Abstract: TH-PO365

TGFβ Signals to Chromatin via Direct Interaction of Smad3 with the Polycomb Repressive Complex during the Determination of Renal Epithelial Cell Fate

Session Information

Category: Cell Biology

  • 201 Cell Signaling, Oxidative Stress

Authors

  • Andrews, Darrell C, UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • Dodd, Thomas K., UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • Davis, Jessica, UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • Kennedy, Ciarán F, UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • Brennan, Eoin P., UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • McEvoy, Caitriona M., UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • Conlon, Peter J., Beaumont Hospital, Dublin 9, Co Dublin, Ireland
  • Godson, Catherine, UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
  • Crean, John, UCD Conway Institute of Biomolecular and Biomedical Science, Belfield, Dublin 4, Ireland
Background

TGFβ resides at the centre of therapeutic approaches for the treatment of renal fibrosis, however despite significant efforts in this area, few intervention studies have demonstrated clinical efficacy. At the core of this issue remains a fundamental gap in our knowledge of how TGFβ signalling converges and interacts with transcriptional machinery to regulate gene expression. We recently demonstrated that silencing of the TGFβ type II receptor and repression of Smad2/3 signalling by miR302 promotes the acquisition of plasticity, suggesting that TGFβ signalling to chromatin plays a critical role in determining renal cell fate decisions.

Results

Here, we have identified and characterized a novel direct interaction between Smad3 and EZH2, the enzymatic component of the PRC2 complex, during fate specification and TGFβ mediated epithelial dedifferentiation. Using iPSC derived renal organoids we established that targeting the interaction between Smad3 and EZH2 protected against TGFβ mediated tubular epithelial differentiation and loss of apical basolateral polarity. We interrogated the ChIP-Seq data (GSE75297) in which embryonic stem cells were differentiated by exposure to activin, identifying 2882 Smad3 peaks after 48h treatment with Activin of which 1618 mapped to Gene IDs. Smad3 peaks were significantly enriched for Oct/Sox motifs in ESCs whereas in ESCs treated with Activin, Smad3 peaks were prominently enriched for Nanog; 816/2112 peaks contained Nanog motifs, 243 of which mapped to known superenhancers, suggesting cooperativity between Smad3/PRC2 and superenhancer repression in the determination of cell fate. A number of these genes were also identified by RNA-seq as significantly differentially regulated in patients with chronic kidney disease (CKD).

Conclusion

We propose that this complex forms a molecular switch that regulates promoter access through epigenetic mechanisms and controls gene silencing, informing the fundamental mechanisms through which subsets of genes are switched on and off during fate specification and the pathogenesis of CKD.

Funding

  • Government Support - Non-U.S.