Redundancy amongst interactions affecting HLA-DRB5 expression in the pre-frontal cortex. (a) Linkage disequilibrium (r2) amongst cis-SNPs (top right), amongst trans-SNPs (bottom left) and between Bonferroni significant cis-trans interacting SNPs (bottom right). The interactions are denoted as positive or negative depending on the directionality of the interaction coefficient. (b) Schematic of the relative positions of the SNPs involved in interactions. By comparing linkage disequilibrium amongst cis-SNPs, amongst trans-SNPS and the direction of the interaction effect, the 9 interactions affecting HLA-DRB5 collapse into 5 three groups of non-redundant interactions, (Group 1: rs9267873-rs2247056, rs9267873-rs6457374; Group 2: rs507778-rs2247056, rs507778-rs6457374; Group 3: rs805262-rs2247056, rs805262-rs6457374; Group 4: rs2072633-rs3093998, rs592229-rs3093998, Group 5: rs2858331-rs3093998).