Genetic variation in the human winged helix/forkhead transcription factor gene FOXC2 in Pima Indians

FOXC2 is a winged helix gene that has been shown to counteract obesity, hypertriglyceridemia, and diet-induced insulin resistance in rodents. Therefore, FOXC2 was analyzed as a candidate gene for susceptibility to type 2 diabetes in Pima Indians. Four variants were identified by sequencing the coding region, as well as 638 bp of the 5' region and 300 bp of the 3' region of the gene. Two single nucleotide polymorphisms (SNPs) were found in the putative promoter region, a C-512T transition and a G-350T. In addition, two SNPs were found in the 3' region, a C1548T and a C1702T. The G-350T and the C1702T variants were in complete linkage disequilibrium, and the C1548T variant was relatively rare; therefore, only the C-512T and G-350T variants were additionally genotyped in 937 full-blooded Pima Indians. Neither of these polymorphisms were associated with type 2 diabetes; however, the C-512T variant was associated with BMI (P = 0.03) and percentage of body fat (P = 0.02) in male and female Pima subjects, as well as with basal glucose turnover and fasting plasma triglycerides in women. Our data indicate that variation in FOXC2 may have a minor role in body weight control and seems to be involved in the regulation of basal glucose turnover and plasma triglyceride levels in women, but this gene does not significantly contribute to the etiology of type 2 diabetes in Pima Indians.