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Aklilu AM, Gulati A, Kolber KJ, Yang H, Harris PC, Dahl NK. The VUS Challenge in Cystic Kidney Disease: A Case-Based Review. KIDNEY360 2024; 5:152-159. [PMID: 37962562 PMCID: PMC10833605 DOI: 10.34067/kid.0000000000000298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 10/26/2023] [Indexed: 11/15/2023]
Abstract
Genetic testing in nephrology is becoming increasingly important to diagnose patients and to provide appropriate care. This is especially true for autosomal dominant polycystic kidney disease (ADPKD) because this is a common cause of kidney failure and genetically complex. In addition to the major genes, PKD1 and PKD2 , there are at least six minor loci, and phenotypic, and in some cases, genetic overlap with other cystic disorders. Targeted next-generation sequencing, a low-cost, high-throughput technique, has made routine genetic testing viable in nephrology clinics. Appropriate pre- and post-testing genetic counseling is essential to the testing process. Carefully assessing variants is also critical, with the genetic report classifying variants in accordance with American College of Medical Genetics and Genomics guidelines. However, variant of uncertain significance (VUSs) may pose a significant challenge for the ordering clinician. In ADPKD, and particularly within PKD1 , there is high allelic heterogeneity; no single variant is present in more than 2% of families. The Mayo/Polycystic Kidney Disease Foundation variant database, a research tool, is the best current database of PKD1 and PKD2 variants containing over 2300 variants identified in individuals with polycystic kidney disease, but novel variants are often identified. In patients with a high pretest probability of ADPKD on the basis of clinical criteria, but no finding of a pathogenic (P) or likely pathogenic (LP) variant in a cystic kidney gene, additional evaluation of cystic gene VUS can be helpful. In this case-based review, we propose an algorithm for the assessment of such variants in a clinical setting and show how some can be reassigned to a diagnostic grouping. When assessing the relevance of a VUS, we consider both patient/family-specific and allele-related factors using population and variant databases and available prediction tools, as well as genetic expertise. This analysis plus further family studies can aid in making a genetic diagnosis.
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Affiliation(s)
- Abinet M. Aklilu
- Section of Nephrology, Yale University School of Medicine, New Haven, Connecticut
| | | | - Kayla J. Kolber
- Center for Individualized Medicine, Mayo Clinic, Rochester, Minnesota
| | - Hana Yang
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Peter C. Harris
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
| | - Neera K. Dahl
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, Minnesota
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A Potential Therapy Using Antisense Oligonucleotides to Treat Autosomal Recessive Polycystic Kidney Disease. J Clin Med 2023; 12:jcm12041428. [PMID: 36835961 PMCID: PMC9966971 DOI: 10.3390/jcm12041428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Revised: 02/01/2023] [Accepted: 02/08/2023] [Indexed: 02/16/2023] Open
Abstract
(1) Background: Autosomal recessive polycystic kidney disease (ARPKD) is a rare ciliopathy characterized by progressively enlarged kidneys with fusiform dilatation of the collecting ducts. Loss-of-function mutations in the PKHD1 gene, which encodes fibrocystin/polyductin, cause ARPKD; however, an efficient treatment method and drug for ARPKD have yet to be found. Antisense oligonucleotides (ASOs) are short special oligonucleotides which function to regulate gene expression and alter mRNA splicing. Several ASOs have been approved by the FDA for the treatment of genetic disorders, and many are progressing at present. We designed ASOs to verify whether ASOs mediate the correction of splicing further to treat ARPKD arising from splicing defects and explored them as a potential treatment option. (2) Methods: We screened 38 children with polycystic kidney disease for gene detection using whole-exome sequencing (WES) and targeted next-generation sequencing. Their clinical information was investigated and followed up. The PKHD1 variants were summarized and analyzed, and association analysis was carried out to analyze the relationship between genotype and phenotype. Various bioinformatics tools were used to predict pathogenicity. Hybrid minigene analysis was performed as part of the functional splicing analysis. Moreover, the de novo protein synthesis inhibitor cycloheximide was selected to verify the degraded pathway of abnormal pre-mRNAs. ASOs were designed to rescue aberrant splicing, and this was verified. (3) Results: Of the 11 patients with PKHD1 variants, all of them exhibited variable levels of complications of the liver and kidneys. We found that patients with truncating variants and variants in certain regions had a more severe phenotype. Two splicing variants of the PKHD1 genotypes were studied via the hybrid minigene assay: variants c.2141-3T>C and c.11174+5G>A. These cause aberrant splicing, and their strong pathogenicity was confirmed. We demonstrated that the abnormal pre-mRNAs produced from the variants escaped from the NMD pathway with the use of the de novo protein synthesis inhibitor cycloheximide. Moreover, we found that the splicing defects were rescued by using ASOs, which efficiently induced the exclusion of pseudoexons. (4) Conclusion: Patients with truncating variants and variants in certain regions had a more severe phenotype. ASOs are a potential drug for treating ARPKD patients harboring splicing mutations of the PKHD1 gene by correcting the splicing defects and increasing the expression of the normal PKHD1 gene.
