ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: FR-PO1006

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

Session Information

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
  • Widmeier, Eugen, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
  • Arif, Ehtesham, Medical University of South Carolina, Charleston, South Carolina, United States
  • Daga, Ankana, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
  • Helmstädter, Martin, University of Freiburg, Freiburg, Germany
  • Srivastava, Pankaj, Medical University of South Carolina, Charleston, South Carolina, United States
  • Kwon, Kenneth, Medical University of South Carolina, Charleston, South Carolina, United States
  • Shril, Shirlee, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
  • Bergmann, Carsten, University Medical Center Freiburg, Breisacher Straße, Freiburg im Breisgau, Germany
  • Huber, Tobias B., University Medical Center Freiburg, Breisacher Straße, Freiburg im Breisgau, Germany
  • Hildebrandt, Friedhelm, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, United States
  • Nihalani, Deepak, Medical University of South Carolina, Charleston, South Carolina, United States
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