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Kidney Week

Abstract: PO1589

Super-Resolution Imaging of the Filtration Barrier Suggests a Role for Podocin R229Q in Genetic Predisposition to Glomerular Disease

Session Information

Category: Genetic Diseases of the Kidneys

  • 1002 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Butt, Linus, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Unnersjö-Jess, David, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Höhne, Martin, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Hahnfeldt, Robert, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Reilly, Dervla, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Rinschen, Markus M., Center for Mass Spectrometry and Metabolomics, The Scripps Research Institute, La Jolla, California, United States
  • Plagmann, Ingo, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Brinkkoetter, Paul T., Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Brismar, Hjalmar, Royal Institute of Technology, Stockholm, Sweden
  • Blom, Hans, Royal Institute of Technology, Stockholm, Sweden
  • Schermer, Bernhard, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
  • Benzing, Thomas, Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
Background

Breakdown of the three-layered glomerular filtration barrier is a leading cause of end-stage kidney disease. Whereas extensive research led to a growing understanding of hereditary glomerular diseases in children, most adult patients lack a genetic diagnosis. p.R229Q is a common missense variant in NPHS2, the gene encoding podocin, and it is associated with albuminuria in the general population. However, epidemiological studies suggest that p.R229Q is only disease causing in trans-association to additional genetic alterations.

Methods

We assessed the predisposition of p.R229Q to glomerular disease by introducing the equivalent point mutation in mice using CRISPR/Cas9-mediated genome editing. By applying super-resolution STED microscopy and functional measurements, we characterized the phenotype of PodR231Qmice. Additionally, we evaluated the podocinR231Qprotein stability in human cultured podocytes.

Results

Although PodR231Q/wildtypemice do not develop overt glomerular disease, super-resolution microscopy and morphometric analyses revealed ultrastructural alterations that have recently been linked to disease predisposition. Ultrastructural alterations were even more prominent in homozygous PodR231Q/R2321Qmice eventually resulting in microalbuminuria in aged mice. Consistent with a recently published study, the slit diaphragm length correlated significantly with levels of albuminuria. PodocinR231Q protein levels were decreased in PodR231Q/R231Qmice and human cultured podocytes expressing the variant. Mechanistically, increased proteasomal degradation resulted in a decreased protein stability of podocinR231Qin human cultured podocytes.

Conclusion

Collectively, our data suggest that podocin R231Q may contribute to genetic predisposition in adult patients.