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Genetics, pathobiology and therapeutic opportunities of polycystic liver disease. Nat Rev Gastroenterol Hepatol 2022; 19:585-604. [PMID: 35562534 DOI: 10.1038/s41575-022-00617-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/07/2022] [Indexed: 12/12/2022]
Abstract
Polycystic liver diseases (PLDs) are inherited genetic disorders characterized by progressive development of intrahepatic, fluid-filled biliary cysts (more than ten), which constitute the main cause of morbidity and markedly affect the quality of life. Liver cysts arise in patients with autosomal dominant PLD (ADPLD) or in co-occurrence with renal cysts in patients with autosomal dominant or autosomal recessive polycystic kidney disease (ADPKD and ARPKD, respectively). Hepatic cystogenesis is a heterogeneous process, with several risk factors increasing the odds of developing larger cysts. Depending on the causative gene, PLDs can arise exclusively in the liver or in parallel with renal cysts. Current therapeutic strategies, mainly based on surgical procedures and/or chronic administration of somatostatin analogues, show modest benefits, with liver transplantation as the only potentially curative option. Increasing research has shed light on the genetic landscape of PLDs and consequent cholangiocyte abnormalities, which can pave the way for discovering new targets for therapy and the design of novel potential treatments for patients. Herein, we provide a critical and comprehensive overview of the latest advances in the field of PLDs, mainly focusing on genetics, pathobiology, risk factors and next-generation therapeutic strategies, highlighting future directions in basic, translational and clinical research.
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Fabris L, Milani C, Fiorotto R, Mariotti V, Kaffe E, Seller B, Sonzogni A, Strazzabosco M, Cadamuro M. Dysregulation of the Scribble/YAP/β-catenin axis sustains the fibroinflammatory response in a PKHD1 -/- mouse model of congenital hepatic fibrosis. FASEB J 2022; 36:e22364. [PMID: 35593740 PMCID: PMC9150862 DOI: 10.1096/fj.202101924r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 04/25/2022] [Accepted: 05/10/2022] [Indexed: 11/11/2022]
Abstract
Congenital hepatic fibrosis (CHF), a genetic cholangiopathy characterized by fibropolycystic changes in the biliary tree, is caused by mutations in the PKHD1 gene, leading to defective fibrocystin (FPC), changes in planar cell polarity (PCP) and increased β-catenin-dependent chemokine secretion. In this study, we aimed at understanding the role of Scribble (a protein involved in PCP), Yes-associated protein (YAP), and β-catenin in the regulation of the fibroinflammatory phenotype of FPC-defective cholangiocytes. Immunohistochemistry showed that compared with wild type (WT) mice, in FPC-defective (Pkhd1del4/del4 ) mice nuclear expression of YAP/TAZ in cystic cholangiocytes, significantly increased and correlated with connective tissue growth factor (CTGF) expression and pericystic fibrosis, while Scribble expression on biliary cyst cells was markedly decreased. Cholangiocytes isolated from WT mice showed intense Scribble immunoreactivity at the membrane, but minimal nuclear expression of YAP, which conversely increased, together with CTGF, after small interfering RNA (siRNA) silencing of Scribble. In FPC-defective cholangiocytes, inhibition of YAP nuclear import reduced β-catenin nuclear expression, and CTGF, integrin β6, CXCL1, and CXCL10 mRNA levels, whereas inhibition of β-catenin signaling did not affect nuclear translocation of YAP. Notably, siRNA silencing of Scribble and YAP in WT cholangiocytes mimics the fibroinflammatory changes of FPC-defective cholangiocytes. Conditional deletion of β-catenin in Pkhd1del4/del4 mice reduced cyst growth, inflammation and fibrosis, without affecting YAP nuclear expression. In conclusion, the defective anchor of Scribble to the membrane facilitates the nuclear translocation of YAP and β-catenin with gain of a fibroinflammatory phenotype. The Scribble/YAP/β-catenin axis is a critical factor in the sequence of events linking the genetic defect to fibrocystic trait of cholangiocytes in CHF.
