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Thuma TBT, Procopio RA, Jimenez HJ, Gunton KB, Pulido JS. Hypomorphic variants in inherited retinal and ocular diseases: A review of the literature with clinical cases. Surv Ophthalmol 2024; 69:337-348. [PMID: 38036193 DOI: 10.1016/j.survophthal.2023.11.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/17/2023] [Accepted: 11/20/2023] [Indexed: 12/02/2023]
Abstract
Hypomorphic variants decrease, but do not eliminate, gene function via a reduction in the amount of mRNA or protein product produced by a gene or by production of a gene product with reduced function. Many hypomorphic variants have been implicated in inherited retinal diseases (IRDs) and other genetic ocular conditions; however, there is heterogeneity in the use of the term "hypomorphic" in the scientific literature. We searched for all hypomorphic variants reported to cause IRDs and ocular disorders. We also discuss the presence of hypomorphic variants in the patient population of our ocular genetics department over the past decade. We propose that standardized criteria should be adopted for use of the term "hypomorphic" to describe gene variants to improve genetic counseling and patient care outcomes.
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Affiliation(s)
- Tobin B T Thuma
- Department of Pediatric Ophthalmology and Strabismus, Wills Eye Hospital, Philadelphia, PA, USA
| | | | - Hiram J Jimenez
- Vickie and Jack Farber Vision Research Center, Wills Eye Hospital, Philadelphia, PA, USA
| | - Kammi B Gunton
- Department of Pediatric Ophthalmology and Strabismus, Wills Eye Hospital, Philadelphia, PA, USA
| | - Jose S Pulido
- Vickie and Jack Farber Vision Research Center, Wills Eye Hospital, Philadelphia, PA, USA; Retina Service, Wills Eye Hospital, Philadelphia, PA, USA.
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2
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Deitch I, Itskov S, Panneman D, Abu Shtaya A, Saban T, Goldberg Y, Ehrenberg M, Cremers FPM, Roosing S, Ben-Yosef T. Autosomal Recessive Rod-Cone Dystrophy with Mild Extra-Ocular Manifestations Due to a Splice-Affecting Variant in BBS9. Curr Issues Mol Biol 2024; 46:2566-2575. [PMID: 38534779 DOI: 10.3390/cimb46030163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/14/2024] [Accepted: 03/14/2024] [Indexed: 03/28/2024] Open
Abstract
Bardet-Biedl syndrome (BBS), one of the most common forms of syndromic inherited retinal diseases (IRDs), is characterized by the combination of retinal degeneration with additional extra-ocular manifestations, including obesity, intellectual disability, kidney disease, polydactyly and other skeletal abnormalities. We observed an Israeli patient with autosomal recessive apparently non-syndromic rod-cone dystrophy (RCD). Extra-ocular findings were limited to epilepsy and dental problems. Genetic analysis with a single molecule molecular inversion probes-based panel that targets the exons and splice sites of 113 genes associated with retinitis pigmentosa and Leber congenital amaurosis revealed a homozygous rare missense variant in the BBS9 gene (c.263C>T;p.(Ser88Leu)). This variant, which affects a highly conserved amino acid, is also located in the last base of Exon 3, and predicted to be splice-altering. An in vitro minigene splice assay demonstrated that this variant leads to the partial aberrant splicing of Exon 3. Therefore, we suggest that this variant is likely hypomorphic. This is in agreement with the relatively mild phenotype observed in the patient. Hence, the findings in our study expand the phenotypic spectrum associated with BBS9 variants and indicate that variants in this gene should be considered not only in BBS patients but also in individuals with non-syndromic IRD or IRD with very mild extra-ocular manifestations.
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Affiliation(s)
- Iris Deitch
- Rabin Medical Center, Department of Ophthalmology, Petach Tikva 4941492, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Sofia Itskov
- Ruth & Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 3109601, Israel
| | - Daan Panneman
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Aasem Abu Shtaya
- Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petach Tikva 4941492, Israel
- Unit of Gastroenterology, Carmel Medical Center, Haifa 3436212, Israel
| | - Tal Saban
- Rabin Medical Center, Department of Ophthalmology, Petach Tikva 4941492, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Yael Goldberg
- Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
- Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Hospital, Petach Tikva 4941492, Israel
| | - Miriam Ehrenberg
- Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
- Schneider Children's Medical Center of Israel, Department of Ophthalmology, Petach Tikva 4920235, Israel
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Susanne Roosing
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Tamar Ben-Yosef
- Ruth & Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 3109601, Israel
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3
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Conway MP, Stephenson KAJ, Zhu J, Dockery A, Burke T, Turner J, Le FT, O’Byrne JJ, Keegan DJ. The Role of the Ophthalmic Genetics Multidisciplinary Team in the Management of Inherited Retinal Degenerations-A Case-Based Review. Life (Basel) 2024; 14:107. [PMID: 38255722 PMCID: PMC10817299 DOI: 10.3390/life14010107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 01/03/2024] [Accepted: 01/05/2024] [Indexed: 01/24/2024] Open
Abstract
(1) Background: Inherited retinal degenertions are rare conditions which may have a dramatic impact on the daily life of those affected and how they interact with their environment. Coordination of clinical services via an ophthalmic genetics multidisciplinary team (OG-MDT) allows better efficiency of time and resources to reach diagnoses and facilitate patient needs. (2) Methods: This clinical case series was conducted by a retrospective review of patient records for patients enrolled in the Target 5000 programme and managed by the OG-MDT, at the Mater Hospital Dublin, Ireland (n = 865) (3) Results: Herein we describe clinical cases and how the use of the OG-MDT optimizes care for isolated and syndromic IRD pedigrees. (4) Conclusions: this paper demonstrates the benefits of an OG-MDT to patients with IRDs resulting in the holistic resolution of complex and syndromic cases. Furthermore, we demonstrate that this format can be adopted/developed by similar centres around the world, bringing with it the myriad benefits.
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Affiliation(s)
- Marcus P. Conway
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - Kirk A. J. Stephenson
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - Julia Zhu
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - Adrian Dockery
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - Tomas Burke
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - Jacqueline Turner
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - Francois Thai Le
- Eye Clinic Liasson Officer, Vision Ireland, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland;
| | - James J. O’Byrne
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
| | - David J. Keegan
- Mater Clinical Ophthalmic Genetics Unit, Mater Misericordiae University Hospital, D07 AX57 Dublin, Ireland (D.J.K.)
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4
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Guimaraes TACD, Arram E, Shakarchi AF, Georgiou M, Michaelides M. Inherited causes of combined vision and hearing loss: clinical features and molecular genetics. Br J Ophthalmol 2023; 107:1403-1414. [PMID: 36162969 DOI: 10.1136/bjo-2022-321790] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 09/07/2022] [Indexed: 11/04/2022]
Abstract
Combined vision and hearing loss, also known as dual sensory impairment, can occur in several genetic conditions, including ciliopathies such as Usher and Bardet-Biedl syndrome, mitochondrial DNA disorders and systemic diseases, such as CHARGE, Stickler, Waardenburg, Alport and Alstrom syndrome. The retinal phenotype may point to the diagnosis of such disorders. Herein, we aim to provide a comprehensive review of the molecular genetics and clinical features of the most common non-chromosomal inherited disorders to cause dual sensory impairment.
