Kidney Week

Abstract: SA-PO622

Deletion of Gapvd1 Sensitizes Murine Podocytes to Adriamycin-Induced Injury

Session Information

• Genetic Kidney Diseases: Models, Mechanisms, and Therapies
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

• Gerstner, Lea, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Lea Gerstner, PhD

• Spitz, Dominik, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Dominik Spitz

• Milosavljevic, Julian, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Julian Milosavljevic, MD

• Kampf, Lina Luise, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Lina Luise Kampf

• Brettel, Marc, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Marc Brettel

• Lempicki, Camille, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Camille Lempicki

• Helmstädter, Martin, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Martin Helmstädter

• Bechtel-Walz, Wibke, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Wibke Bechtel-Walz, DrMed

• Walz, Gerd, Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Gerd Walz, MD

• Hermle, Tobias F., Renal Division, Department of Medicine, Faculty of Medicine and Medical Center - University of Freiburg, Freiburg, Germany

Tobias F. Hermle, MD

Background

DNA variants in GAPVD1, an activator of endosomal protein Rab5, are a monogenic cause of nephrotic syndrome. The encoded protein interacts with nephrin and previous studies in podocyte-like nephrocytes in Drosophila suggested a crucial function for slit diaphragm integrity. However, the role of this gene remained unexplored in mammalian animal models.

Methods

To generate a conditional knockout, we established a Gapvd1 allele with loxP sites flanking exon 4. Gapvd1^fl/fl mice were crossed with Nphs2-Cre for podocyte-specific deletion and Six2-Cre for deletion in nephron progenitor cells. To apply toxicity stress, sixteen week old Nphs2-Cre; Gapvd1^fl/fl mice and control animals (Gapvd1^fl/fl ) were treated with intravenous Adriamycin. For phenotypic characterization, we determined serum creatinine and urinary albumin-to-creatinine ratios (ACR) and further applied histochemistry, immunofluorescence and electron microscopy.

Results

In situ hybridization indicated a successful conditional knockout of Gapvd1. However, unstressed animals using Nphs2-Cre or Six2-Cre for deletion of Gapvd1 revealed no overt phenotype including changes in glomerular architecture, renal function and urinary ACR. In contrast, Adriamycin-injected Nphs2-Cre, Gapvd1^fl/fl mice presented with elevated proteinuria compared to the control group. Periodic acid-Schiff staining of kidney sections indicated focal segmental glomerulosclerosis in stressed knockout animals, which further exhibited significantly less WT1-positive podocytes per glomerulus in immunofluorescence. Analysis of glomeruli with scanning electron microscopy revealed shortened and partially fused foot processes and transmission electron microscopy confirmed foot process effacement.

Conclusion

Gapvd1 seems dispensable for podocyte homeostasis in unstressed mice, likely due to compensation by another Rab5-regulating protein. However, loss of Gapvd1 sensitized animals to Adriamycin-induced podocyte injury resulting in podocyte loss and proteinuria.

Funding

• Government Support – Non-U.S.