Abstract: SA-PO193

Transcriptional Reprogramming by Wilms’ Tumor 1 and FoxC2 Mediates a Repair Response during Podocyte Injury

Session Information

  • Glomerular: Cell Biology
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Glomerular

  • 1003 Glomerular: Cell Biology

Authors

  • Ettou, Sandrine S., Boston Childrens Hospital- Harvard Medical School, Boston, Massachusetts, United States
  • Jung, Youngsook L., Harvard Medical School, Boston, Massachusetts, United States
  • Kann, Martin, Kidney Research Center Cologne , Cologne, Germany
  • Park, Peter, Harvard Medical School, Boston, Massachusetts, United States
  • Kreidberg, Jordan A., Boston Childrens Hospital- Harvard Medical School, Boston, Massachusetts, United States
Background

Foot process effacement and proteinuria, representing a breakdown of the glomerular filtration barrier (GFB), may be caused by decreased expression of key podocyte proteins. We previously reported a Wilms’ tumor-1 (WT1) ChIP-Seq study that identified components of the GFB and many other important podocyte genes as WT1 target genes. Many WT1 target genes in podocytes also appear to be bound by FoxC2, including Nphs2, and Synpo. In the present study we demonstrate that WT1 and FoxC2 transcriptionally program a repair response after podocyte injury induced by Adriamycin.

Methods

We used ChIP-Seq to study the DNA binding of WT1 and Foxc2 to target genes in normal podocytes. We used Adriamycin-induced podocyte injury as a model for human FSGS. WT1 and FoxC2 binding was determined by direct ChIP-qPCR at time points after injury using isolated glomeruli from 3, 5 and 7 days post-injection or control Balb/C mice.

Results

Our ChIP-Seq results demonstrate that WT1 and FoxC2 have multiple binding sites at target genes including Nphs2 and Synpo. We previously observed that after the onset of heavy proteinuria, Nphs2 and Synpo expression decreases, as does WT1 and FoxC2 binding to their respective target sites. However, in examining mice prior to, or during the early phase of proteinuria, WT1 and FoxC2 binding to target genes actually undergoes a transient increase at specific enhancer and promoter sites, and Nphs2 and Synpo expression dramatically increases. Using immortalized podocytes, we also demonstrate that WT1 and FoxC2 binding to target genes is interdependent and that knockdown of WT1 or Adriamycin treatment results in epigenetic silencing of the Nphs2 and Synpo genes.

Conclusion

Thus, our results reveal a previously unrecognized repair attempt in podocytes immediately after Adriamycin injury mediated by WT1 and FoxC2 to transcriptionally activate target genes required to maintain the GFB. In the Adriamycin model this repair attempt is ultimately unsuccessful, but transcriptional reprogramming may represent a therapeutic modality to maintain the GFB after podocyte injury.

Funding

  • NIDDK Support