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Affiliation(s)
- Luca Fabris
- Department of Molecular Medicine (DMM), University of Padova, Padova, Italy
- International Center for Digestive Health (ICDH), University of Milan-Bicocca, Milan, Italy
- Liver Center, Department of Internal Medicine, Yale University, New Haven (CT), US
| | - Chiara Milani
- School of Medicine and Surgery, University of Milan-Bicocca, Milan, Italy
| | - Romina Fiorotto
- Liver Center, Department of Internal Medicine, Yale University, New Haven (CT), US
| | - Valeria Mariotti
- Department of Molecular Medicine (DMM), University of Padova, Padova, Italy
- Liver Center, Department of Internal Medicine, Yale University, New Haven (CT), US
| | - Eleanna Kaffe
- Liver Center, Department of Internal Medicine, Yale University, New Haven (CT), US
| | - Barbara Seller
- School of Medicine and Surgery, University of Milan-Bicocca, Milan, Italy
| | - Aurelio Sonzogni
- Department of Pathology, ASST Papa Giovanni XXIII Hospital, Bergamo, Italy
| | - Mario Strazzabosco
- Liver Center, Department of Internal Medicine, Yale University, New Haven (CT), US
- Corresponding authors: Mario Strazzabosco, MD, PhD, Department of Internal Medicine, Yale University School of Medicine, Cedar Street 333 Room LMP1080, New Haven, CT 06517, USA. Phone: +1‐203‐785‐5110, , Massimiliano Cadamuro, PhD, Department of Molecular Medicine, University of Padova, Gabelli Street 63, Padova, 35121, Italy. Phone: +39-049-827-6113,
| | - Massimiliano Cadamuro
- Department of Molecular Medicine (DMM), University of Padova, Padova, Italy
- International Center for Digestive Health (ICDH), University of Milan-Bicocca, Milan, Italy
- Corresponding authors: Mario Strazzabosco, MD, PhD, Department of Internal Medicine, Yale University School of Medicine, Cedar Street 333 Room LMP1080, New Haven, CT 06517, USA. Phone: +1‐203‐785‐5110, , Massimiliano Cadamuro, PhD, Department of Molecular Medicine, University of Padova, Gabelli Street 63, Padova, 35121, Italy. Phone: +39-049-827-6113,
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Sudarikova A, Vasileva V, Sultanova R, Ilatovskaya D. Recent advances in understanding ion transport mechanisms in polycystic kidney disease. Clin Sci (Lond) 2021; 135:2521-2540. [PMID: 34751394 PMCID: PMC8589009 DOI: 10.1042/cs20210370] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 10/15/2021] [Accepted: 10/26/2021] [Indexed: 12/18/2022]
Abstract
This review focuses on the most recent advances in the understanding of the electrolyte transport-related mechanisms important for the development of severe inherited renal disorders, autosomal dominant (AD) and recessive (AR) forms of polycystic kidney disease (PKD). We provide here a basic overview of the origins and clinical aspects of ARPKD and ADPKD and discuss the implications of electrolyte transport in cystogenesis. Special attention is devoted to intracellular calcium handling by the cystic cells, with a focus on polycystins and fibrocystin, as well as other calcium level regulators, such as transient receptor potential vanilloid type 4 (TRPV4) channels, ciliary machinery, and purinergic receptor remodeling. Sodium transport is reviewed with a focus on the epithelial sodium channel (ENaC), and the role of chloride-dependent fluid secretion in cystic fluid accumulation is discussed. In addition, we highlight the emerging promising concepts in the field, such as potassium transport, and suggest some new avenues for research related to electrolyte handling.
