Further evidence for the association of MMP9 with nephropathy in type 2 diabetes and application of DNA pooling technology to candidate gene screening

Background: Diabetic nephropathy is characterised by extracellular matrix (ECM) expansion, a key modulator of which is TGF-β1. Glucose-stimulated transcriptional activation of the TGF-β1 gene is an important component of the pathogenesis of nephropathy, following which latent TGF-β1 protein is synthesised. Matrix metalloproteinase 9 (MMP9) remodels the ECM and has been implicated in TGF-β1 activation. The ECM glycosaminoglycan hyaluronan (HA) influences TGF-β1 generation and can modulate its signal transduction activity; renal HA is synthesised by HA synthases HAS2 and HAS3. Methods: We report the first screening of the genes encoding HAS2 and HAS3 for sequence variants predisposing to nephropathy in UK type 2 diabetes patients, together with the MMP9 and TGF-β1 genes. Also for the first time, we used validated DNA pools to carry out association analyses of single nucleotide polymorphisms on nephropathic and non-nephropathic cohorts from a total of 199 type 2 diabetes patients, to increase the throughput and decrease the cost of genotype analysis. Results: None of the 23 single nucleotide polymorphisms analysed in DNA pools were found to be associated with diabetic nephropathy. However, genotyping of alleles at the MMP9 promoter microsatellite locus D20S838 in individual genomic DNA samples supported previous evidence of association between this locus and diabetic nephropathy. Conclusions: The use of DNA pooling technology increased the throughput and decreased the cost of our association analysis of nephropathy in our type 2 diabetes sample, which demonstrated sufficient sensitivity to support previous positive findings of association with a microsatellite in the MMP9 promoter region.