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Affiliation(s)
| | - Elizabeth Arram
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Ahmed F Shakarchi
- Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Michalis Georgiou
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
- UCL Institute of Ophthalmology, University College London, London, UK
- Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA
| | - Michel Michaelides
- Moorfields Eye Hospital NHS Foundation Trust, London, UK
- UCL Institute of Ophthalmology, University College London, London, UK
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5
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Malvasi M, Casillo L, Avogaro F, Abbouda A, Vingolo EM. Gene Therapy in Hereditary Retinal Dystrophies: The Usefulness of Diagnostic Tools in Candidate Patient Selections. Int J Mol Sci 2023; 24:13756. [PMID: 37762059 PMCID: PMC10531171 DOI: 10.3390/ijms241813756] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 08/24/2023] [Accepted: 08/29/2023] [Indexed: 09/29/2023] Open
Abstract
PURPOSE Gene therapy actually seems to have promising results in the treatment of Leber Congenital Amaurosis and some different inherited retinal diseases (IRDs); the primary goal of this strategy is to change gene defects with a wild-type gene without defects in a DNA sequence to achieve partial recovery of the photoreceptor function and, consequently, partially restore lost retinal functions. This approach led to the introduction of a new drug (voretigene neparvovec-rzyl) for replacement of the RPE65 gene in patients affected by Leber Congenital Amaurosis (LCA); however, the treatment results are inconstant and with variable long-lasting effects due to a lack of correctly evaluating the anatomical and functional conditions of residual photoreceptors. These variabilities may also be related to host immunoreactive reactions towards the Adenovirus-associated vector. A broad spectrum of retinal dystrophies frequently generates doubt as to whether the disease or the patient is a good candidate for a successful gene treatment, because, very often, different diseases share similar genetic characteristics, causing an inconstant genotype/phenotype correlation between clinical characteristics also within the same family. For example, mutations on the RPE65 gene cause Leber Congenital Amaurosis (LCA) but also some forms of Retinitis Pigmentosa (RP), Bardet Biedl Syndrome (BBS), Congenital Stationary Night Blindness (CSNB) and Usher syndrome (USH), with a very wide spectrum of clinical manifestations. These confusing elements are due to the different pathways in which the product protein (retinoid isomer-hydrolase) is involved and, consequently, the overlapping metabolism in retinal function. Considering this point and the cost of the drug (over USD one hundred thousand), it would be mandatory to follow guidelines or algorithms to assess the best-fitting disease and candidate patients to maximize the output. Unfortunately, at the moment, there are no suggestions regarding who to treat with gene therapy. Moreover, gene therapy might be helpful in other forms of inherited retinal dystrophies, with more frequent incidence of the disease and better functional conditions (actually, gene therapy is proposed only for patients with poor vision, considering possible side effects due to the treatment procedures), in which this approach leads to better function and, hopefully, visual restoration. But, in this view, who might be a disease candidate or patient to undergo gene therapy, in relationship to the onset of clinical trials for several different forms of IRD? Further, what is the gold standard for tests able to correctly select the patient? Our work aims to evaluate clinical considerations on instrumental morphofunctional tests to assess candidate subjects for treatment and correlate them with clinical and genetic defect analysis that, often, is not correspondent. We try to define which parameters are an essential and indispensable part of the clinical rationale to select patients with IRDs for gene therapy. This review will describe a series of models used to characterize retinal morphology and function from tests, such as optical coherence tomography (OCT) and electrophysiological evaluation (ERG), and its evaluation as a primary outcome in clinical trials. A secondary aim is to propose an ancillary clinical classification of IRDs and their accessibility based on gene therapy's current state of the art. MATERIAL AND METHODS OCT, ERG, and visual field examinations were performed in different forms of IRDs, classified based on clinical and retinal conditions; compared to the gene defect classification, we utilized a diagnostic algorithm for the clinical classification based on morphofunctional information of the retina of patients, which could significantly improve diagnostic accuracy and, consequently, help the ophthalmologist to make a correct diagnosis to achieve optimal clinical results. These considerations are very helpful in selecting IRD patients who might respond to gene therapy with possible therapeutic success and filter out those in which treatment has a lower chance or no chance of positive results due to bad retinal conditions, avoiding time-consuming patient management with unsatisfactory results.
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Affiliation(s)
- Mariaelena Malvasi
- Department of Sense Organs, Faculty of Medicine and Dentistry, Sapienza University of Rome, 00185 Rome, Italy; (L.C.); (E.M.V.)
| | - Lorenzo Casillo
- Department of Sense Organs, Faculty of Medicine and Dentistry, Sapienza University of Rome, 00185 Rome, Italy; (L.C.); (E.M.V.)
| | - Filippo Avogaro
- Department of Sense Organs, Faculty of Medicine and Dentistry, Sapienza University of Rome, 00185 Rome, Italy; (L.C.); (E.M.V.)
| | - Alessandro Abbouda
- Department of Ophthalmology, Fiorini Hospital Terracina AUSL, 04019 Terracina, Italy
| | - Enzo Maria Vingolo
- Department of Sense Organs, Faculty of Medicine and Dentistry, Sapienza University of Rome, 00185 Rome, Italy; (L.C.); (E.M.V.)
- Department of Ophthalmology, Fiorini Hospital Terracina AUSL, 04019 Terracina, Italy
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Khan S, Focșa IO, Budișteanu M, Stoica C, Nedelea F, Bohîlțea L, Caba L, Butnariu L, Pânzaru M, Rusu C, Jurcă C, Chirita-Emandi A, Bănescu C, Abbas W, Sadeghpour A, Baig SM, Bălgrădean M, Davis EE. Exome sequencing in a Romanian Bardet-Biedl syndrome cohort revealed an overabundance of causal BBS12 variants. Am J Med Genet A 2023; 191:2376-2391. [PMID: 37293956 PMCID: PMC10524726 DOI: 10.1002/ajmg.a.63322] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 05/16/2023] [Accepted: 05/26/2023] [Indexed: 06/10/2023]
Abstract
Bardet-Biedl syndrome (BBS), is an emblematic ciliopathy hallmarked by pleiotropy, phenotype variability, and extensive genetic heterogeneity. BBS is a rare (~1/140,000 to ~1/160,000 in Europe) autosomal recessive pediatric disorder characterized by retinal degeneration, truncal obesity, polydactyly, cognitive impairment, renal dysfunction, and hypogonadism. Twenty-eight genes involved in ciliary structure or function have been implicated in BBS, and explain the molecular basis for ~75%-80% of individuals. To investigate the mutational spectrum of BBS in Romania, we ascertained a cohort of 24 individuals in 23 families. Following informed consent, we performed proband exome sequencing (ES). We detected 17 different putative disease-causing single nucleotide variants or small insertion-deletions and two pathogenic exon disruptive copy number variants in known BBS genes in 17 pedigrees. The most frequently impacted genes were BBS12 (35%), followed by BBS4, BBS7, and BBS10 (9% each) and BBS1, BBS2, and BBS5 (4% each). Homozygous BBS12 p.Arg355* variants were present in seven pedigrees of both Eastern European and Romani origin. Our data show that although the diagnostic rate of BBS in Romania is likely consistent with other worldwide cohorts (74%), we observed a unique distribution of causal BBS genes, including overrepresentation of BBS12 due to a recurrent nonsense variant, that has implications for regional diagnostics.
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Affiliation(s)
- Sheraz Khan
- Stanley Manne Children's Research Institute, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
- Human Molecular Genetics Lab, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE-C), Faisalabad, Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Ina Ofelia Focșa
- University of Medicine and Pharmacy "Carol Davila", Bucharest, Romania
- Cytogenomic Medical Laboratory, Bucharest, Romania
| | - Magdalena Budișteanu
- Psychiatry Research Laboratory, "Prof. Dr. Alexandru Obregia" Clinical Hospital of Psychiatry, Bucharest, Romania
- Medical Genetic Laboratory, "Victor Babeș" National Institute of Pathology, Bucharest, Romania
- Department of Medical Genetics, Faculty of Medicine, "Titu Maiorescu" University, Bucharest, Romania
| | - Cristina Stoica
- University of Medicine and Pharmacy "Carol Davila", Bucharest, Romania
- Department of Pediatrics, Clinical Institute Fundeni, Bucharest, Romania
| | - Florina Nedelea
- University of Medicine and Pharmacy "Carol Davila", Bucharest, Romania
- Genetics Department, Clinical Hospital Filantropia, Bucharest, Romania
| | | | - Lavinia Caba
- Department of Medical Genetics, "Grigore T. Popa" University of Medicine and Pharmacy, Iași, Romania
| | - Lăcrămioara Butnariu
- Department of Medical Genetics, "Grigore T. Popa" University of Medicine and Pharmacy, Iași, Romania
- Regional Medical Genetics Centre, "Sf. Maria" Children's Hospital, Iași, Romania
| | - Monica Pânzaru
- Department of Medical Genetics, "Grigore T. Popa" University of Medicine and Pharmacy, Iași, Romania
- Regional Medical Genetics Centre, "Sf. Maria" Children's Hospital, Iași, Romania
| | - Cristina Rusu
- Department of Medical Genetics, "Grigore T. Popa" University of Medicine and Pharmacy, Iași, Romania
- Regional Medical Genetics Centre, "Sf. Maria" Children's Hospital, Iași, Romania
| | - Claudia Jurcă
- Department of Genetics, Faculty of Medicine and Pharmacy, University of Oradea, Oradea, Romania
- Department of Pediatrics, "Dr. Gavril Curteanu" Municipal Clinical Hospital, Oradea, Romania
| | - Adela Chirita-Emandi
- Emergency Hospital for Children Louis Turcanu, Regional Center of Medical Genetics Timis, Timisoara, Romania
- Victor Babes University of Medicine and Pharmacy Timisoara, Department of Microscopic Morphology Genetics, Center for Genomic Medicine, Timisoara, Romania
| | - Claudia Bănescu
- "George Emil Palade" University of Medicine, Pharmacy, Sciences and Technology, Târgu Mureş, Romania
| | - Wasim Abbas
- Human Molecular Genetics Lab, Health Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE-C), Faisalabad, Pakistan
- Pakistan Institute of Engineering and Applied Sciences (PIEAS), Islamabad, Pakistan
| | - Azita Sadeghpour
- Center for Human Disease Modeling, Duke University Medical Center, Durham, North Carolina, USA
- Duke Precision Medicine Program, Department of Medicine, Division of General Internal Medicine, Duke University Medical Center, Durham, NC, USA
| | - Shahid Mahmood Baig
- Pakistan Science Foundation (PSF), Islamabad, Pakistan
- Department of Biological and Biomedical Sciences, Agha Khan University Karachi, Karachi, Pakistan
| | - Mihaela Bălgrădean
- University of Medicine and Pharmacy "Carol Davila", Bucharest, Romania
- Department of Pediatrics and Pediatric Nephrology, Emergency Clinical Hospital for Children "Maria Skłodowska Curie", Bucharest, Romania
| | - Erica E Davis
- Stanley Manne Children's Research Institute, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
- Department of Pediatrics and Department of Cell and Developmental Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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7
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Melluso A, Secondulfo F, Capolongo G, Capasso G, Zacchia M. Bardet-Biedl Syndrome: Current Perspectives and Clinical Outlook. Ther Clin Risk Manag 2023; 19:115-132. [PMID: 36741589 PMCID: PMC9896974 DOI: 10.2147/tcrm.s338653] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 01/20/2023] [Indexed: 02/04/2023] Open
Abstract
The Bardet Biedl syndrome (BBS) is a rare inherited disorder considered a model of non-motile ciliopathy. It is in fact caused by mutations of genes encoding for proteins mainly localized to the base of the cilium. Clinical features of BBS patients are widely shared with patients suffering from other ciliopathies, especially autosomal recessive syndromic disorders; moreover, mutations in cilia-related genes can cause different clinical ciliopathy entities. Besides the best-known clinical features, as retinal degeneration, learning disabilities, polydactyly, obesity and renal defects, several additional clinical signs have been reported in BBS, expanding our understanding of the complexity of its clinical spectrum. The present review aims to describe the current knowledge of BBS i) pathophysiology, ii) clinical manifestations, highlighting both the most common and the less described features, iii) current and future perspective for treatment.