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Affiliation(s)
| | | | - Regina F. Sultanova
- Saint-Petersburg State Chemical Pharmaceutical University, St. Petersburg, Russia
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de Fallois J, Schönauer R, Münch J, Nagel M, Popp B, Halbritter J. Challenging Disease Ontology by Instances of Atypical PKHD1 and PKD1 Genetics. Front Genet 2021; 12:682565. [PMID: 34249099 PMCID: PMC8267867 DOI: 10.3389/fgene.2021.682565] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 05/05/2021] [Indexed: 12/03/2022] Open
Abstract
Background Autosomal polycystic kidney disease is distinguished into dominant (ADPKD) and recessive (ARPKD) inheritance usually caused by either monoallelic (PKD1/PKD2) or biallelic (PKHD1) germline variation. Clinical presentations are genotype-dependent ranging from fetal demise to mild chronic kidney disease (CKD) in adults. Additionally, exemptions from dominant and recessive inheritance have been reported in both disorders resulting in respective phenocopies. Here, we comparatively report three young adults with microcystic-hyperechogenic kidney morphology based on unexpected genetic alterations beyond typical inheritance. Methods Next-generation sequencing (NGS)-based gene panel analysis and multiplex ligation-dependent probe amplification (MLPA) of PKD-associated genes, familial segregation analysis, and reverse phenotyping. Results Three unrelated individuals presented in late adolescence for differential diagnosis of incidental microcystic-hyperechogenic kidneys with preserved kidney and liver function. Upon genetic analysis, we identified a homozygous hypomorphic PKHD1 missense variant causing pseudodominant inheritance in a family, a large monoallelic PKDH1-deletion with atypical transmission, and biallelic PKD1 missense hypomorphs with recessive inheritance. Conclusion By this report, we illustrate clinical presentations associated with atypical PKD-gene alterations beyond traditional modes of inheritance. Large monoallelic PKHD1-alterations as well as biallelic hypomorphs of both PKD1 and PKHD1 may lead to mild CKD in the absence of prominent macrocyst formation and functional liver impairment. The long-term renal prognosis throughout life, however, remains undetermined. Increased detection of atypical inheritance challenges our current thinking of disease ontology not only in PKD but also in Mendelian disorders in general.
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Affiliation(s)
- Jonathan de Fallois
- Department of Endocrinology, Nephrology and Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Ria Schönauer
- Department of Endocrinology, Nephrology and Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Johannes Münch
- Department of Endocrinology, Nephrology and Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
| | - Mato Nagel
- Center for Nephrology and Metabolic Disorders, Weißwasser, Germany
| | - Bernt Popp
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany
| | - Jan Halbritter
- Department of Endocrinology, Nephrology and Rheumatology, University of Leipzig Medical Center, Leipzig, Germany
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Boerrigter MM, Bongers EMHF, Lugtenberg D, Nevens F, Drenth JPH. Polycystic liver disease genes: Practical considerations for genetic testing. Eur J Med Genet 2021; 64:104160. [PMID: 33556586 DOI: 10.1016/j.ejmg.2021.104160] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/26/2021] [Accepted: 01/31/2021] [Indexed: 12/15/2022]
Abstract
The development of a polycystic liver is a characteristic of the monogenic disorders: autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive polycystic kidney disease (ARPKD), and autosomal dominant polycystic liver disease (ADPLD). Respectively two and one genes mainly cause ADPKD and ARPKD. In contrast, ADPLD is caused by at least six different genes which combined do not even explain the disease development in over half of the ADPLD population. Genetic testing is mainly performed to confirm the likelihood of developing PKD and if renal therapy is essential. However, pure ADPLD patients are frequently not genetically screened as knowledge about the genotype-phenotype correlation is currently limited. This paper will clarify the essence of genetic testing in ADPLD patients.
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Affiliation(s)
- Melissa M Boerrigter
- Department of Gastroenterology and Hepatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Ernie M H F Bongers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Dorien Lugtenberg
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Frederik Nevens
- Department of Gastroenterology and Hepatology, University Hospitals KU Leuven, Leuven, Belgium
| | - Joost P H Drenth
- Department of Gastroenterology and Hepatology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, the Netherlands.
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