producing primer extension products. MALDI-TOF SNP genotyping was performed at the Genome Analysis Center (GAC) facility of the Helmholtz Zentrum Munich, Germany. All primer sequences used are available upon request. The individual-wise mean call rate over all plates and these SNPs was above 98%. Genotypes of all SNPs were in HWE (p<0.05). To exclude genotyping errors in the German studies, we re-genotyped the two tagging SNPs (rs1545843 and rs1031681) in more than 95% and 80% of individuals in the MARS discovery GWAS and the German recurrent depressive replication sample, respectively using the MALDI-TOF platform. We obtained a genotype concordance rate with the genotypes produced by the Illumina assays of >99.9%. In the U.K. studies, all subjects had been genotyped on the Illumina 610k-Quad Beadchips. In the ERF study 1000 individuals were genotyped with Illumina 300k, 100 individuals with Illumina 370k arrays and 200 individulas with the Affymetrix 250k array. The Rotterdam study samples were genotyped by using the Illumina 550k arrays and the additional MARS samples using the Illumina 610k array.
