Abstract: SA-PO575
NOS1AP Mutations Cause Steroid-Resistant Nephrotic Syndrome
Session Information
- Noncystic Mendelian Diseases
November 04, 2017 | Location: Hall H, Morial Convention Center
Abstract Time: 10:00 AM - 10:00 AM
Category: Genetic Diseases of the Kidney
- 802 Non-Cystic Mendelian Diseases
Authors
- Majmundar, Amar J., Boston Children's Hospital, Boston, Massachusetts, United States
- Braun, Daniela A., Boston Children's Hospital, Boston, Massachusetts, United States
- Widmeier, Eugen, Boston Children's Hospital, Boston, Massachusetts, United States
- Shril, Shirlee, Boston Children's Hospital, Boston, Massachusetts, United States
- Mane, Shrikant M., Yale University, New Haven, Connecticut, United States
- Soliman, Neveen, Cairo University, Cairo, Egypt
- Aufricht, Christoph, Medical University of Vienna, Vienna, Austria
- Hildebrandt, Friedhelm, Boston Children's Hospital, Boston, Massachusetts, United States
Background
Steroid resistant nephrotic syndrome (SRNS) is the second leading cause of chronic kidney disease in the first three decades of life. Mutations in >39 genes provide a monogenic cause in 29.5% of SRNS cases (Sadowski JASN 26:1279, 2015) and have defined patho-mechanisms (Lovric NDT 31:1802, 2016).
Methods
We performed whole exome sequencing (WES). Live cell imaging was performed following wild-type and mutated cDNA construct expression in immortalized human podocytes.
Results
By WES, we identified homozygous recessive mutations in 2 unrelated individuals with SRNS in the gene NOS1AP (c.428G>A; p.C143Y in subject A1018 and c.345-3T>G; p.I116Afs*4 in subject A5016). NOS1AP encodes an adaptor protein that interacts with nitric oxide synthase (NOS) and with NOS effectors through its phospho-tyrosine binding domain (PTB) (Fang Neuron 28:183, 2000). The C143 residue within the PTB is conserved through invertebrate orthologues and in 85% of 101 human PTB sequences. The p.C143Y change registered strong SIFT and PolyPhen-2 scores. The c.345-3T>G coding change is predicted to reduce splicing of the acceptor site of intron 4. Skipping of adjacent exon 5 results in the truncating coding change p.I116Afs*4. Neither mutation is observed in the ExAC Exome Database. NOS1AP is expressed in podocytes but not endothelial or mesangial cells of rat kidney glomeruli. Transfection of wild-type NOS1AP induced filopodia in 58% of immortalized human podocytes versus only 1% of mock GFP transfected cells. Podocytes transfected with mutated NOS1AP p.C143Y and NOS1AP p.I116Afs*4, which we detected in the SRNS subjects, lacked filopodia formation, demonstrating loss of NOS1AP function.
Conclusion
We identified mutations in NOS1AP in 2 unrelated families with SRNS, revealing a novel monogenic cause of glomerular disease. These findings highlight a new pathogenic mechanism related to nitric oxide signaling and a potential therapeutic target for nephrotic syndrome.
Funding
- NIDDK Support