Although our study was not designed to explicitly investigate the impact of copy number variation on glycemic traits, we took advantage of existing data44 to investigate whether any of our lead SNPs are in LD with common, diallelic copy number polymorphisms (CNPs) mapping within a 1Mb window. Of the FG loci, only DGKB/TMEM195 has a validated, common CNP affecting sequence within 1 Mb of the index SNP44. Despite the proximity of this CNP to the associated SNP (~25 kb), the CNP is essentially uncorrelated with the index SNP (r2=0.01 in HapMap CEU) and is therefore unlikely to explain the observed FG association.