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Affiliation(s)
- Andrea Melluso
- Department of Translational Medical Sciences, University of Campania “Luigi Vanvitelli”, Naples, Italy
| | - Floriana Secondulfo
- Department of Translational Medical Sciences, University of Campania “Luigi Vanvitelli”, Naples, Italy
| | - Giovanna Capolongo
- Department of Translational Medical Sciences, University of Campania “Luigi Vanvitelli”, Naples, Italy
| | - Giovambattista Capasso
- Department of Translational Medical Sciences, University of Campania “Luigi Vanvitelli”, Naples, Italy,Biogem Scarl, Ariano Irpino, AV, 83031, Italy
| | - Miriam Zacchia
- Department of Translational Medical Sciences, University of Campania “Luigi Vanvitelli”, Naples, Italy,Correspondence: Miriam Zacchia, Via Pansini 5, Naples, 80131, Italy, Tel +39 081 566 6650, Fax +39 081 566 6671, Email
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8
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Gupta N, Khan MA, Capasso G, Zacchia M. Computational and Structural Analysis to Assess the Pathogenicity of Bardet-Biedl Syndrome Related Missense Variants Identified in Bardet-Biedl Syndrome 10 Gene (BBS10). ACS OMEGA 2022; 7:37654-37662. [PMID: 36312387 PMCID: PMC9608418 DOI: 10.1021/acsomega.2c04522] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 09/28/2022] [Indexed: 05/27/2023]
Abstract
Bardet-Biedl Syndrome (BBS) is a rare inherited disorder resulting in multiple organ dysfunctions, whose cardinal clinical features include cognitive impairment, obesity, and renal dysfunction. Although it is highly heterogeneous at genetic levels, BBS10 is one of the major causative genes worldwide. The BBS10 protein is part of a multiprotein complex localized at the basal body of the primary cilium. With the advancement of sequencing technologies, novel missense mutations are regularly reported in BBS10. However, prioritizing missense variants and conducting further in-depth analysis are key challenges in addressing their pathogenic effect. This study aims to characterize the known missense mutations of BBS10 by combining nine different in silico tools (SIFT, SNAP2, PROVEAN, Align-GVGD, ConSurf, I Mutant, MuPro, PremPS, and Dynamut) and molecular dynamics (MD) simulations. A total of 101 BBS10 missense variants have been analyzed. Our results showed that six BBS10 missense variants (Ser191Leu, Cys19Gly, Ile342Thr, Cys371Ser, Ala417Glu, and Tyr613Cys) were potentially deleterious. Overall, this study provides a comprehensive workflow for screening BBS10 missense mutations to identify pathogenic variants effectively.
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Affiliation(s)
- Neha Gupta
- Unit
of Nephrology, Department of Translational Medical Sciences, University of Campania, L. Vanvitelli, Via Leonardo Bianchi, 80131 Naples, Italy
- BioGem
S.C.A.R.L., Contrada Camporeale, 83031 Ariano Irpino
AV, Italy
| | - Mudassar Ali Khan
- Advanced
Centre for Treatment, Research and Education
in Cancer, Kharghar, Navi Mumbai, Maharashtra 410210, India
- Homi
Bhabha National Institute, Training School
Complex, Anushaktinagar, Mumbai 400094, India
| | - Giovambattista Capasso
- Unit
of Nephrology, Department of Translational Medical Sciences, University of Campania, L. Vanvitelli, Via Leonardo Bianchi, 80131 Naples, Italy
- BioGem
S.C.A.R.L., Contrada Camporeale, 83031 Ariano Irpino
AV, Italy
| | - Miriam Zacchia
- Unit
of Nephrology, Department of Translational Medical Sciences, University of Campania, L. Vanvitelli, Via Leonardo Bianchi, 80131 Naples, Italy
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9
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Nasser F, Kohl S, Kurtenbach A, Kempf M, Biskup S, Zuleger T, Haack TB, Weisschuh N, Stingl K, Zrenner E. Ophthalmic and Genetic Features of Bardet Biedl Syndrome in a German Cohort. Genes (Basel) 2022; 13:genes13071218. [PMID: 35886001 PMCID: PMC9322102 DOI: 10.3390/genes13071218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Revised: 06/29/2022] [Accepted: 07/02/2022] [Indexed: 12/04/2022] Open
Abstract
The aim of this study was to characterize the ophthalmic and genetic features of Bardet Biedl (BBS) syndrome in a cohort of patients from a German specialized ophthalmic care center. Sixty-one patients, aged 5−56 years, underwent a detailed ophthalmic examination including visual acuity and color vision testing, electroretinography (ERG), visually evoked potential recording (VEP), fundus examination, and spectral domain optical coherence tomography (SD-OCT). Adaptive optics flood illumination ophthalmoscopy was performed in five patients. All patients had received diagnostic genetic testing and were selected upon the presence of apparent biallelic variants in known BBS-associated genes. All patients had retinal dystrophy with morphologic changes of the retina. Visual acuity decreased from ~0.2 (decimal) at age 5 to blindness 0 at 50 years. Visual field examination could be performed in only half of the patients and showed a concentric constriction with remaining islands of function in the periphery. ERG recordings were mostly extinguished whereas VEP recordings were reduced in about half of the patients. The cohort of patients showed 51 different likely biallelic mutations—of which 11 are novel—in 12 different BBS-associated genes. The most common associated genes were BBS10 (32.8%) and BBS1 (24.6%), and by far the most commonly observed variants were BBS10 c.271dup;p.C91Lfs*5 (21 alleles) and BBS1 c.1169T>G;p.M390R (18 alleles). The phenotype associated with the different BBS-associated genes and genotypes in our cohort is heterogeneous, with diverse features without genotype−phenotype correlation. The results confirm and expand our knowledge of this rare disease.
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Affiliation(s)
- Fadi Nasser
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
- Department of Ophthalmology, University of Leipzig, 04103 Leipzig, Germany
- Correspondence:
| | - Susanne Kohl
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
| | - Anne Kurtenbach
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
| | - Melanie Kempf
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
- Center for Rare Eye Diseases, University of Tübingen, 72076 Tuebingen, Germany
| | | | - Theresia Zuleger
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, 72076 Tuebingen, Germany; (T.Z.); (T.B.H.)
| | - Tobias B. Haack
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, 72076 Tuebingen, Germany; (T.Z.); (T.B.H.)
| | - Nicole Weisschuh
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
| | - Katarina Stingl
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
- Center for Rare Eye Diseases, University of Tübingen, 72076 Tuebingen, Germany
| | - Eberhart Zrenner
- Centre for Ophthalmology, University of Tübingen, 72076 Tuebingen, Germany; (S.K.); (A.K.); (M.K.); (N.W.); (K.S.); (E.Z.)
