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-PO1017

A Novel Heterozygous Missense Mutation of Wilms’ Tumor 1 May Cause FSGS Through Dysregulated Expression of ARHGAP24

Session Information

Category: Genetic Diseases of the Kidney

  • 1002 Genetic Diseases of the Kidney: Non-Cystic

Authors

  • Hall, Gentzon, Duke University Medical Center, Durham, North Carolina, United States
  • Sampson, Matt G., University of Michigan, Ann Arbor, Michigan, United States
  • Lane, Brandon M., Duke University, Durham, North Carolina, United States
  • Gregory, Olivia G., Duke University Medical Center, Durham, North Carolina, United States
  • Kovalik, Maria Eugenia, Duke University, Durham, North Carolina, United States
  • Wu, Guanghong, Duke university, Durham, North Carolina, United States
  • Chryst-Stangl, Megan, Duke Molecular Physiology Institute, Durham, North Carolina, United States
  • Wang, Liming, Duke University Medical Center, Durham, North Carolina, United States
  • Spurney, Robert F., Duke University Medical Center, Durham, North Carolina, United States
  • Gbadegesin, Rasheed A., Duke University Medical Center, Durham, North Carolina, United States
Background

Mutations of the transcriptional regulator Wilms’ Tumor 1 are most commonly associated with syndromic disease but some mutations have been shown to cause renal-limited disease. We previously reported a novel heterozygous missense mutation (Exon 9; p.R458Q) of Wilms’ Tumor 1 that caused non-syndromic autosomal dominant FSGS in two Northern European kindreds. We now report a second novel WT1 mutation (Exon 8; p.R443G) as a cause of non-syndromic autosomal dominant FSGS in a 3-generation kindred from North-Central India.

Methods

Direct sequencing, lentivirus-mediated WT1 expression, immunoblot, immunofluorescence imaging, electrophoretic mobility shift assay (EMSA) and apoptosis assays.

Results

A novel heterozygous missense mutation of WT1 (Exon 8; p.R443G) was identified by direct sequencing of the proband and an affected cousin in a North-Central Indian kindred with non-syndromic FSGS. An autosomal dominant pattern of inheritance was suggested by male-to-male transmission across three generations of the family. Substitution of the highly conserved arginine residue at position 443 was considered damaging by in-silico prediction. The R443G mutation impaired DNA-binding by EMSA and distorted the secondary structure of the transcription factor DNA-binding domain by in-silico modeling. WT1 was previously identified as a potential regulator of ARHGAP24; a known FSGS gene that regulates podocyte cytoskeletal dynamics and survival through modulation of Rac1 activity. ARHGAP24 protein expression was significantly upregulated in WT1R443G podocytes (p=0.003; n=3) relative to WT1WT podocytes. Consistent with the increase in ARHGAP24 expression, WT1R443G podocytes exhibited decreased motility (p=0.01; n=3) and increased apoptosis (p=0.04; n=5) accompanied by a significant decrease in STAT3 phosphorylation at Ser727 (p=0.02; n=3); a Rac1-mediated prosurvival post-translational modification. These findings suggest that WT1 functions as an inhibitor of ARHGAP24 expression and the R443G mutation impairs this inhibitory effect.

Conclusion

The novel WT1R443G mutation causes non-syndromic FSGS. The mutation induces an upregulation of ARHGAP24 expression and increases podocyte apoptosis probably through decreased Rac1-mediated prosurvival signaling.

Funding

  • NIDDK Support