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Yang H, He L, Gong H, Wan C, Ding J, Liao P, Wang X. Identification of novel pathogenic variants of CUBN in patients with isolated proteinuria. Mol Genet Genomic Med 2024; 12:e2353. [PMID: 38488435 PMCID: PMC10941600 DOI: 10.1002/mgg3.2353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2023] [Revised: 11/29/2023] [Accepted: 12/11/2023] [Indexed: 03/18/2024] Open
Abstract
BACKGROUND Although proteinuria is long recognized as an independent risk factor for progressive chronic kidney diseases, not all forms of proteinuria are detrimental to kidney function, one of which is isolated proteinuria caused by cubilin (CUBN)-specific mutations. CUBN encodes an endocytic receptor, initially found to be responsible for the Imerslund-Gräsbeck syndrome (IGS; OMIM #261100) characterized by a combined phenotype of megaloblastic anemia and proteinuria. METHODS After analyzing their clinical and pathological characterizations, next-generation sequencing for renal disease genes or whole-exome sequencing (WES) was performed on four patients with non-progressive isolated proteinuria. CUBN biallelic pathogenic variants were identified and further analyzed by cDNA-PCR sequencing, immunohistochemistry, minigene assay, and multiple in silico prediction tools, including 3D protein modeling. RESULTS Here, we present four patients with isolated proteinuria caused by CUBN C-terminal biallelic pathogenic variants, all of which showed no typical IGS symptoms, such as anemia and vitamin B12 deficiency. Their urine protein levels fluctuated between +~++ and estimated glomerular filtration rate (eGFR) were normal or slightly higher. Mild mesangial hypercellularity was found in three children's renal biopsies. A homozygous splice-site variant of CUBN (c.6821+3 (IVS44) A>G) was proven to result in the exon 44 skipping and premature translation termination by cDNA sequencing and immunohistochemistry. Compound heterozygous mutations were identified among the other three children, including another novel splice-site variant (c.10764+1 (IVS66) G>A) causing the retention of first 4 nucleotides in intron 66 by minigene assay, two unreported missense mutations (c.4907G>A (p.R1636Q); c. 9095 A>G (p.Y3032C)), and two reported missense mutations in China (c.8938G>A (p.D2980N); c. 9287T>C (p.L3096P)), locating behind the vitamin B12-binding domain, affecting CUB11, CUB16, CUB22, CUB23, and CUB27 domains, respectively. CONCLUSION These results demonstrate that above CUBN mutations may cause non-progressive and isolated proteinuria, expanding the variant spectrum of CUBN and benefiting our understanding of proteinuria and renal function.
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Affiliation(s)
- Huihui Yang
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Lanfen He
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Hongjian Gong
- Clinical Research Center, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Chunhui Wan
- Precision Medical Center, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Juanjuan Ding
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Panli Liao
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
| | - Xiaowen Wang
- Department of Nephrology, Wuhan Children's Hospital (Wuhan Maternal and Child Healthcare Center)Tongji Medical College, Huazhong University of Science & TechnologyWuhanChina
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Satarug S, Vesey DA, Gobe GC, Phelps KR. The pathogenesis of albuminuria in cadmium nephropathy. Curr Res Toxicol 2023; 6:100140. [PMID: 38116328 PMCID: PMC10726218 DOI: 10.1016/j.crtox.2023.100140] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 11/16/2023] [Accepted: 11/30/2023] [Indexed: 12/21/2023] Open
Abstract
Background Urinary cadmium excretion (ECd) rises with renal tissue content of the metal. Whereas glomerulopathies are sometimes associated with massive albuminuria, tubular accumulation of Cd typically causes modest albuminuria. Since β2-microglobulinuria (Eβ2M) is an established marker of proximal tubular dysfunction, we hypothesized that a comparison of albuminuria (Ealb) to Eβ2M in Cd-exposed subjects would provide evidence of similar mishandling of both proteins. Methods To depict excretion rates per functional nephron, ECd, Ealb, and Eβ2M were normalized to creatinine clearance (Ccr), a surrogate for the glomerular filtration rate (GFR). Estimation of GFR itself (eGFR) was accomplished with CKD-EPI formulas (2009). Linear and logistic regression analyses were performed to relate Ealb/Ccr, Eβ2M/Ccr, and eGFR to several independent variables. Simple linear regressions of eGFR, Ealb/Ccr, and Eβ2M/Ccr on ECd/Ccr were examined before and after adjustment of dependent variables for age. All regressions were performed after log-transformation of ratios and standardization of all variables. Increments in Ealb/Ccr and Eβ2M/Ccr and decrements in eGFR were quantified through four quartiles of ECd/Ccr. Results As age or ECd/Ccr rose, Ealb/Ccr and Eβ2M/Ccr also rose, and eGFR fell. In linear regressions, slopes relating Ealb/Ccr and Eβ2M/Ccr to ECd/Ccr were similar. After adjustment of dependent variables for age, coefficients of determination (R2) for all regressions rose by a multiple, and slopes approached unity. Ealb/Ccr and Eβ2M/Ccr were similarly associated with each other. Mean Ealb/Ccr and Eβ2M/Ccr rose and mean eGFR fell in stepwise fashion through quartiles of ECd/Ccr. Whereas Eβ2M/Ccr did not vary with blood pressure, Ealb/Ccr rose in association with hypertension in two of the four quartiles. Conclusions Our data indicate that Cd in renal tissue affected tubular reabsorption of albumin and β2M similarly in a large cohort of exposed subjects. The results suggest that Cd reduced receptor-mediated endocytosis and subsequent lysosomal degradation of each protein by a shared mechanism.
