Kidney Week

Abstract: SA-PO479

Persistent Upregulation of Homologous Recombination Repair Signalling in Cystic Epithelial Cells in Autosomal Dominant Polycystic Kidney Disease (ADPKD)

Session Information

• Cystic Kidney Diseases: Basic/Translational
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1001 Genetic Diseases of the Kidneys: Cystic

Authors

• Zhang, Jennifer, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Jennifer Zhang,

• Saravanabavan, Sayanthooran, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Sayanthooran Saravanabavan,

• Munt, Alexandra, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Alexandra Munt,

• Sangadi, Irene, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Irene Sangadi,

• Wong, Annette, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Annette Wong,

• Harris, Peter C., Mayo Clinic, Rochester, Minnesota, United States

Peter C. Harris,

• Harris, David, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

David Harris,

• Wang, Yiping, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Yiping Wang,

• Rangan, Gopi, Westmead Institute for Medical Research, The University of Sydney, Westmead, New South Wales, Australia

Gopi Rangan,

Background

In ADPKD, homologous recombination repair (HRR) of the PKD allele in response to DNA damage might explain the postnatal reduction in gene dose and triggering of focal kidney cyst formation. In this study, the hypothesis that HRR signaling is increased in ADPKD and correlates with kidney cyst formation, was investigated.

Methods

Markers of HRR [H2AX, γH2AX, phosphorylated Ataxia Telangiectasia and Rad3-related; pATR and AT Mutated; pATM] were assessed in immortalised ADPKD (WT9-7 and WT9-12) and normal (HK-2) kidney cells; Pkd1^RC/RC mice (1, 3, 6, 9 and 12 months), and end-stage human ADPKD. In addition, the expression of genes encoding proteins upstream (n=88) and downstream of HRR (n=355) was determined from normal and ADPKD kidney tissue [the latter divided into minimal cystic tissue, (MCT), small cysts (SC), medium cysts (MC) and large cysts (LC)] using public transcriptomic datasets (GSE7869; GSE9493).

Results

In vitro, pATR increased 1.7- and 2.2-fold in unstimulated WT9-7 and WT9-12 cells respectively compared to HK-2 cells (P<0.05). Similarly, pATM increased 9.6- (WT9-7) and 6.8-fold (WT9-12) compared to HK-2 cells (P<0.05). In Pkd1^RC/RC mice, cyst-lining epithelial cells (CECs) were positive for pATR and γH2AX at all timepoints, with higher frequency at 1 month of age. In end-stage human ADPKD tissue, CECs of kidney cysts were positive diffusely for pATR and pATM. Further analysis showed that dysregulation of HRR-related genes (>1.5-fold, q<0.05) varied by cyst size. The percentage of dysregulated genes encoding upstream HRR mediators (including MRN, TOPBP1 and RPA1) increased 22% (in MCT), 47% (in SC) and 52% (in LC), compared to control kidneys. Similarly, genes encoding downstream HRR factors were also dysregulated according to kidney cyst size [MCT (12%), SC (36%), MC (37%) and LC (45%)]. ATR was highest in MCT (1.6-fold; q=0.01), and H2AX increased 1.4-fold (q=0.07) in MCT and 3.0-fold in LC (q=0.0001).

Conclusion

Kidney cystic epithelial cells exhibit DNA damage and the persistent upregulation of HRR signalling which correlates with cyst size. These data suggest that low-dose inhibition of HRR pathways using sub-lethal dose of ATR or ATM inhibitors could be used to selectively target kidney cyst growth.

Funding

• Government Support - Non-U.S.