable power. These have been named expression QTLs (eQTLs)〔Cookson et al. Nat Rev Genet. 2009 Mar;10(3):184-94.〕 The combination of whole-genome genetic association studies and the measurement of global gene expression allows the systematic identification of eQTLs. By assaying gene expression and genetic variation simultaneously on a genome-wide basis in a large number of individuals, statistical genetic methods can be used to map the genetic factors that underpin individual differences in quantitative levels of expression of many thousands of transcripts.〔Cookson et. al Nat Rev Genet. 2009 Mar;10(3):184-94〕 Studies have shown that single nucleotide polymorphisms (SNPs) reproducibly associated with complex disorders as well as certain pharmacologic phenotypes are significantly enriched for eQTLs relative to frequency-matched SNPs. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Expression quantitative trait loci」の詳細全文を読む スポンサード リンク
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