To illustrate the application of mouse genetics in going “from mice to humans” we will now consider 4 genes from human diabetes GWAS examined in recent studies; FTO, TCF7L2, CDKAL1, and SLC30A8 (Fig. 1), all of which had not previously been considered as prominent candidates for diabetes research until uncovered by GWAS. This evidence concerns the gene TCF7L2 and diabetes mellitus.