Barbara C. Hansen, Rania Shamekh, Ola Hansson, Peter Almgren, Temuri Budagov, Ellen Linden, Jeffrey Pessin and Gil Atzmon
To examine the genetic basis of the spontaneous development of Type 2 diabetes mellitus (T2DM), we have conducted an initial genome wide association study (GWAS) using Affymetrix 6.0 gene chip arrays on 8 normal (Controls), and 14 insulin resistant(IR)/prediabetic(preDM)/T2DM rhesus monkeys ( Macaca mulatta ). Both IR/preDM and T2DM were classified as cases as they could be clearly defined in this model as either in the early progression toward overt DM or already overtly diabetic. The successful call rate on all chip assays averaged 91.9% with high heterozygosity (42%), demonstrating the project applicability for genotyping the rhesus monkey using the human platform. Principal component analysis classified the groups accurately according to their source – i.e. case or control. Five SNPs (Chr 18, and 1 of the human and rhesus genomes) passed the tests for multiple comparison correction and were of complete homology between the rhesus monkey and human SNPs. We identified on our Affymetrix 6.0 array 9 out of the reported 18 SNPs associated with T2DM by prior GWAS in humans (candidate human genome sequence polymorphisms with T2DM), that were present on the 6.0 array. Eight were of the same genotype, and in one SNP representing the WFS1 gene all monkeys except for one control, carried the non-ancestral allele at this position. Resequencing of the 4 most significant SNPs in 51 additional NPH subjects revealed a SNP in the same location as in human that was of significantly higher prevalence in T2DM animals and two others that were at a different location then the homolog human SNPs and were not differently distributed among the NHPs T2D patients and controls. Expression levels (measured in heart, liver and muscle) of these four candidate genes demonstrated reduced expression of CBLN2 compared to normal animals following adjustments. In addition, CBLN2 SNPs were significantly associated with HOMA-IR in patients from a Finland and Sweden Type 2 diabetes GWAS. These data demonstrate the successful use of human SNP platforms to identify genetic variants associated with T2DM in rhesus monkeys.