Genome-wide association studies have identified many putative disease susceptibility loci in recent years [1]–[3]. This approach to studying disease has succeeded largely because of improved catalogues of human genetic variation [4] and advances in genotyping technology, but it has also been bolstered by the rise of genotype imputation methods [5]–[8], which have allowed researchers to tease increasingly subtle signals out of large and complex genetic datasets [9],[10].
