Abstract: TH-PO595

Lessons from Pkd1 Therapeutic Targeting Strategies in a Loss-of-Function Mouse Model

Session Information

Category: Genetic Diseases of the Kidney

  • 801 Cystic Kidney Diseases

Authors

  • Parrot, Camila, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada
  • Kurbegovic, Almira, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada
  • Lake, Jennifer, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada
  • Yao, Guanhan, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada
  • Trudel, Marie, Institut de Recherches Cliniques de Montréal, Montréal, Quebec, Canada
Background

Autosomal dominant polycystic kidney disease (ADPKD) causes renal and extrarenal phenotypes. The PKD1 gene responsible for most cases of ADPKD has a developmentally and temporally regulated expression pattern. While CRISPR-Cas as a therapeutic strategy for PKD is attractive, the high frequency of off-targets preclude clinical application. Because microscopic cysts below clinical detection are likely formed in utero in ADPKD kidneys (Grantham et al CJASN 2010,2012), we targeted Pkd1 at early stage in mouse model to assess for long-term treatment. Pkd1 null mouse model that display severe renal cysts and die by birth, were used to assess whether wild type Pc1 from 2 series of transgenic lines prevent cyst formation.

Methods

One mating overexpressing Pc1 was generated with 2 systemic Pkd1TAG mouse lines and the second with 2 renal-specific SBPkd1TAG mice. RNA and proteins in kidneys and pancreas were assessed along with histomorphologic and cellular longitudinal analysis.

Results

Pkd1-/- mice crossed into each of the Pkd1TAG transgenic lines escaped perinatal lethality. These mice exhibit no renal or pancreatic phenotypes in the first few months of age. Thus, the Pkd1TAG transgene produced a functional protein with proper transgene regulation. Pkd1TAG;Pkd1-/- mice at >8mo developed however renal cysts but milder than the parental transgenic line consistent with their Pkd1 overexpression and a gene-dosage pathogenic mechanism. Pkd1-/- mice mated to SBPkd1TAG renal specific expressors avoided neonatal death but consistently, developed renal (kidney/body weight 2.3 fold that of normal mice) and pancreatic cysts. Despite Pc1 ~7 and 15-fold overexpression, deaths occur at P10-P15 with the mild Pc1 expressor and ~3 mo in the high expressor, indicating that renal cysts likely result from differential tubular response: insufficient expression and/or overexpression of Pc1. Collectively, these results demonstrate that early Pc1 expression can delay cystogenesis and extend mouse lifespan, and revealed that Pc1 re-expression requires highly controlled spatiotemporal regulation.

Conclusion

Maintenance of tightly regulated PKD1/PC1 expression will be a major clinical challenge as PC1 expression varies between renal cell types and age. Presently, targeting PC1 in ADPKD is a double-edge sword and cannot practically serve as a useful therapeutic target.

Funding

  • Government Support - Non-U.S.