- Werner Reichardt Centre for Integrative Neuroscience (CIN), University of Tübingen, 72076 Tuebingen, Germany
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Gupta N, D'Acierno M, Zona E, Capasso G, Zacchia M. Bardet-Biedl syndrome: The pleiotropic role of the chaperonin-like BBS6, 10, and 12 proteins. AMERICAN JOURNAL OF MEDICAL GENETICS. PART C, SEMINARS IN MEDICAL GENETICS 2022; 190:9-19. [PMID: 35373910 PMCID: PMC9325507 DOI: 10.1002/ajmg.c.31970] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 02/08/2022] [Accepted: 03/27/2022] [Indexed: 12/11/2022]
Abstract
Bardet–Biedl syndrome (BBS) is a rare pleiotropic disorder known as a ciliopathy. Despite significant genetic heterogeneity, BBS1 and BBS10 are responsible for major diagnosis in western countries. It is well established that eight BBS proteins, namely BBS1, 2, 4, 5, 7, 8, 9, and 18, form the BBSome, a multiprotein complex serving as a regulator of ciliary membrane protein composition. Less information is available for BBS6, BBS10, and BBS12, three proteins showing sequence homology with the CCT/TRiC family of group II chaperonins. Even though their chaperonin function is debated, scientific evidence demonstrated that they are required for initial BBSome assembly in vitro. Recent studies suggest that genotype may partially predict clinical outcomes. Indeed, patients carrying truncating mutations in any gene show the most severe phenotype; moreover, mutations in chaperonin‐like BBS proteins correlated with severe kidney impairment. This study is a critical review of the literature on genetics, expression level, cellular localization and function of BBS proteins, focusing primarily on the chaperonin‐like BBS proteins, and aiming to provide some clues to understand the pathomechanisms of disease in this setting.
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Affiliation(s)
- Neha Gupta
- Unit of Nephrology, Department of Translational Medical Sciences, University of Campania L. Vanvitelli, Naples, Italy.,BioGem S.C.A.R.L., Benevento, Benevento Province, Italy
| | - Mariavittoria D'Acierno
- Unit of Nephrology, Department of Translational Medical Sciences, University of Campania L. Vanvitelli, Naples, Italy.,BioGem S.C.A.R.L., Benevento, Benevento Province, Italy
| | - Enrica Zona
- Unit of Nephrology, Department of Translational Medical Sciences, University of Campania L. Vanvitelli, Naples, Italy
| | | | - Miriam Zacchia
- Unit of Nephrology, Department of Translational Medical Sciences, University of Campania L. Vanvitelli, Naples, Italy
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Guardiola GA, Ramos F, Izquierdo NJ, Oliver AL. A Genotype-Phenotype Analysis of the Bardet-Biedl Syndrome in Puerto Rico. Clin Ophthalmol 2021; 15:3757-3764. [PMID: 34526762 PMCID: PMC8435472 DOI: 10.2147/opth.s328493] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 08/23/2021] [Indexed: 12/15/2022] Open
Abstract
Background Bardet-Biedl syndrome is a complex heterogeneous ciliopathy caused by genetic mutations. Although establishing genotype-phenotype correlations has been challenging, some regional variations have been previously reported. Due to its relative geographic isolation, Puerto Rico has a greater prevalence of Bardet-Biedl syndrome than do other regions. We sought to characterize the most frequent genotypic variations in a local cohort of Bardet-Biedl syndrome patients and report any genotypic-phenotypic trends. Methods Twenty-seven patients from an ophthalmology clinic in Puerto Rico with genetically confirmed Bardet-Biedl syndrome took a questionnaire inquiring about their most common symptoms. Ophthalmological information was obtained from patient records. The frequencies of the genotypic variations and symptoms were calculated. Results In the study population, BBS1 was the most prevalent mutated gene, followed by BBS7. In the BBS1 group, we found homozygotes for c.1169T>G (p.Met390Arg) and c.1645G>T (p.Glu549*), and compound heterozygotes for c.1169T>G (p.Met390Arg) and c.1645G>T (p.Glu549*), with one patient having c.1645G>T (p.Glu549*) and c.432+1G>A (splice donor). All the BBS7 patients were homozygous for c.632C>T (p.Thr211Ile). Compared to BBS7, we found that BBS1 patients generally had a milder ocular and systemic phenotype. However, when analyzing different BBS1 variants, patients with mutations in c.1645G>T (p.Glu549*), both compound heterozygous and homozygous, had more severe systemic phenotypes, overall. Conclusion Our study was the first detailed genotype-phenotype analysis of the Bardet-Biedl syndrome in Puerto Rico. Genetic mutations in BBS1 and BBS7 seem to be the most common culprits behind Bardet-Biedl syndrome in this population. Although patients diagnosed with BBS1 are likely to display milder systemic features, this was not the case with our BBS1 patients having the c.1645G>T (p.Glu549*) mutation. Further studies should focus on the c.1645G>T (p.Glu549*) mutation's impact on the BBS1 gene and protein product.
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Affiliation(s)
- Gabriel A Guardiola
- Department of Medicine, Universidad Central del Caribe School of Medicine, Bayamon, PR, USA
| | - Fabiola Ramos
- Department of Ophthalmology, University of Puerto Rico School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR, USA
| | - Natalio J Izquierdo
- Department of Surgery, University of Puerto Rico School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR, USA
| | - Armando L Oliver
- Department of Ophthalmology, University of Puerto Rico School of Medicine, University of Puerto Rico, Medical Sciences Campus, San Juan, PR, USA
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12
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Bardet-Biedl Syndrome-Multiple Kaleidoscope Images: Insight into Mechanisms of Genotype-Phenotype Correlations. Genes (Basel) 2021; 12:genes12091353. [PMID: 34573333 PMCID: PMC8465569 DOI: 10.3390/genes12091353] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 08/22/2021] [Accepted: 08/27/2021] [Indexed: 01/04/2023] Open
Abstract
Bardet-Biedl Syndrome is a rare non-motile primary ciliopathy with multisystem involvement and autosomal recessive inheritance. The clinical picture is extremely polymorphic. The main clinical features are retinal cone-rod dystrophy, central obesity, postaxial polydactyly, cognitive impairment, hypogonadism and genitourinary abnormalities, and kidney disease. It is caused by various types of mutations, mainly in genes encoding BBSome proteins, chaperonins, and IFT complex. Variable expressivity and pleiotropy are correlated with the existence of multiple genes and variants modifiers. This review is focused on the phenomena of heterogeneity (locus, allelic, mutational, and clinical) in Bardet-Biedl Syndrome, its mechanisms, and importance in early diagnosis and proper management.
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13
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Suárez-González J, Seidel V, Andrés-Zayas C, Izquierdo E, Buño I. Novel biallelic variant in BBS9 causative of Bardet-Biedl syndrome: expanding the spectrum of disease-causing genetic alterations. BMC Med Genomics 2021; 14:91. [PMID: 33771153 PMCID: PMC7995718 DOI: 10.1186/s12920-021-00943-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 03/16/2021] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Bardet-Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy disorder. Many BBS disease-causing genetic variants have been identified due to the advancement of molecular diagnostic tools. We report on a novel pathogenic variant in a consanguineous Pakistani family with an affected child. CASE PRESENTATION Clinical exome sequencing was used to search for BBS causing variants in the affected individual and identified a novel homozygous splice-site variant in the BBS9 gene (c.702 + 1del). Sanger sequencing was performed for variant validation and segregation studies. Expression analysis using mRNA levels to assess the functional impact of the novel variant demonstrated skipping of exon 7 in the affected alleles, suggesting a truncating effect. Three-dimensional structural modelling was used to predict pathogenicity of the variant residue and the alteration leads to a partial deletion of the PHTB1_N domain and a total deletion of the PHTB1_C domain. CONCLUSION The study of this case expands the spectrum of biallelic variants in the BBS9 gene associated with BBS and increased the knowledge on the molecular consequences of splicing variation c.702 + 1del.
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Affiliation(s)
- Julia Suárez-González
- Genomics Unit, Gregorio Marañón General University Hospital, Gregorio Marañón Health Research Institute (IiSGM), C/Doctor Esquerdo 46, 28007, Madrid, Spain
- Gregorio Marañón Health Research Institute (IiSGM), Madrid, Spain
| | - Verónica Seidel
- Clinical Genetics, Department of Pediatrics, Gregorio Marañón General University Hospital, Madrid, Spain
| | - Cristina Andrés-Zayas
- Genomics Unit, Gregorio Marañón General University Hospital, Gregorio Marañón Health Research Institute (IiSGM), C/Doctor Esquerdo 46, 28007, Madrid, Spain
- Gregorio Marañón Health Research Institute (IiSGM), Madrid, Spain
| | - Elvira Izquierdo
- Pediatric Nephrology, Department of Pediatrics, Gregorio Marañón General University Hospital, Madrid, Spain
| | - Ismael Buño
- Genomics Unit, Gregorio Marañón General University Hospital, Gregorio Marañón Health Research Institute (IiSGM), C/Doctor Esquerdo 46, 28007, Madrid, Spain.
- Gregorio Marañón Health Research Institute (IiSGM), Madrid, Spain.
- Department of Hematology, Gregorio Marañón General University Hospital, Madrid, Spain.
- Department of Cell Biology, School of Medicine, Complutense University of Madrid, Madrid, Spain.
