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Abstract: FR-OR16

TGFβ Signaling Regulates Renal Patterning via Cadm1 During Nephrogenesis

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 600 Development, Stem Cells, and Regenerative Medicine

Authors

  • Qubisi, Sara, The Hospital for Sick Children, Toronto, Ontario, Canada
  • Rosenblum, Norman D., The Hospital for Sick Children, Toronto, Ontario, Canada
Background

Impaired nephrogenesis affects kidney health, causing childhood CKD and increasing CKD risk in adults. Foxd1+ kidney stromal cells regulate nephron development by interacting with Six2+ nephrogenic precursors. Previously, we (Rowan CJ et al, Development, 2018) demonstrated that Hedgehog-GLI signaling in Foxd1+ stromal cells is required to promote murine nephrogenesis through TGFβ signaling, specifically via promoting the transformation of mesenchymal cells into epithelial cells (MET) in the Six2+ nephrogenic zone. However, the underlying molecular mechanisms that guide MET are incompletely defined. Here we aim to define molecular mechanisms by which TGFβ signaling regulates nephrogenesis.

Methods

Whole-kidney RNA seq and single-cell RNA seq to examine Tgfβr2 deficiency in Foxd1+ stromal and Six2+ nephrogenic kidneys. We validated the bioinfrmatics data through immuno-staining and Western blot. Compound mutant mice were generated to investigate the deficiency of Cadm1 alone or both Tgfβr2 and Cadm1, followed by histological analysis, immunostaining, and nephron quantitation.

Results

Whole-kidney RNA seq (n=4) and scRNA seq (n=169 cell,P<0.001) in Foxd1+ stromal and Six2+ nephrogenic Tgfβr2-deficient kidneys identified Cadm1 (P<0.00003,P<0.0013) in Foxd1+stromal cells as a TGFβ signaling downstream target. Western blot analysis in HEK-T293 cells (n=2) demonstrated that treatment with TGFβ1 induced CADM1 expression in a dose-dependent manner. Kidney tissue with Stromal and/or nephrogenic cell deficiency of Cadm1 exhibited normal nephrogenesis (n=2-3,P<0.01). Kidney tissue with deficiency of both Tgfβr2 and Cadm1 in Foxd1+ stroma exhibited renal hypodysplasia characterized by 32% reduction in kidney:body weight (n=6,P<0.0001), a 35% reduction in nephron number (n=3,P<0.05), expansion of Six2+ cells/UB tip (n=2,P<0.05),and loosely packed cortex and irregular stromal pattern (n=3). Similarly, kidney tissue with deficiency of both Tgfβr2 and Cadm1 in Six2+ nephrogenic cells exhibited renal hypodysplasia characterized by a 27% reduction in kidney:body weight (n=3,P<0.01), a 48% reduction in nephron number (n=2,P<0.05) and expansion of Six2+ cells/UB tip (n=3, P<0.01).

Conclusion

We conclude that Cadm1 is required for normal nephrogenesis in mice. Further, our data suggest that CADM1 may play a role in regulating the epithelialization of nephrogenic precursors under the influence of TGFβ signaling

Funding

  • Government Support – Non-U.S.