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Affiliation(s)
- Soisungwan Satarug
- Centre for Kidney Disease Research, Translational Research Institute, Brisbane, Australia
| | - David A. Vesey
- Centre for Kidney Disease Research, Translational Research Institute, Brisbane, Australia
- Department of Kidney and Transplant Services, Princess Alexandra Hospital, Brisbane, Australia
| | - Glenda C. Gobe
- Centre for Kidney Disease Research, Translational Research Institute, Brisbane, Australia
- School of Biomedical Sciences, The University of Queensland, Brisbane, Australia
- NHMRC Centre of Research Excellence for CKD QLD, UQ Health Sciences, Royal Brisbane and Women’s Hospital, Brisbane, Australia
| | - Kenneth R. Phelps
- Stratton Veterans Affairs Medical Center and Albany Medical College, Albany, NY, USA
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Shi V, Stein Q, Clark D, Punj S, Kremsdorf R, Faizan M. Isolated benign persistent proteinuria with novel association of CUBN (cubilin) variants. Clin Case Rep 2023; 11:e7502. [PMID: 37312928 PMCID: PMC10258721 DOI: 10.1002/ccr3.7502] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 05/18/2023] [Accepted: 05/29/2023] [Indexed: 06/15/2023] Open
Abstract
We present two siblings with persistent proteinuria and normal kidney function, each carrying the same compound heterozygous variants in the CUBN gene. The CUBN-related phenotype appears to be dependent upon both variant type and the domain site within the gene. Knowledge of CUBN status may allow for avoidance of invasive testing.
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Affiliation(s)
- Vivian Shi
- Warren Alpert Medical School of Brown UniversityRhode IslandProvidenceUSA
- Department of Medicine, Rhode Island HospitalRhode IslandProvidenceUSA
- Department of Pediatrics, Hasbro Children’s HospitalRhode IslandProvidenceUSA
| | | | | | | | - Robin Kremsdorf
- Warren Alpert Medical School of Brown UniversityRhode IslandProvidenceUSA
- Department of Medicine, Rhode Island HospitalRhode IslandProvidenceUSA
- Department of Pediatrics, Hasbro Children’s HospitalRhode IslandProvidenceUSA
| | - Mohammed Faizan
- Warren Alpert Medical School of Brown UniversityRhode IslandProvidenceUSA
- Department of Medicine, Rhode Island HospitalRhode IslandProvidenceUSA
- Department of Pediatrics, Hasbro Children’s HospitalRhode IslandProvidenceUSA
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Uglebjerg N, Ahmadizar F, Aly DM, Cañadas-Garre M, Hill C, Naber A, Oddsson A, Singh SS, Smyth L, Trégouët DA, Chaker L, Ghanbari M, Steinthorsdottir V, Ahlqvist E, Hadjadj S, Van Hoek M, Kavousi M, McKnight AJ, Sijbrands EJ, Stefansson K, Simons M, Rossing P, Ahluwalia TS. Four missense genetic variants in CUBN are associated with higher levels of eGFR in non-diabetes but not in diabetes mellitus or its subtypes: A genetic association study in Europeans. Front Endocrinol (Lausanne) 2023; 14:1081741. [PMID: 36926036 PMCID: PMC10011651 DOI: 10.3389/fendo.2023.1081741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 02/07/2023] [Indexed: 03/08/2023] Open
Abstract
AIM Rare genetic variants in the CUBN gene encoding the main albumin-transporter in the proximal tubule of the kidneys have previously been associated with microalbuminuria and higher urine albumin levels, also in diabetes. Sequencing studies in isolated proteinuria suggest that these variants might not affect kidney function, despite proteinuria. However, the relation of these CUBN missense variants to the estimated glomerular filtration rate (eGFR) is largely unexplored. We hereby broadly examine the associations between four CUBN missense variants and eGFRcreatinine in Europeans with Type 1 (T1D) and Type 2 Diabetes (T2D). Furthermore, we sought to deepen our understanding of these variants in a range of single- and aggregate- variant analyses of other kidney-related traits in individuals with and without diabetes mellitus. METHODS We carried out a genetic association-based linear regression analysis between four CUBN missense variants (rs141640975, rs144360241, rs45551835, rs1801239) and eGFRcreatinine (ml/min/1.73 m2, CKD-EPIcreatinine(2012), natural log-transformed) in populations with T1D (n ~ 3,588) or T2D (n ~ 31,155) from multiple European studies and in individuals without diabetes from UK Biobank (UKBB, n ~ 370,061) with replication in deCODE (n = 127,090). Summary results of the diabetes-group