Kidney Week

Abstract: FR-PO0152

Genotype-Phenotype Assessment of Novel NPHS1 Missense Variants Using the HiBiT-Nephrin Evaluation System

Session Information

• Hereditary Glomerular and Tubulointerstitial Kidney Diseases
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1202 Genetic Diseases of the Kidneys: Non-Cystic (Complex and Non-Cystic Monogenic)

Authors

• Kato, Riko, Kumamoto University Graduate School of Pharmaceutical Sciences Department of Molecular Medicine, Kumamoto, Japan

Riko Kato

• Yamamura, Tomohiko, Kobe University Graduate School of Medicine Department of Pediatrics, Kobe, Hyogo, Japan

Tomohiko Yamamura, MD, PhD

• Tsuhako, Haruki, Kumamoto University Graduate School of Pharmaceutical Sciences Department of Molecular Medicine, Kumamoto, Japan

Haruki Tsuhako, MS

• Suico, Mary Ann, Kumamoto University Graduate School of Pharmaceutical Sciences Department of Molecular Medicine, Kumamoto, Japan

Mary Ann Suico, PhD

• Shuto, Tsuyoshi, Kumamoto University Graduate School of Pharmaceutical Sciences Department of Molecular Medicine, Kumamoto, Japan

Tsuyoshi Shuto, PhD

• Nozu, Kandai, Kobe University Graduate School of Medicine Department of Pediatrics, Kobe, Hyogo, Japan

Kandai Nozu, MD, PhD

• Kai, Hirofumi, Kumamoto University Graduate School of Pharmaceutical Sciences Department of Molecular Medicine, Kumamoto, Japan

Hirofumi Kai, PharmD, PhD

Background

Mutations in NPHS1, encoding nephrin, cause congenital nephrotic syndrome (CNS) by impairing nephrin surface expression and slit diaphragm formation. In addition to severe phenotypes such as congenital nephrotic syndrome of the Finnish type (CNF), NPHS1 variants are also associated with milder conditions including infantile nephrotic syndrome and steroid-resistant nephrotic syndrome (SRNS). While truncating variants are generally highly pathogenic, the effects of missense variants vary according to membrane expression levels, making pathogenicity prediction difficult. We previously developed a nanoluciferase-based HiBiT-Nephrin system for rapid quantitative evaluation of nephrin surface expression. Here, we applied this system to assess genotype-phenotype correlations of newly identified NPHS1 variants.

Methods

Using the HiBiT-Nephrin evaluation system, we assessed cell surface expression of newly identified NPHS1 clinical variants. Data were compared with clinical findings, including age at onset and disease severity.

Results

Patients carrying the novel NPHS1 variants exhibited a broad clinical spectrum, including CNF, infantile nephrotic syndrome, SRNS, and isolated proteinuria. We quantitatively analyzed the cell surface expression of the novel variants using the HiBiT-Nephrin evaluation system. Several variants with reduced membrane expression were associated with earlier onset or more severe phenotypes. A patient homozygous for the R802W variant developed CNS, indicating that R802W is a pathogenic variant. Consistently, the R802W variant showed 26.40% of wild-type membrane expression. In contrast, the W35C variant retained relatively high membrane expression (83.2% of wild type), and was consistent with a milder clinical phenotype, despite the coexistence of a truncating variant (2515del) identified in this patient with SRNS. These data indicated that the HiBiT-Nephrin assay may provide a useful functional correlate between NPHS1genotype and clinical phenotype.

Conclusion

By quantifying the membrane expression of novel NPHS1 missense variants, we showed a correlation between membrane expression level and clinical phenotypes. These findings suggest that the HiBiT-Nephrin evaluation system may be useful for predicting disease severity in patients with nephrotic syndrome.

Funding

• Government Support – Non-U.S.