Kidney Week

Abstract: TH-OR63

Inactivation of Ire1alpha Endoribonuclease Domain Slows Down ADPKD in Orthologous Mouse Models

Session Information

• Investigations in Polycystic and Tubulointerstitial Kidney Diseases
  November 02, 2023 | Location: Room 105, Pennsylvania Convention Center
  Abstract Time: 04:48 PM - 04:57 PM

Category: Genetic Diseases of the Kidneys

• 1201 Genetic Diseases of the Kidneys: Cystic

Authors

• Bhardwaj, Rishi, Yale School of Medicine, New Haven, Connecticut, United States

Rishi Bhardwaj, PhD

• Volpe, Isabel, Yale School of Medicine, New Haven, Connecticut, United States

Isabel Volpe,

• Yilmaz, Duygu Elif, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Duygu Elif Yilmaz,

• Pioppini, Carlotta, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Carlotta Pioppini,

• Roy, Kasturi, Yale School of Medicine, New Haven, Connecticut, United States

Kasturi Roy,

• Rehman, Michael, Yale School of Medicine, New Haven, Connecticut, United States

Michael Rehman,

• Cai, Yiqiang, Yale School of Medicine, New Haven, Connecticut, United States

Yiqiang Cai,

• Krappitz, Matteus, Charite Universitatsmedizin Berlin, Berlin, Berlin, Germany

Matteus Krappitz,

• Somlo, Stefan, Yale School of Medicine, New Haven, Connecticut, United States

Stefan Somlo,

• Fedeles, Sorin V., Yale School of Medicine, New Haven, Connecticut, United States

Sorin V. Fedeles,

Background

The Ire1alpha-XBP1 pathway is the most conserved UPR branch from yeast to mammals. Our previous studies (abstract WCN23-2042) showed that genetic inactivation of XBP1 leads to significant improvement in disease severity in neonatal and adult Pkd1-dependent ADPKD mouse models through specific apoptosis of cystic cells. The endoribonuclease domain of Ire1α splices an intron from the XBP1 mRNA leading to the formation of active XBP1 which acts as a transcription factor to mitigate ER stress. Here we investigated whether a point mutation in the endoribonuclease domain of Ire1alpha can recapitulate the genetic XBP1 inactivation rescue in the context of orthologous ADPKD mouse models.

Methods

We generated an in vivo Ire1alpha endoribonuclease dead point mutation (K907A) via CRISPR/Cas9. We crossed the Ire1alpha mutant with Pkd1 deficient early and adult models and assessed the impact on disease severity via morphological and functional parameters. Finally, we examined the effect of XBP1 inactivation in bile ducts in polycystic liver disease models due to polycystin-1 deletion.

Results

We confirmed that the K907A mutation in the endoribonuclease domain of Ire1alpha leads to impaired XBP1 splicing activity as seen via western blotting. We generated Ire1alpha ^K907A animals and confirmed homozygous embryonic lethality. We then used Ire1alpha ^K907A/flox animals and crossed them with either Pkd1^flox/flox;Pkhd1-Cre (early model) or Pkd1^flox/flox:Pax8^rtTA;Tet-OCre (adult model) mice to generate experimental Ire1alpha^K907A/flox ;Pkd1^flox/flox;Pkhd1-Cre or Ire1^K907A/flox;Pkd1^flox/flox:Pax8^rtTA;Tet-OCre mice. The mice showed significantly improved kidney to body weight ratio (KW/BW) compared with the Pkd1-SKO mice (0.095±0.011 vs 0.136±0.022, **p=0.008, early model; 0.088±0.031 vs 0.149±0.043, *p=0.027, adult model). Finally, when XBP1 was inactivated concomitantly with Pkd1 in bile ducts using Ubc-Cre, a dramatic impact on cystic disease severity was observed compared with the single Pkd1 KO animals.

Conclusion

Our results demonstrate that specific inactivation of the Ire1alpha endoribonuclease domain upstream of XBP1 is beneficial in slowing down ADPKD progression. Ire1alpha endoribonuclease inhibitors may serve as potential starting points for development of ADPKD therapeutics.

Funding

• NIDDK Support