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Beigi F, Del Pozo-Valero M, Martin-Merida I, Perea-Romero I, Manaviat MR, Ayuso C, Ghasemi N. Apparent but unconfirmed digenism in an Iranian consanguineous family with syndromic Retinal Disease. Exp Eye Res 2021; 207:108533. [PMID: 33741323 DOI: 10.1016/j.exer.2021.108533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 02/23/2021] [Accepted: 02/28/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Bardet-Biedl syndrome is an autosomal recessive disease characterized by rod-cone dystrophy, postaxial polydactyly, kidney defects, obesity, mental retardation and hypogonadism. Here, we report different genotypes in two Bardet-Biedl syndrome affected sisters with a different clinical phenotype regarding severity. MATERIALS AND METHODS The proband of the family was examined by Next Generation Sequencing (NGS) using clinical exome and filtering by syndromic and non-syndromic genes associated with retinal dystrophies. RESULTS Targeted NGS revealed two novel variants in the MKKS and CEP290 genes in homozygosis state in the proband. Segregation analysis revealed the presence of the same MKKS homozygous variant in her younger affected sister but not the CEP290 variant. Both sisters presented different clinical manifestation, at different ages, with a more severe renal and retinal defect in the case of the sister carrying mutations in both genes. Another unaffected sister showed only homozygosity for the CEP290 variant, thus supporting the non-pathogenic role of this mutation in BBS phenotype. CONCLUSIONS In this study, NGS proved to be a powerful and efficient sequencing method to identify causal variants in different genes. However, it remarks the importance of the segregation analysis and clinical information to establish the pathogenicity of new variants. The two affected sisters present different genotypes and clinical manifestation, suggesting that the novel CEP290 variant could be acting as a modifier, making the phenotype more severe in the sister homozygote for MKKS and CEP290 genes. On the other hand, the difference in the age of both sisters highlight the important role of monitoring disease progression also to confirm the modifier role of genetic variants.
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Affiliation(s)
- Fahimeh Beigi
- Department of Medical Genetics, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Marta Del Pozo-Valero
- Department of Clinical Genetics and Genomics, University Hospital Fundacion Jimenez Diaz, Health Research Institute Fundacion Jimenez Diaz (IIS-FJD, UAM), Madrid, Spain; CIBERER (Biomedical Research Network Centre for Rare Diseases), ISCIII, Madrid, Spain
| | - Inmaculada Martin-Merida
- Department of Clinical Genetics and Genomics, University Hospital Fundacion Jimenez Diaz, Health Research Institute Fundacion Jimenez Diaz (IIS-FJD, UAM), Madrid, Spain; CIBERER (Biomedical Research Network Centre for Rare Diseases), ISCIII, Madrid, Spain
| | - Irene Perea-Romero
- Department of Clinical Genetics and Genomics, University Hospital Fundacion Jimenez Diaz, Health Research Institute Fundacion Jimenez Diaz (IIS-FJD, UAM), Madrid, Spain; CIBERER (Biomedical Research Network Centre for Rare Diseases), ISCIII, Madrid, Spain
| | - Masoud Reza Manaviat
- Department of Ophthalmology, Shahid Sadoughi University of Medical Science, Yazd Diabetes Research Center, Yazd, Iran
| | - Carmen Ayuso
- Department of Clinical Genetics and Genomics, University Hospital Fundacion Jimenez Diaz, Health Research Institute Fundacion Jimenez Diaz (IIS-FJD, UAM), Madrid, Spain; CIBERER (Biomedical Research Network Centre for Rare Diseases), ISCIII, Madrid, Spain
| | - Nasrin Ghasemi
- Abortion Research Centre, Reproductive Sciences Institute, Yazd Shahid Sadoughi University of Medical Sciences and Health Services, Yazd, Iran.
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Identification of a Novel Homozygous Missense (c.443A>T:p.N148I) Mutation in BBS2 in a Kashmiri Family with Bardet-Biedl Syndrome. BIOMED RESEARCH INTERNATIONAL 2021; 2021:6626015. [PMID: 33688495 PMCID: PMC7925018 DOI: 10.1155/2021/6626015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 12/31/2020] [Accepted: 01/31/2021] [Indexed: 11/17/2022]
Abstract
Background Bardet-Biedl syndrome (BBS) is a rare autosomal recessive inherited disorder with distinctive clinical feature such as obesity, degeneration of retina, polydactyly, and renal abnormalities. The study was aimed at finding out the disease-causing variant/s in patients exhibiting clinical features of BBS. Methods The identification of disease-causing variant was done by using whole exome sequencing on Illumina HiSeq 4000 platform involving the SeqCap EZ Exome v3 kit (Roche NimbleGen). The identified variant was further validated by Sanger sequencing. Results WES revealed a novel homozygous missense mutation (NM_031885: c.443A>T:p.N148I) in exon 3 of the BBS2 gene. Sanger sequencing confirmed this variant as homozygous in both affected subjects and heterozygous in obligate parents, demonstrating autosomal recessive inheritance pattern. To the best of our knowledge, this variant was not present in literature and all publically available databases. The candidate variant is predicted to be pathogenic by a set of in-silico softwares. Conclusion Clinical and genetic spectrum of BBS and BBS-like disorders is not completely defined in the Pakistani as well as in Kashmiri population. Therefore, more comprehensive genetic studies are required to gain insights into genotype-phenotype associations to facilitate carrier screening and genetic counseling of families with such disorders.
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Pomeroy J, Krentz AD, Richardson JG, Berg RL, VanWormer JJ, Haws RM. Bardet-Biedl syndrome: Weight patterns and genetics in a rare obesity syndrome. Pediatr Obes 2021; 16:e12703. [PMID: 32700463 PMCID: PMC7816264 DOI: 10.1111/ijpo.12703] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Accepted: 06/30/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Bardet-Biedl syndrome (BBS) is a rare genetic disorder that severely inhibits primary cilia function. BBS is typified by obesity in adulthood, but pediatric weight patterns, and thus optimal periods of intervention, are poorly understood. OBJECTIVES To examine body mass differences by age, gender, and genotype in children and adolescents with BBS. METHODS We utilized the largest international registry of BBS phenotypes. Anthropometric and genetic data were obtained from medical records or participant/family interviews. Participants were stratified by age and sex categories. Genotype and obesity phenotype were investigated in a subset of participants with available data. RESULTS Height and weight measurements were available for 552 unique individuals with BBS. The majority of birth weights were in the normal range, but rates of overweight or obesity rapidly increased in early childhood, exceeding 90% after age 5. Weight z-scores in groups >2 years were above 2.0, while height z-scores approached 1.0, but were close to 0.0 in adolescents. Relative to those with the BBS10 genotype, the BBS1 cohort had a lower BMI z-score in the 2-5 and 6-11 age groups, with similar BMI z-scores thereafter. Children with biallelic loss of function (LOF) genetic variants had significantly higher BMI z-scores compared to missense variants. CONCLUSION Despite normal birth weight, most individuals with BBS experience rapid weight gain in early childhood, with high rates of overweight/obesity sustained through adolescence. Children with LOF variants are disproportionally affected. Our findings support the need for earlier recognition and initiation of weight management therapies in BBS.
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Affiliation(s)
- Jeremy Pomeroy
- Clinical Research CenterMarshfield Clinic Research InstituteMarshfieldWisconsinUSA
| | | | - Jesse G. Richardson
- Clinical Research CenterMarshfield Clinic Research InstituteMarshfieldWisconsinUSA
| | - Richard L. Berg
- Clinical Research CenterMarshfield Clinic Research InstituteMarshfieldWisconsinUSA
| | - Jeffrey J. VanWormer
- Clinical Research CenterMarshfield Clinic Research InstituteMarshfieldWisconsinUSA
| | - Robert M. Haws
- Clinical Research CenterMarshfield Clinic Research InstituteMarshfieldWisconsinUSA,Department of PediatricsMarshfield Clinic Health SystemMarshfieldWisconsinUSA
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BBS Proteins Affect Ciliogenesis and Are Essential for Hedgehog Signaling, but Not for Formation of iPSC-Derived RPE-65 Expressing RPE-Like Cells. Int J Mol Sci 2021; 22:ijms22031345. [PMID: 33572860 PMCID: PMC7866284 DOI: 10.3390/ijms22031345] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/23/2021] [Accepted: 01/24/2021] [Indexed: 12/31/2022] Open
Abstract
Bardet-Biedl syndrome (BBS) is a ciliopathy characterized by retinal dystrophy, renal cysts, obesity and polydactyly. BBS genes have been implicated in ciliogenesis, hedgehog signaling and retinal pigment epithelium maturation. BBS1 and BBS5 are members of the BBSome, implicated in cilia transport of proteins, and BBS10 is a member of the chaperonin-complex, mediating BBSome assembly. In this study, involvement of BBS1, BBS5 and BBS10 in ciliogenesis and hedgehog signaling were investigated in BBS-defective patient fibroblasts as well as in RPE-hTERT cells following siRNA-mediated knockdown of the BBS genes. Furthermore, the ability of BBS1-defective induced pluripotent stem-cells (iPSCs) to differentiate into RPE cells was assessed. We report that cells lacking functional BBS5 or BBS10 have a reduced number of primary cilia, whereas cells lacking functional BBS1 display shorter primary cilia compared to wild-type cells. Hedgehog signaling was substantially impaired and Smoothened, a component of hedgehog signaling, was trapped inside the cilia of the BBS-defective cells, even in the absence of Smoothened agonist. Preliminary results demonstrated the ability of BBS1-defective iPSC to differentiate into RPE-65 expressing RPE-like cells. The BBS1-/--defective RPE-like cells were less pigmented, compared to RPE-like cells differentiated from control iPSCs, indicating an impact of BBS1 on RPE maturation.
