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Abstract: PO0876

Transcription Factor 21 Regulates Nephron Progenitor Cells Self-Renewal/Induction and Podocyte Development

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 500 Development, Stem Cells, and Regenerative Medicine

Authors

  • Finer, Gal, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Hayashida, Tomoko, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Souma, Tomokazu, Duke University, Durham, North Carolina, United States
  • Zhao, Xiangmin, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Liang, Xiaoyan, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Onay, Tuncer, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
  • Maezawa, Yoshiro, Chiba-ken, Chiba, Chiba, Japan
  • Quaggin, Susan E., Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
Background

Most forms of CAKUT arise from mutations in genes of kidney development. We previously showed that Transcription Factor 21 (Tcf21) regulates branching morphogenesis by downregulating GDNF. We now aim to study Tcf21 in nephron progenitor cells (NPC). During nephrogenesis, WNT9b signals to NPC through the canonical Wnt/β-catenin pathway, which promotes both self-renewal at a state of low β-catenin level, and induction at a state of high β-catenin. Following induction, β-catenin level must decrease for MET to progress. Additionally, optimal intensity of β-catenin is essential for NPC differentiation to podocytes. Hence, discrete levels of β-catenin promote disparate cell fates. It remains unclear however what drives this change and direct NPC to exit/maintain self-renewal.

Methods

Kidneys from Six2CreTcf21f/f mice were extracted for qPCR and immunohistochemistry. MK3 cells were used to study Tcf21 signaling. Recombinant Tcf21 was used for over-expression.

Results

Six2CreTcf21f/f kidneys show marked decrease in Cited1 expression from E12.5 through P0 compared to control, while still expressing normal levels of Six2, indicating decreased self-renewing NPC population. Six2CreTcf21f/f kidneys also demonstrated low Lef1 expression suggesting decreased NPC epithelialization. However, Wnt4, a marker of the pretubular aggregate, was persistently elevated in the developing nephrons of Six2CreTcf21f/f. This state of Cited1lowWnt4highLef1low in the mutants suggests arrested MET and persistently elevated β-catenin levels in the differentiating progenitors. In uninduced mesenchymal cell culture (MK3), over-expression of wild-type Tcf21 led to enhancement of genes that mark renewing NPC: Cited1, Tafa5, and Pla2g7, while over-expression of mutated-Tcf21 abrogated that enhancement, again supporting Tcf21 involvement in NPC dynamics. As to podocyte differentiation, lineage tracing of Tcf21Cre showed its expression in a subset of NPC in the cap-mesenchyme and then in developing and mature podocytes. At P0, Six2CreTcf21f/f kidneys showed very low podocin expression. This suggests that Tcf21 is required for NPC differentiation to podocytes.

Conclusion

Together, these data suggest that Tcf21 modulates Wnt/β-catenin signal intensity spatially and temporally to direct NPC toward self-renewal or differentiation.

Funding

  • NIDDK Support