Screening for modifiers of PKD severity using ENU Mutagenesis

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ABSTRACT There is abundant evidence from the analysis of human populations and mouse models that the severity of Polycystic Kidney Disease (PKD) can be modified by interacting genetic loci. The identification of these loci should provide insight into our understanding of the basic pathobiology of cystogenesis and disease progression. Importantly, they can potentially reveal novel pathways of therapeutic intervention. We have extensive experience in the characterization of a mouse model of cystic kidney disease, and specifically the investigation of strain-specific modifiers of its severity. However, the yield of proven causal genes in mouse studies of this type has been low. In contrast, we have been very successful using a different approach for novel disease gene discovery, namely mutagenesis with the chemical ethyl-nitrosourea (ENU). We have recently modified this method so that we can do our screen entirely on an inbred background, using Whole Genome Sequencing methodology for positional cloning. The recent characterization of the PKD1RC mutant mouse as having slowly progressive PKD, which is sensitive to strain-specific modifiers, compels our proposal that we use ENU mutagenesis for the generation and discovery of modifiers of PKD1-induced cystic kidney disease. To complement this phenotype-driven approach, we will also pursue an analysis of candidate loci that may modify PKD severity. We have data to suggest that Sonic Hedgehog (SHH) signaling plays a role in cystogenesis, and we will test whether the deletion of genes in this pathway affects disease severity in the PKD1RC mouse model.