Identification of sequence variants robustly associated with predisposition to diabetic kidney disease (DKD) has the potential to provide insights into the pathophysiological mechanisms responsible. We conducted a genome-wide association study (GWAS) of DKD in type 2 diabetes (T2D) using eight complementary dichotomous and quantitative DKD phenotypes: the principal dichotomous analysis involved 5,717 T2D subjects, 3,345 with DKD. Promising association signals were evaluated in up to 26,827 subjects with T2D (12,710 with DKD). A combined T1D+T2D GWAS was performed using complementary data available for subjects with T1D, which, with replication samples, involved up to 40,340 subjects with diabetes (18,582 with DKD). Analysis of specific DKD phenotypes identified a novel signal near (rs9942471, = 4.5 × 10) associated with microalbuminuria in European T2D case subjects. However, no replication of this signal was observed in Asian subjects with T2D or in the equivalent T1D analysis. There was only limited support, in this substantially enlarged analysis, for association at previously reported DKD signals, except for those at and, both associated with estimated glomerular filtration rate. We conclude that, despite challenges in addressing phenotypic heterogeneity, access to increased sample sizes will continue to provide more robust inference regarding risk variant discovery for DKD.

Almost all genomic studies of breast cancer have focused on well-established tumours because it is technically challenging to study the earliest mutational events occurring in human breast epithelial cells. To address this we created a unique dataset of epithelial samples ductoscopically obtained from ducts leading to breast carcinomas and matched samples from ducts on the opposite side of the nipple. Here, we demonstrate that perturbations in mRNA abundance, with increasing proximity to tumour, cannot be explained by copy number aberrations. Rather, we find a possibility of field cancerization surrounding the primary tumour by constructing a classifier that evaluates where epithelial samples were obtained relative to a tumour (cross-validated micro-averaged AUC = 0.74). We implement a spectral co-clustering algorithm to define biclusters. Relating to over-represented bicluster pathways, we further validate two genes with tissue microarrays and in vitro experiments. We highlight evidence suggesting that bicluster perturbation occurs early in tumour development.

Epigenetic regulation of oxidative stress is emerging as a critical mediator of diabetic nephropathy. In diabetes, oxidative damage occurs when there is an imbalance between reactive oxygen species generation and enzymatic antioxidant repair. Here, we investigated the function of the histone methyltransferase enzyme enhancer of zeste homolog 2 (EZH2) in attenuating oxidative injury in podocytes, focusing on its regulation of the endogenous antioxidant inhibitor thioredoxin interacting protein (TxnIP). Pharmacologic or genetic depletion of EZH2 augmented TxnIP expression and oxidative stress in podocytes cultured under high-glucose conditions. Conversely, EZH2 upregulation through inhibition of its regulatory microRNA, microRNA-101, downregulated TxnIP and attenuated oxidative stress. In diabetic rats, depletion of EZH2 decreased histone 3 lysine 27 trimethylation (H3K27me3), increased glomerular TxnIP expression, induced podocyte injury, and augmented oxidative stress and proteinuria. Chromatin immunoprecipitation sequencing revealed H3K27me3 enrichment at the promoter of the transcription factor Pax6, which was upregulated on EZH2 depletion and bound to the TxnIP promoter, controlling expression of its gene product. In high glucose-exposed podocytes and the kidneys of diabetic rats, the lower EZH2 expression detected coincided with upregulation of Pax6 and TxnIP. Finally, in a gene expression array, TxnIP was among seven of 30,854 genes upregulated by high glucose, EZH2 depletion, and the combination thereof. Thus, EZH2 represses the transcription factor Pax6, which controls expression of the antioxidant inhibitor TxnIP, and in diabetes, downregulation of EZH2 promotes oxidative stress. These findings expand the extent to which epigenetic processes affect the diabetic kidney to include antioxidant repair.