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Sablok A, Thakur S, Sharma A, Kaul A. Prenatal Diagnosis of Bardet-Biedl Syndrome: A Case Study and Review of Literature. JOURNAL OF FETAL MEDICINE 2020. [DOI: 10.1007/s40556-020-00278-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Holtan JP, Selmer KK, Heimdal KR, Bragadóttir R. Inherited retinal disease in Norway - a characterization of current clinical and genetic knowledge. Acta Ophthalmol 2020; 98:286-295. [PMID: 31429209 DOI: 10.1111/aos.14218] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 07/23/2019] [Indexed: 02/06/2023]
Abstract
PURPOSE The purpose of this study was to characterize current clinical and genetic knowledge of patients with inherited retinal disease in Norway and give an estimate of the prevalence. These data are necessary to identify patients eligible for new personalized medicines, to facilitate genetic counselling for their families and to plan clinical follow-up. METHODS A patient registry including clinical and genetic data was established. Clinical data were retrieved during 2003-2018. Genetic testing was performed in the period 2007-2018. RESULTS The material included 866 patients with 41 clinical diagnoses at the cut-off date. The most prevalent diseases were as follows: retinitis pigmentosa (54%), Stargardt macular dystrophy (6.5%) and Leber congenital amaurosis (5.2%). A genetic diagnosis was identified in 32% of patients. In total, 207 disease-causing variants in 56 genes were reported. The most commonly reported disease-causing genes were ABCA4, USH2A and BEST1. The estimated adjusted minimum prevalence of inherited retinal disease in the south-east region of Norway was 1: 3,856 (2.6/10 000). CONCLUSION This population-based study demonstrated an estimated prevalence for all inherited retinal diseases in south-east Norway and described the distribution of clinical diagnoses, onset of symptoms, inheritance patterns and genetic data and thereby expands our knowledge of inherited retinal disease in Norway. The newly established registry and biobank will support patient feasibility for future clinical trials, treatment selection and counselling of families.
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Affiliation(s)
- Josephine Prener Holtan
- Department of Ophthalmology Oslo University Hospital Oslo Norway
- University of Oslo Oslo Norway
| | - Kaja Kristine Selmer
- Department of Medical Genetics Oslo University Hospital Oslo Norway
- Department of Research and Development Oslo University Hospital Oslo Norway
| | | | - Ragnheiður Bragadóttir
- Department of Ophthalmology Oslo University Hospital Oslo Norway
- University of Oslo Oslo Norway
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Zelihić D, Hjardemaal FR, Lippe CVD. Caring for a child with Bardet-Biedl syndrome: A qualitative study of the parental experiences of daily coping and support. Eur J Med Genet 2020; 63:103856. [PMID: 31972368 DOI: 10.1016/j.ejmg.2020.103856] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/12/2019] [Accepted: 01/17/2020] [Indexed: 10/25/2022]
Abstract
This study aimed to explore the parental experiences of having a child with Bardet-Biedl syndrome (BBS) and how parents managed to cope with this situation. Five parents of children with BBS (0-18 years old) participated in semistructured in-depth interviews. Inductive thematic analysis was used to identify themes. The parents experienced distress due to a lack of knowledge on BBS in their support system (e.g., school staff, clinicians, and family members), and they found it stressful to coordinate with multiple support services. Socialization at work, support from family members, and communicating with other parents who are in a similar situation promoted better coping and adaptations to daily life. Results highlight the importance of parents receiving adequate support while they face daily challenges. An increased knowledge on how rare disorders impact family life is needed in the support system.
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Affiliation(s)
- Deniz Zelihić
- Centre for Rare Disorders, Rikshospitalet, Oslo University Hospital HF, Norway
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Generation and characterization of three isogenic induced pluripotent stem cell lines from a patient with Bardet-Biedl syndrome and homozygous for the BBS5 variant. Stem Cell Res 2019; 41:101594. [PMID: 31760295 DOI: 10.1016/j.scr.2019.101594] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 09/15/2019] [Accepted: 09/19/2019] [Indexed: 11/22/2022] Open
Abstract
Bardet-Biedl syndrome (BBS), an autosomal recessive disease, is associated with non-functional primary cilia. BBS5 is part of the protein complex termed the BBSome. The BBSome associates with intra flagellar transport (IFT) particles and mediates trafficking of membrane proteins in the cilium, a process important for cilia-mediated signal transduction. Here we describe the generation of three induced pluripotent stem cell (iPSC) lines, KCi003-A, KCi003-B and KCi003-C from a patient with BBS and homozygous for the disease causing variant c.214G>A, p.(Gly72Ser) in BBS5. The iPSC lines can be used for investigation of IFT in different cell types differentiated from the iPSC line.
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Niederlova V, Modrak M, Tsyklauri O, Huranova M, Stepanek O. Meta-analysis of genotype-phenotype associations in Bardet-Biedl syndrome uncovers differences among causative genes. Hum Mutat 2019; 40:2068-2087. [PMID: 31283077 DOI: 10.1002/humu.23862] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 06/17/2019] [Accepted: 07/03/2019] [Indexed: 12/16/2022]
Abstract
Bardet-Biedl syndrome (BBS) is a recessive genetic disease causing multiple organ anomalies. Most patients carry mutations in genes encoding for the subunits of the BBSome, an octameric ciliary transport complex, or accessory proteins involved in the BBSome assembly or function. BBS proteins have been extensively studied using in vitro, cellular, and animal models. However, the molecular functions of particular BBS proteins and the etiology of the BBS symptoms are still largely elusive. In this study, we applied a meta-analysis approach to study the genotype-phenotype association in humans using our database of all reported BBS patients. The analysis revealed that the identity of the causative gene and the character of the mutation partially predict the clinical outcome of the disease. Besides their potential use for clinical prognosis, our analysis revealed functional differences of particular BBS genes in humans. Core BBSome subunits BBS2, BBS7, and BBS9 manifest as more critical for the function and development of kidneys than peripheral subunits BBS1, BBS4, and BBS8/TTC8, suggesting that incomplete BBSome retains residual function at least in the kidney.
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Affiliation(s)
- Veronika Niederlova
- Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martin Modrak
- Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Oksana Tsyklauri
- Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Martina Huranova
- Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Ondrej Stepanek
- Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
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Manara E, Paolacci S, D’Esposito F, Abeshi A, Ziccardi L, Falsini B, Colombo L, Iarossi G, Pilotta A, Boccone L, Guerri G, Monica M, Marta B, Maltese PE, Buzzonetti L, Rossetti L, Bertelli M. Mutation profile of BBS genes in patients with Bardet-Biedl syndrome: an Italian study. Ital J Pediatr 2019; 45:72. [PMID: 31196119 PMCID: PMC6567512 DOI: 10.1186/s13052-019-0659-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 05/16/2019] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Bardet-Biedl syndrome (BBS) is a rare inherited multisystemic disorder with autosomal recessive or complex digenic triallelic inheritance. There is currently no treatment for BBS, but some morbidities can be managed. Accurate molecular diagnosis is often crucial for the definition of appropriate patient management and for the development of a potential personalized therapy. METHODS We developed a next-generation-sequencing (NGS) protocol for the screening of the 18 most frequently mutated genes to define the genotype and clarify the mutation spectrum of a cohort of 20 BBS Italian patients. RESULTS We defined the causative variants in 60% of patients; four of those are novel. 33% of patients also harboured variants in additional gene/s, suggesting possible oligogenic inheritance. To explore the function of different genes, we looked for correlations between genotype and phenotype in our cohort. Hypogonadism was more frequently detected in patients with variants in BBSome proteins, while renal abnormalities in patients with variations in BBSome chaperonin genes. CONCLUSIONS NGS is a powerful tool that can help understanding BBS patients' phenotype through the identification of mutations that could explain differences in phenotype severity and could provide insights for the development of targeted therapy. Furthermore, our results support the existence of additional BBS loci yet to be identified.
