Markov Chain based haplotyper (MACH 1.0.16) was used to impute non-assayed genotypes for blood and brain datasets independently using the June 2010 release of the 1000 Genomes Project build-36 reference panel, using default settings for MACH. Imputed SNPs were excluded from the analysis if their minor allele frequency (MAF) was < 0.01 and if their r2 was < 0.3.