Resequencing of genes for transforming growth factor β1 (TGFB1) type 1 and 2 receptors (TGFBR1, TGFBR2), and association analysis of variants with diabetic nephropathy

Background: Diabetic nephropathy is the leading cause of end stage renal failure in the western world. There is substantial epidemiological evidence supporting a genetic predisposition to diabetic nephropathy, however the exact molecular mechanisms remain unknown. Transforming growth factor (TGF beta 1) is a crucial mediator in the pathogenesis of diabetic nephropathy. Methods: We investigated the role of five known single nucleotide polymorphisms ( SNPs) in the TGFB1 gene for their association with diabetic nephropathy in an Irish, type 1 diabetic case (n= 272) control (n= 367) collection. The activity of TGF beta 1 is facilitated by the action of type 1 and type 2 receptors, with both receptor genes (TGFBR1 and TGFBR2) shown to be upregulated in diabetic kidney disease. We therefore screened TGFBR1 and TGFBR2 genes for genomic variants using WAVE (TM) (dHPLC) technology and confirmed variants by direct capillary sequencing. Allele frequencies were determined in forty-eight healthy individuals. Data for all SNPs was assessed for Hardy Weinberg equilibrium, with genotypes and allele frequencies compared using the chi(2) test for contingency tables. Patterns of linkage disequilibrium were established and common haplotypes estimated. Results: Fifteen variants were identified in these genes, seven of which are novel, and putatively functional SNPs were subsequently genotyped using TaqMan (TM), Invader (TM) or Pyrosequencing (R) technology. No significant differences (p > 0.1) were found in genotype or allele distributions between cases and controls for any of the SNPs assessed. Conclusion: Our results suggest common variants in TGFB1, TGFBR1 and TGFBR2 genes do not strongly influence genetic susceptibility to diabetic nephropathy in an Irish Caucasian population.