Supplementary Material for: No Effect of Genome-Wide Significant Schizophrenia Risk Variation at the <b><i>DRD2</i></b> Locus on the Allelic Expression of <b><i>DRD2</i></b> in Postmortem Striatum

A genome-wide significant association has been reported between non-coding variants at the dopamine D2 receptor (<i>DRD2</i>) gene locus and schizophrenia. However, effects of identified schizophrenia risk alleles on <i>DRD2</i> function are yet to be demonstrated. Using highly sensitive measures of allele-specific expression, we have assessed <i>cis</i>-regulatory effects associated with genotype at lead SNP rs2514218 on <i>DRD2</i>expression in the adult human striatum. No significant differences were observed in the extent of allelic expression imbalance between samples that were genomic heterozygotes for rs2514218 (where <i>cis</i>-regulatory effects of the risk allele are compared with those of the non-risk allele within individual subjects) and samples that were homozygous for rs2514218 (where <i>cis</i>-regulatory effects of this SNP on each expressed <i>DRD2</i> allele will be equal). We therefore conclude that rs2514218 genotype is not associated with large effects on overall <i>DRD2</i> RNA expression, at least in postmortem adult striatum. Alternative explanations for the genetic association between this variant and schizophrenia include effects on <i>DRD2</i> that are transcript specific, restricted to minor <i>DRD2</i>-expressing cell populations or elicited only under certain physiological circumstances, or mediation through effects on another gene (or genes) at the locus.