were meta-analyzed using the fixed-effect inverse-variance method. RESULTS Albeit we did not observe associations between eGFRcreatinine and CUBN in the diabetes-group, we found significant positive associations between the minor alleles of all four variants and eGFRcreatinine in the UKBB individuals without diabetes with rs141640975 being the strongest (Effect=0.02, PeGFR_creatinine=2.2 × 10-9). We replicated the findings for rs141640975 in the Icelandic non-diabetes population (Effect=0.026, PeGFR_creatinine=7.7 × 10-4). For rs141640975, the eGFRcreatinine-association showed significant interaction with albuminuria levels (normo-, micro-, and macroalbuminuria; p = 0.03). An aggregated genetic risk score (GRS) was associated with higher urine albumin levels and eGFRcreatinine. The rs141640975 variant was also associated with higher levels of eGFRcreatinine-cystatin C (ml/min/1.73 m2, CKD-EPI2021, natural log-transformed) and lower circulating cystatin C levels. CONCLUSIONS The positive associations between the four CUBN missense variants and eGFR in a large population without diabetes suggests a pleiotropic role of CUBN as a novel eGFR-locus in addition to it being a known albuminuria-locus. Additional associations with diverse renal function measures (lower cystatin C and higher eGFRcreatinine-cystatin C levels) and a CUBN-focused GRS further suggests an important role of CUBN in the future personalization of chronic kidney disease management in people without diabetes.
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Affiliation(s)
- Nicoline Uglebjerg
- Complications Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
| | - Fariba Ahmadizar
- Department of Epidemiology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
- Department of Data Science & Biostatistics, Julius Global Health, University Medical Center Utrecht, Utrecht, Netherlands
| | - Dina M. Aly
- Department of Clinical Sciences, Lund University, Malmö, Sweden
| | - Marisa Cañadas-Garre
- Centre for Public Health, Queen’s University Belfast, Belfast, United Kingdom
- GENYO Centre for Genomics and Oncological Research, Pfizer-University of Granada-Andalusian Regional Government, Granada, Spain
- Instituto de Investigación Biosanitaria de Granada (ibs.GRANADA), Granada, Spain
| | - Claire Hill
- Centre for Public Health, Queen’s University Belfast, Belfast, United Kingdom
| | - Annemieke Naber
- Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | | | - Sunny S. Singh
- Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Laura Smyth
- Centre for Public Health, Queen’s University Belfast, Belfast, United Kingdom
| | - David-Alexandre Trégouët
- University of Bordeaux, Institut National de la Santé et de la Recherche Médicale (INSERM), Bordeaux Population Health Research Center, Bordeaux, France
| | - Layal Chaker
- Department of Epidemiology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
- Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Mohsen Ghanbari
- Department of Epidemiology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | | | - Emma Ahlqvist
- Department of Clinical Sciences, Lund University, Malmö, Sweden
| | - Samy Hadjadj
- Nantes Université, Centre Hospitalier Universitaire Nantes, Centre National de la Recherche Scientifique, INSERM, l’institut du thorax, Nantes, France
| | - Mandy Van Hoek
- Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Maryam Kavousi
- Department of Epidemiology, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Amy Jayne McKnight
- Centre for Public Health, Queen’s University Belfast, Belfast, United Kingdom
| | - Eric J. Sijbrands
- Department of Internal Medicine, Erasmus Medical Center, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Kari Stefansson
- deCODE Genetics, Amgen, Inc., Reykjavik, Iceland
- Faculty of Medicine, School of Health Sciences, University of Iceland, Reykjavik, Iceland
| | - Matias Simons
- Institute of Human Genetics, University Hospital Heidelberg, Heidelberg, Germany
| | - Peter Rossing
- Complications Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
- Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
| | - Tarunveer S. Ahluwalia
- Complications Research, Steno Diabetes Center Copenhagen, Herlev, Denmark
- The Bioinformatics Center, Department of Biology, University of Copenhagen, Copenhagen, Denmark
- *Correspondence: Tarunveer S. Ahluwalia,
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