Abstract: SA-OR38
Transcriptional Reprogramming by Wilms' Tumor 1 and FoxC2 Mediates a Repair Response During Podocyte Injury
Session Information
- Glomerular Diseases: Trials, Prognostic Markers, and Podocyte Biology
November 06, 2021 | Location: Simulive, Virtual Only
Abstract Time: 04:30 PM - 06:00 PM
Category: Glomerular Diseases
- 1204 Podocyte Biology
Authors
- Ettou, Sandrine S., Boston Children's Hospital, Boston, Massachusetts, United States
- Taglienti, Mary E., Boston Children's Hospital, Boston, Massachusetts, United States
- Schumacher, Valerie A., Boston Children's Hospital, Boston, Massachusetts, United States
- Kreidberg, Jordan A., Boston Children's Hospital, Boston, Massachusetts, United States
Background
We previously demonstrated a transcriptional response to injury in podocytes and identified WT1 as one of the most upstream transcription factors binding nearly all genes known to be crucial for maintenance of the glomerular filtration barrier. We now demonstrate that FoxC2 transcription factor is a major component of the response to injury, binding many of the same genes as WT1. Here, we focus on understanding WT1 and FoxC2 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 performed FoxC2 ChIP-seq from isolated podocytes. WT1 is required for the podocyte response to injury. Conditional Wt1 knockout and FoxC2 knockdown mouse models were used to decipher the transcriptional mechanism through which WT1 and FoxC2 regulate podocyte gene expression during injury, using transcriptomic approaches.
Results
WT1 is required for the podocyte response to injury. Indeed, the transient increased expression of podocytes genes in mice after injury, was abolished in the absence of Wt1. We found that FoxC2 was also actively involved during this response.
By ChIP-seq, we detect 4214 FoxC2 binding sites before injury, rising to 12,532 after ADR. In contrast to WT1, that maintains a moderate degree of binding during the later stages of injury, FoxC2 binding is essentially absent. Using a set of 48 podocyte genes encoding components of the glomerular filtration barrier, ChIP-seq analyses demonstrated that WT1 and FoxC2 both acquire novel binding sites during the early stages of injury. One co-bound site is at the Wt1 transcriptional start site, where binding of both WT1 and FoxC2 increases dramatically after injury. Furthermore, WT1 and FoxC2 may be co-immunoprecipitated and knockdown of Wt1 or FoxC2 in immortalized podocytes demonstrated their mutual dependence for binding target genes.
Conclusion
Together, these results demonstrate that WT1 and FoxC2 mediate transcriptional reprogramming during podocyte injury. This transcriptional reprogramming may be initiated by the dramatic increased binding of WT1 and FoxC2 at the Wt1 transcriptional start site after injury. Irreversible podocyte injury leading to FSGS may result from the nearly complete loss of FoxC2 binding to target genes during later stages of injury.
Funding
- NIDDK Support