A study by Plagnol et al. (2009) focused on a potentially causal relationship between the 12q13 locus, associated with type 1 diabetes, and the nearby gene RPS26. The authors reasoned that if the locus in question increased disease susceptibility via regulation of RPS26 expression, then the effect sizes inferred from the GWAS and the RPS26 eQTL (i.e., odds ratios and regression coefficients, respectively) should be proportional. Here, RPS26 is linked to type 1 diabetes mellitus.