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Abstract: FR-PO772

Modeling a Recurring Wilms Tumor-Associated Mutation in Kidney Organoids

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 500 Development, Stem Cells, and Regenerative Medicine

Authors

  • Stevenson, Matthew, University of North Carolina, Chapel Hill, North Carolina, United States
  • Meza Jarquín, Marvin A., University of North Carolina, Chapel Hill, North Carolina, United States
  • O'Brien, Lori L., University of North Carolina, Chapel Hill, North Carolina, United States
Background

Wilms tumor (WT) is the most common pediatric kidney cancer and blastemal-predominant tumors represent a more lethal, chemotherapy-resistant form of WT. This tumor subtype expresses markers found only in the nephrogenic niche of the fetal kidney, suggesting it arises from a malignant transformation of these cells. Sequencing of blastemal-predominant tumors has identified a recurring single amino acid mutation, Q177R, within the conserved DNA binding domains of the closely related transcription factors SIX1/SIX2. These factors are critical for the maintenance of nephron progenitors during mammalian kidney development. Therefore, we hypothesize that this recurring mutation disrupts the regulatory networks controlled by SIX1/SIX2 resulting in the malignant transformation of nephron progenitors. Efforts to model WT in mice have proven challenging and differences in gene expression dynamics between mouse and human nephrogenesis, specifically the temporal expression of SIX1, necessitates a novel system in which to investigate the tumorigenic potential of the Q177R mutation.

Methods

IPSC-derived kidney organoids recapitulate key stages of human kidney development in vitro, resulting in the formation of complex nephron-like structures. Building upon established protocols, we have developed a modified, minimal 3D protocol to reproducibly generate kidney organoids for use as a model system. To investigate the transformative potential of the SIX1-Q177R mutation within the context of our kidney organoid system, we generated an isogenic iPSC line expressing a FLAG-tagged, mutant SIX1-Q177R protein from the endogenous SIX1 locus.

Results

ChIP-qPCR revealed proper targeting of SIX1 to its canonical DNA targets by day 5 of differentiation with significantly increased binding by day 8, recapitulating the in vivo activities of SIX1 during human nephrogenesis. Analysis of gene expression changes over the course of differentiation also revealed proper temporal expression patterns of many canonical nephron progenitor markers in our kidney organoids.

Conclusion

By combining modern genome editing techniques with our defined kidney organoid differentiation system, we have enabled the in-depth characterization of the altered regulatory landscape brought about by the SIX1-Q177R mutation throughout the earliest stages of human kidney development in a relevant in vitro model system.

Funding

  • Other NIH Support