Five Linkage Regions Each Harbor Multiple Type 2 Diabetes Genes in the African American Subset of the GENNID Study

We previously localized type 2 diabetes (T2D) susceptibility genes to five chromosomal regions through a genome-wide linkage scan of T2D and age of diagnosis (AOD) in the African American subset of the GENNID sample. To follow up these findings, we repeated the linkage and association analysis using genotypes on an additional 9,203 fine-mapping SNPs selected to tag genes under the linkage peaks. In each of the five regions, we confirmed linkage and inferred the presence two or more susceptibility genes. The evidence of multiple susceptibility genes comprised: 1) multiple linkage peaks in four of the five regions; 2) association of T2D and AOD with SNPs within 2 or more genes in every region. The associated genes included 3 previously reported to associate with T2D or related traits (GRB10, NEDD4L, LIPG), and 24 novel candidate genes including genes in lipid metabolism (ACOXL) and cell-cell and cell-matrix adhesion (MAGI2, CLDN4, CTNNA2).