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Affiliation(s)
| | | | - Fabiana D’Esposito
- Magi Euregio, Bolzano, Italy
- Imperial College Ophthalmic Research Unit, Western Eye Hospital, Imperial College Healthcare NHS Trust, London, UK
- Eye Clinic, Department of Neurosciences, Reproductive Sciences and Dentistry, Federico II University, Naples, Italy
| | | | | | - Benedetto Falsini
- Institute of Ophthalmology, Università Cattolica del Sacro Cuore, Rome, Italy
- Fondazione Policlinico Universitario “A. Gemelli”, IRCCS, Rome, Italy
| | - Leonardo Colombo
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy
| | - Giancarlo Iarossi
- Department of Ophthalmology, Bambino Gesù IRCCS Children’s Hospital, Rome, Italy
| | - Alba Pilotta
- Special Unit of Auxoendocrinology, Diabetology and Pediatric Genetics, University of Brescia, Spedali Civili di Brescia, Brescia, Italy
| | - Loredana Boccone
- Microcitemic Regional Hospital, Brotzu Hospital, Cagliari, Italy
| | | | - Marica Monica
- Microcitemic Regional Hospital, Brotzu Hospital, Cagliari, Italy
| | - Balzarini Marta
- Microcitemic Regional Hospital, Brotzu Hospital, Cagliari, Italy
| | | | - Luca Buzzonetti
- Department of Ophthalmology, Bambino Gesù IRCCS Children’s Hospital, Rome, Italy
| | - Luca Rossetti
- Department of Ophthalmology, San Paolo Hospital, University of Milan, Milan, Italy
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24
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Molecular genetic analysis using targeted NGS analysis of 677 individuals with retinal dystrophy. Sci Rep 2019; 9:1219. [PMID: 30718709 PMCID: PMC6362094 DOI: 10.1038/s41598-018-38007-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 12/19/2018] [Indexed: 01/29/2023] Open
Abstract
Inherited retinal diseases (IRDs) are a common cause of visual impairment. IRD covers a set of genetically highly heterogeneous disorders with more than 150 genes associated with one or more clinical forms of IRD. Molecular genetic diagnosis has become increasingly important especially due to expanding number of gene therapy strategies under development. Next generation sequencing (NGS) of gene panels has proven a valuable diagnostic tool in IRD. We present the molecular findings of 677 individuals, residing in Denmark, with IRD and report 806 variants of which 187 are novel. We found that deletions and duplications spanning one or more exons can explain 3% of the cases, and thus copy number variation (CNV) analysis is important in molecular genetic diagnostics of IRD. Seven percent of the individuals have variants classified as pathogenic or likely-pathogenic in more than one gene. Possible Danish founder variants in EYS and RP1 are reported. A significant number of variants were classified as variants with unknown significance; reporting of these will hopefully contribute to the elucidation of the actual clinical consequence making the classification less troublesome in the future. In conclusion, this study underlines the relevance of performing targeted sequencing of IRD including CNV analysis as well as the importance of interaction with clinical diagnoses.
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25
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Burkard M, Kohl S, Krätzig T, Tanimoto N, Brennenstuhl C, Bausch AE, Junger K, Reuter P, Sothilingam V, Beck SC, Huber G, Ding XQ, Mayer AK, Baumann B, Weisschuh N, Zobor D, Hahn GA, Kellner U, Venturelli S, Becirovic E, Charbel Issa P, Koenekoop RK, Rudolph G, Heckenlively J, Sieving P, Weleber RG, Hamel C, Zong X, Biel M, Lukowski R, Seeliger MW, Michalakis S, Wissinger B, Ruth P. Accessory heterozygous mutations in cone photoreceptor CNGA3 exacerbate CNG channel-associated retinopathy. J Clin Invest 2018; 128:5663-5675. [PMID: 30418171 PMCID: PMC6264655 DOI: 10.1172/jci96098] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 10/02/2018] [Indexed: 01/01/2023] Open
Abstract
Mutations in CNGA3 and CNGB3, the genes encoding the subunits of the tetrameric cone photoreceptor cyclic nucleotide-gated ion channel, cause achromatopsia, a congenital retinal disorder characterized by loss of cone function. However, a small number of patients carrying the CNGB3/c.1208G>A;p.R403Q mutation present with a variable retinal phenotype ranging from complete and incomplete achromatopsia to moderate cone dysfunction or progressive cone dystrophy. By exploring a large patient cohort and published cases, we identified 16 unrelated individuals who were homozygous or (compound-)heterozygous for the CNGB3/c.1208G>A;p.R403Q mutation. In-depth genetic and clinical analysis revealed a co-occurrence of a mutant CNGA3 allele in a high proportion of these patients (10 of 16), likely contributing to the disease phenotype. To verify these findings, we generated a Cngb3R403Q/R403Q mouse model, which was crossbred with Cnga3-deficient (Cnga3-/-) mice to obtain triallelic Cnga3+/- Cngb3R403Q/R403Q mutants. As in human subjects, there was a striking genotype-phenotype correlation, since the presence of 1 Cnga3-null allele exacerbated the cone dystrophy phenotype in Cngb3R403Q/R403Q mice. These findings strongly suggest a digenic and triallelic inheritance pattern in a subset of patients with achromatopsia/severe cone dystrophy linked to the CNGB3/p.R403Q mutation, with important implications for diagnosis, prognosis, and genetic counseling.
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Affiliation(s)
- Markus Burkard
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy
- Department of Vegetative and Clinical Physiology
| | - Susanne Kohl
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Timm Krätzig
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy
| | - Naoyuki Tanimoto
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | | | - Anne E. Bausch
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy
| | - Katrin Junger
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy
| | - Peggy Reuter
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Vithiyanjali Sothilingam
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Susanne C. Beck
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Gesine Huber
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Xi-Qin Ding
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Anja K. Mayer
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Britta Baumann
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Nicole Weisschuh
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Ditta Zobor
- Institute of Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Gesa-Astrid Hahn
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Ulrich Kellner
- Rare Retinal Disease Center, Augenzentrum Siegburg, MVZ ADTC Siegburg GmbH, Siegburg, Germany
| | | | - Elvir Becirovic
- Center for Integrated Protein Science Munich CiPSM and Department of Pharmacy–Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Peter Charbel Issa
- Oxford Eye Hospital, OUH NHS Foundation Trust and the Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom
| | - Robert K. Koenekoop
- McGill Ocular Genetics Centre, McGill University Health Centre, Montreal, Quebec, Canada
| | | | | | - Paul Sieving
- The National Eye Institute, Bethesda, Maryland, USA
| | - Richard G. Weleber
- Casey Eye Institute, Department of Ophthalmogenetics, Portland, Oregon, USA
| | - Christian Hamel
- INSERM U583, Institut des Neurosciences, Montpellier, France
| | - Xiangang Zong
- Center for Integrated Protein Science Munich CiPSM and Department of Pharmacy–Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Martin Biel
- Center for Integrated Protein Science Munich CiPSM and Department of Pharmacy–Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy
| | - Matthias W. Seeliger
- Division of Ocular Neurodegeneration, Institute for Ophthalmic Research, Centre for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Stylianos Michalakis
- Center for Integrated Protein Science Munich CiPSM and Department of Pharmacy–Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Bernd Wissinger
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, and
| | - Peter Ruth
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy
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26
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Hey CAB, Saltõkowa KB, Larsen LJ, Tümer Z, Brøndum-Nielsen K, Grønskov K, Hjortshøj TD, Møller LB. Generation of induced pluripotent stem cells, KCi002-A derived from a patient with Bardet-Biedl syndrome homozygous for the BBS10 variant c.271insT. Stem Cell Res 2018; 33:46-50. [PMID: 30312873 DOI: 10.1016/j.scr.2018.09.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 08/25/2018] [Accepted: 09/18/2018] [Indexed: 11/15/2022] Open
Abstract
Bardet-Biedl syndrome (BBS) is genetically heterogeneous with at least 21 genes involved, and BBS10 encodes, together with BBS6 and BBS12, chaperonin-like proteins which are important for the assembly of the multiprotein complex, the BBSome encoded by other BBS genes. Here we describe the successful generation of an induced pluripotent stem cell (iPSC) line KCi002-A from a male with BBS, homozygous for the disease causing variant c.271insT, p.(Cys91fsX95) in BBS10. Resource table.
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Affiliation(s)
- Caroline Amalie Brunbjerg Hey
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Katarina Beata Saltõkowa
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Lasse Jonsgaard Larsen
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Zeynep Tümer
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Karen Brøndum-Nielsen
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Karen Grønskov
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Tina Duelund Hjortshøj
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Lisbeth Birk Møller
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark.
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27
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Hey CAB, Saltõkowa KB, Larsen LJ, Tümer Z, Brøndum-Nielsen K, Grønskov K, Hjortshøj TD, Møller LB. Generation of induced pluripotent stem cells, KCi001-A derived from a Bardet-Biedl syndrome patient compound heterozygous for the BBS1 variants c.1169T>G/c.1135G>C. Stem Cell Res 2018; 31:235-239. [PMID: 30142598 DOI: 10.1016/j.scr.2018.08.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 07/19/2018] [Accepted: 08/08/2018] [Indexed: 01/13/2023] Open
Abstract
Bardet-Biedl syndrome (BBS) is an autosomal recessive ciliopathy with a wide range of symptoms including obesity, retinal dystrophy, polycystic kidney disease, polydactyly, hypogonadism and learning difficulties. Here we describe the successful generation of an induced pluripotent stem cell (iPSC) KCi001-A from a BBS patient compound heterozygous for two disease causing BBS1 variants c.1169T>G, p. (Met390Arg)/c.1135G>C, p.(Gly370Arg). Resource table.
