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Kidney Week

Abstract: PO1980

Transcriptional Reprogramming by WT1 Mediates a Repair Response During Podocyte Injury in Mice and Human Kidney Organoids

Session Information

  • Podocyte Biology
    October 22, 2020 | Location: On-Demand
    Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Ettou, Sandrine S., Boston Children's Hospital, Boston, Massachusetts, United States
  • Jung, Youngsook L., Harvard Medical School, Boston, Massachusetts, United States
  • Miyoshi, Tomoya, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Hiratsuka, Ken, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Morizane, Ryuji, Massachusetts General Hospital, Boston, Massachusetts, United States
  • Park, Peter, Harvard Medical School, Boston, Massachusetts, United States
  • Kreidberg, Jordan A., Boston Children's Hospital, Boston, Massachusetts, United States
Background

We previously identified WT1 as one of the most upstream transcription factors regulating gene expression in podocytes, binding nearly all genes known to be crucial for maintenance of the glomerular filtration barrier. Here, we focus on understanding WT1 transcriptional mechanism in response to injury.

Methods

We used Adriamycin (ADR)-induced podocyte injury as a model for human Focal Segmental Glomerulosclerosis in mice and human kidney organoids, and a conditional Wt1 inactivated mouse model to decipher the transcriptional mechanism through which WT1 regulates podocyte gene expression during injury, using transcriptomic approaches.

Results

After injury, we observed a transient increased expression of podocyte genes in mice and human kidney organoids. Transcriptomics analyses of podocytes isolated from mTmG-Nphs2cre mice during the course of injury revealed a transient increase in the expression of crucial podocyte genes, including Nphs2, Synpo and many others, reflecting a reparative response during the early stages of injury. ChIP-seq analyses demonstrated that WT1 binds nearly 50% of known genes in podocytes, and the vast majority of genes whose expression changes during the response to injury. We identified de novo binding of WT1 that were only bound during the course of injury, and the expression of novel WT1 target genes. It appears that WT1 increases gene expression during injury through both the acquisition of novel binding sites, and increasing its binding intensity at sites bound in uninjured podocytes. Additionally, motifs predicting binding of other podocyte-specific transcription factors were highly enriched at sites where WT1 binding increased after injury. Since the DNA binding of transcription factors is modulated by chromatin accessibility, we used FACS-isolated podocytes to study epigenetic reprogramming. Both ADR-mediated podocyte injury or inducible podocyte specific inactivation of Wt1 resulted in the conversion of active to repressive histone marks at WT1-bound sites.

Conclusion

These results demonstrate that target gene binding of WT1 is highly dynamic in response to injury. WT1 directs the epigenetic regulation of gene expression, maintaining active chromatin marks at bound genes, that change to repressive marks in the absence of WT1.

Funding

  • NIDDK Support