Imputation of SNPs in the KCNJ6 region was performed using the program BEAGLE version 3.3.1 (Browning & Browning 2009) (http://www.sph.umich.edu/csg/abecasis/MaCH/). We used reference data from the European popultaion in the August 2010 release of the 1000 Genomes Project provided with the Beagle release for our European American sample. SNPs with a final r2, the estimated squared correlation between the estimated allele dosage and the true allele dosage, >0.30 were used. For individual-level genotype data, we retained genotypes having a probability ≥80% (from the gprob metric in Beagle); otherwise that genotype was set to missing. To account for uncertainty, we used the mean of the distribution of imputed genotypes, which corresponds to an expected allelic or genotypic count (dosage) for each individual. Subsequently, association tests of the Fz theta ERO phenotype were performed.
