Abstract: SA-PO585
Heterozygous Mutations in Three Novel Candidate Genes, IFT122, WDR19, and WDR35, Cause Autosomal Dominant Polycystic Kidney Disease
Session Information
- Cystic Kidney Diseases: Genetic Causes, Modifiers, and Extrarenal Manifestations
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1201 Genetic Diseases of the Kidneys: Cystic
Authors
- Colombo, Dan, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Romero Cruz, Denisse, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Wan, George Wai Chang, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Barreiro-Rosario, Adriana C., Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Dam, Ahona, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Diamond, Alexandra, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Bianchi, Giada, Brigham and Women's Hospital, Boston, Massachusetts, United States
- Oglivy, Christopher S., Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Nasser, Samer S., Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
- Phipps, Elizabeth Ann, Mount Auburn Hospital, Cambridge, Massachusetts, United States
- Mutter, Walter P., Newton-Wellesley Hospital, Newton, Massachusetts, United States
- Robinson, Emily, Brigham and Women's Hospital, Boston, Massachusetts, United States
- Ravi, Katherine Scovner, Brigham and Women's Hospital, Boston, Massachusetts, United States
- Czarnecki, Peter G., Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States
Background
Autosomal-dominant polycystic kidney disease (ADPKD) is one of the most common monogenic diseases in mankind. Despite the identification of two major and various minor causative genes, many cases remain genetically unresolved (“ADPKD-NMD”, “no mutation detected”). We sought to identify novel disease-causing genes by analyzing the genotypes of patients with ADPKD-NMD, and we found numerous variants in IFT122, WDR19 and WDR35. Given the similarity of disease phenotypes and the common biochemical function of the ADPKD gene, IFT140, with the 3 novel candidate genes, we hypothesize that our newly discovered variants are causative in PKD.
Methods
Chart review to identify patients with ADPKD-NMD
Family pedigree genotype-phenotype correlation
CRISPR/Cas9 gene knockout
Lentiviral transduction
Immunofluorescent confocal microscopy
Co-immunoprecipitation/Western blot
Results
Chart analysis revealed 3 families with heterozygous alleles in IFT122 and WDR19, segregating with a clinical PKD phenotype across two generations. We further identified 3 additional IFT122 and 2 WDR35 alleles in singletons, coinciding with clinical PKD. In summary, we found a truncation in WDR19, 2 truncations in WDR35, a truncation and a large in-frame deletion in IFT122, and three missense variants in IFT122.
After CRISPR/Cas9-knockout of the endogenous IFT122, WDR19 and WDR35, and lentiviral add-back transduction, none of the truncation or in-frame deletion alleles rescued the ciliogenesis defect in mIMCD-3 cells. Although the missense variants in IFT122 allowed for cilia formation, ciliary length was significantly reduced compared to the wildtype.
We further show by co-immunoprecipitation and Western blot that the truncation mutations disrupt IFT-A subcomplex formation between IFT140, IFT122, WDR19 and WDR35. IFT122 missense variants exhibit a significantly reduced affinity to their native binding partner, WDR35.
Conclusion
We present the discovery of 3 novel ADPKD genes, IFT122, WDR19 and WDR35. Along with the recently identified ADPKD gene, IFT140, the novel genes represent components of the IFT-A complex that is essential for ciliary handling of PKD1 and PKD2.
Funding
- NIDDK Support