Kidney Week

Abstract: FR-PO1006

Recessive Mutations in the Kirrel Gene in Human Nephrotic Syndrome (NS)

Session Information

• Genetic Diseases of the Kidneys: Non-Cystic - II
  October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidney

• 1002 Genetic Diseases of the Kidney: Non-Cystic

Authors

• Solanki, Ashish K., Medical University of South Carolina, Charleston, South Carolina, United States

Ashish K. Solanki,

• Widmeier, Eugen, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States

Eugen Widmeier,

• Arif, Ehtesham, Medical University of South Carolina, Charleston, South Carolina, United States

Ehtesham Arif,

• Daga, Ankana, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States

Ankana Daga,

• Helmstädter, Martin, University of Freiburg, Freiburg, Germany

Martin Helmstädter,

• Srivastava, Pankaj, Medical University of South Carolina, Charleston, South Carolina, United States

Pankaj Srivastava,

• Kwon, Kenneth, Medical University of South Carolina, Charleston, South Carolina, United States

Kenneth Kwon,

• Shril, Shirlee, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States

Shirlee Shril,

• Bergmann, Carsten, University Medical Center Freiburg, Breisacher Straße, Freiburg im Breisgau, Germany

Carsten Bergmann,

• Huber, Tobias B., University Medical Center Freiburg, Breisacher Straße, Freiburg im Breisgau, Germany

Tobias B. Huber,

• Hildebrandt, Friedhelm, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States

Friedhelm Hildebrandt,

• Nihalani, Deepak, Medical University of South Carolina, Charleston, South Carolina, United States

Deepak Nihalani,

Background

Steroid-resistant nephrotic syndrome inevitably progresses to end-stage renal disease within the first three decades of life requiring dialysis or transplantation for survival. Podocyte proteins Neph1 and Nephrin form a critical structural framework of a functional glomerular filtration barrier. While many mutations in the Nephrin gene have been described, there are no reports of human mutations in the Neph1/Kirrel gene associated with the NS.

Methods

To identify novel monogenic causes of NS, we performed whole exome sequencing. To investigate the molecular mechanisms of a newly identified monogenic cause of NS in vitro we generated stable podocyte cell lines expressing human wild-type and mutant Neph1. IF studies were performed for localization defects for Neph1 mutants. Neph1 knockdown in podocytes using specific shRNA was performed to evaluate the effect of Neph1 depletion on cell proliferation and migration.

Results

Using next-generation sequencing, we identified two homozygous recessive missense mutations in two unrelated families with NS, which were in a region of high evolutionary conservation (Danio rerio). Immunofluorescence studies revealed that unlike WT Neph1, both Neph1 mutants failed to localize at the podocyte cell membrane (Fig 1). Additionally, we find an increased accumulation of these proteins in endosomes suggesting defective localization, which may contribute to the disease phenotype. Further, these mutant cell lines formed impaired tight junctions as evaluated by the permeability assay using labeled BSA.

Conclusion

This is the first report showing mutations in the Kirrel gene in FSGS patients.

IF showing reduced localization of mutant Neph1 proteins at the podocyte cell membrane

Funding

• NIDDK Support