A genetic variant that influences a particular gene-expression level is known as expression quantitative trait loci (eQTL). Two studies using eQTL analysis in primary bone cell cultures discovered numerous eQTLs associated with BMD [18,19]. Kwan et al. found an eQTL (rs136564) regulated the expression of a novel transcript of FAM118A, and this eQTL was also found to be associated with BMD by GWAS analysis [19]. There are many other studies that have attempted to assess whether a SNP detected by GWAS was also an eQTL [20]; however most of them have analyzed the GWAS data and eQTL data in two sequential and separate steps rather than in an integrative manner [21]. Zhu et al. recently proposed an integrative method called summary data–based Mendelian randomization (SMR) that integrates independent GWAS summary statistics data with eQTL data from whole blood tissue to identify potential functionally relevant genes at the loci identified in GWAS and to identify novel trait-associated genes for five complex traits [22], and further applied the method to the analyses of another 28 traits [23]. It has been shown that
