For heritability calculations, we extracted lymphoblastoid cell line SLC1A1 gene expression values (probe No. 213664_at) from the Gene Expression Omnibus data set GSE1485.22 All individuals had a “present” call for this probe; technical replicates were averaged and then log2-transformed. Family structures for the 14 three-generational families represented in this data set were obtained from the Centre d'Etude du Polymorphisme Humain database (http://www.cephb.fr/en/cephdb/browser.php). Pedigree and expression data were then analyzed with the Sequential Oligogenic Linkage Analysis Routines software package by performing a standard quantitative genetic analysis.23 The residual kurtosis of 0.125 was within the normal range.
