Using publicly available gene expression data, we observed that SLC1A1 is robustly expressed in lymphoblastoid cell lines. This prompted us to investigate whether SLC1A1 expression constitutes a heritable trait. By analyzing 194 lymphoblastoid cell lines from 14 three-generational families,22 we determined an additive (narrow-sense or h2) heritability of 0.23 (P<.001) for SLC1A1 gene expression, with no significant sex effects when sex was included as a covariate. We then sought to identify eQTLs for SLC1A1 acting in cis within 1 Mb of the SLC1A1 genomic locus by performing a linear regression analysis of expression data on genotypes recoded as 0, 1, or 2 on the basis of minor allele occurrences. Of 2467 markers tested, 3 SNPs that were not in complete linkage disequilibrium scored a nominal P≤.02 and had the same direction of effect in both data sets (ie, positive or negative regression coefficient; r2 value, 9%-14%) (Figure 1). One of these SNPs, rs3933331, is located about 100 kb upstream of the SLC1A1 transcription initiation site, while the 2 other eQTL SNPs, rs7858819 and rs301430, are in the 3′ end of
