Epigenetic transcriptional reprogramming by WT1 mediates a repair response during podocyte injury

Abstract

In the context of human disease, the mechanisms whereby transcription factors reprogram gene expression in response to injury are not well understood. This is particularly true in kidney podocytes, injury to which is the common and initial event in many processes that lead End Stage Kidney Disease. WT1 is a master regulator of gene expression in podocytes, binding nearly all genes known to be crucial for maintenance of the glomerular filtration barrier. Here, using purified populations of podocytes and glomeruli, we investigated WT1-mediated transcriptional reprogramming during the course of podocyte injury. Using the Adriamycin murine model of Focal Segmental Glomerulosclerosis, we discovered that podocyte injury led to increased intensity of WT1 binding and to the acquisition of new WT1 binding sites, both at previously identified target genes and at newly bound target genes, providing mechanistic insight on the transcriptional response to injury. We also observed a previously unrecognized transient increase in expression of WT1 target genes in both mice and human kidney organoids. Together, these features appear to constitute an attempt to repair the glomerular filtration barrier after podocyte injury. At later stages of injury, when proteinuria became severe, there was greatly decreased WT1 binding to most target genes. Furthermore, WT1 appeared to be required to maintain active chromatin marks at its target genes. These active marks were converted to repressive marks after loss of WT1 or Adriamycin-induced injury. This response to injury suggests that there may be a potential window of opportunity for repairing podocyte injury as a treatment for glomerular disease in humans.