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Affiliation(s)
- Caroline Amalie Brunbjerg Hey
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Katarina Beata Saltõkowa
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Lasse Jonsgaard Larsen
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Zeynep Tümer
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Karen Brøndum-Nielsen
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Karen Grønskov
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Tina Duelund Hjortshøj
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark
| | - Lisbeth Birk Møller
- Applied Human Molecular Genetics, Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Rigshospitalet, Gl. Landevej 7, 2600 Glostrup, Denmark.
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28
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Geets E, Meuwissen MEC, Van Hul W. Clinical, molecular genetics and therapeutic aspects of syndromic obesity. Clin Genet 2018; 95:23-40. [PMID: 29700824 DOI: 10.1111/cge.13367] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 04/05/2018] [Accepted: 04/16/2018] [Indexed: 12/13/2022]
Abstract
Obesity has become a major health problem worldwide. To date, more than 25 different syndromic forms of obesity are known in which one (monogenic) or multiple (polygenic) genes are involved. This review gives an overview of these forms and focuses more in detail on 6 syndromes: Prader Willi Syndrome and Prader Willi like phenotype, Bardet Biedl Syndrome, Alström Syndrome, Wilms tumor, Aniridia, Genitourinary malformations and mental Retardation syndrome and 16p11.2 (micro)deletions. Years of research provided plenty of information on the molecular genetics of these disorders and the obesity phenotype leading to a more individualized treatment of the symptoms, however, many questions still remain unanswered. As these obesity syndromes have different signs and symptoms in common, it makes it difficult to accurately diagnose patients which may result in inappropriate treatment of the disease. Therefore, the big challenge for clinicians and scientists is to more clearly differentiate all syndromic forms of obesity to provide conclusive genetic explanations and eventually deliver accurate genetic counseling and treatment. In addition, further delineation of the (functions of the) underlying genes with the use of array- or next-generation sequencing-based technology will be helpful to unravel the mechanisms of energy metabolism in the general population.
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Affiliation(s)
- E Geets
- Department of Medical Genetics, University of Antwerp and Antwerp University Hospital, Antwerp, Belgium
| | - M E C Meuwissen
- Department of Medical Genetics, University of Antwerp and Antwerp University Hospital, Antwerp, Belgium
| | - W Van Hul
- Department of Medical Genetics, University of Antwerp and Antwerp University Hospital, Antwerp, Belgium
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29
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Clinical characteristics of a Japanese patient with Bardet-Biedl syndrome caused by BBS10 mutations. Jpn J Ophthalmol 2018; 62:458-466. [DOI: 10.1007/s10384-018-0591-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Accepted: 03/02/2018] [Indexed: 11/26/2022]
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30
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Cytogenomic identification and long-read single molecule real-time (SMRT) sequencing of a Bardet-Biedl Syndrome 9 ( BBS9) deletion. NPJ Genom Med 2018; 3:3. [PMID: 29367880 PMCID: PMC5778042 DOI: 10.1038/s41525-017-0042-3] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 11/22/2017] [Accepted: 12/05/2017] [Indexed: 11/29/2022] Open
Abstract
Bardet–Biedl syndrome (BBS) is a recessive disorder characterized by heterogeneous clinical manifestations, including truncal obesity, rod-cone dystrophy, renal anomalies, postaxial polydactyly, and variable developmental delays. At least 20 genes have been implicated in BBS, and all are involved in primary cilia function. We report a 1-year-old male child from Guyana with obesity, postaxial polydactyly on his right foot, hypotonia, ophthalmologic abnormalities, and developmental delay, which together indicated a clinical diagnosis of BBS. Clinical chromosomal microarray (CMA) testing and high-throughput BBS gene panel sequencing detected a homozygous 7p14.3 deletion of exons 1–4 of BBS9 that was encompassed by a 17.5 Mb region of homozygosity at chromosome 7p14.2–p21.1. The precise breakpoints of the deletion were delineated to a 72.8 kb region in the proband and carrier parents by third-generation long-read single molecule real-time (SMRT) sequencing (Pacific Biosciences), which suggested non-homologous end joining as a likely mechanism of formation. Long-read SMRT sequencing of the deletion breakpoints also determined that the aberration included the neighboring RP9 gene implicated in retinitis pigmentosa; however, the clinical significance of this was considered uncertain given the paucity of reported cases with unambiguous RP9 mutations. Taken together, our study characterized a BBS9 deletion, and the identification of this shared haplotype in the parents suggests that this pathogenic aberration may be a BBS founder mutation in the Guyanese population. Importantly, this informative case also highlights the utility of long-read SMRT sequencing to map nucleotide breakpoints of clinically relevant structural variants.
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31
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Álvarez-Satta M, Castro-Sánchez S, Valverde D. Bardet-Biedl Syndrome as a Chaperonopathy: Dissecting the Major Role of Chaperonin-Like BBS Proteins (BBS6-BBS10-BBS12). Front Mol Biosci 2017; 4:55. [PMID: 28824921 PMCID: PMC5534436 DOI: 10.3389/fmolb.2017.00055] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 07/13/2017] [Indexed: 01/01/2023] Open
Abstract
Bardet-Biedl syndrome (BBS) is a rare genetic disorder that belongs to the group of ciliopathies, defined as diseases caused by defects in cilia structure and/or function. The six diagnostic features considered for this syndrome include retinal dystrophy, obesity, polydactyly, cognitive impairment and renal and urogenital anomalies. Furthermore, three of the 21 genes currently known to be involved in BBS encode chaperonin-like proteins (MKKS/BBS6, BBS10, and BBS12), so BBS can be also considered a member of the growing group of chaperonopathies. Remarkably, up to 50% of clinically-diagnosed BBS families can harbor disease-causing variants in these three genes, which highlights the importance of chaperone defects as pathogenic factors even for genetically heterogeneous syndromes such as BBS. In addition, it is interesting to note that BBS families with deleterious variants in MKKS/BBS6, BBS10 or BBS12 genes generally display more severe phenotypes than families with changes in other BBS genes. The chaperonin-like BBS proteins have structural homology to the CCT family of group II chaperonins, although they are believed to conserve neither the ATP-dependent folding activity of canonical CCT chaperonins nor the ability to form CCT-like oligomeric complexes. Thus, they play an important role in the initial steps of assembly of the BBSome, which is a multiprotein complex essential for mediating the ciliary trafficking activity. In this review, we present a comprehensive review of those genetic, functional and evolutionary aspects concerning chaperonin-like BBS proteins, trying to provide a new perspective that expands the classical conception of BBS only from a ciliary point of view.
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Affiliation(s)
- María Álvarez-Satta
- Grupo de Biomarcadores Moleculares, Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de VigoVigo, Spain.,Grupo de Investigación en Enfermedades Raras y Medicina Pediátrica, Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), SERGAS-UVIGOVigo, Spain.,Centro de Investigaciones Biomédicas (Centro Singular de Investigación de Galicia 2016-2019), Universidad de VigoVigo, Spain
| | - Sheila Castro-Sánchez
- Grupo de Biomarcadores Moleculares, Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de VigoVigo, Spain.,Grupo de Investigación en Enfermedades Raras y Medicina Pediátrica, Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), SERGAS-UVIGOVigo, Spain.,Centro de Investigaciones Biomédicas (Centro Singular de Investigación de Galicia 2016-2019), Universidad de VigoVigo, Spain
| | - Diana Valverde
- Grupo de Biomarcadores Moleculares, Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de VigoVigo, Spain.,Grupo de Investigación en Enfermedades Raras y Medicina Pediátrica, Instituto de Investigación Sanitaria Galicia Sur (IIS Galicia Sur), SERGAS-UVIGOVigo, Spain.,Centro de Investigaciones Biomédicas (Centro Singular de Investigación de Galicia 2016-2019), Universidad de VigoVigo, Spain
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Abstract
Bardet-Biedl syndrome (BBS) is a rare autosomal recessive genetic disorder. It is characterized by heterogeneous clinical manifestations including primary features of the disease (rod-cone dystrophy, polydactyly, obesity, genital abnormalities, renal defects, and learning difficulties) and secondary BBS characteristics (developmental delay, speech deficit, brachydactyly or syndactyly, dental defects, ataxia or poor coordination, olfactory deficit, diabetes mellitus, congenital heart disease, etc.); most of these symptoms may not be present at birth but appear and progressively worsen during the first and second decades of life. At least 20 BBS genes have already been identified, and all of them are involved in primary cilia functioning. Genetic diagnosis of BBS is complicated due to lack of gene-specific disease symptoms; however, it is gradually becoming more accessible with the invention of multigene sequencing technologies. Clinical management of BBS is largely limited to a symptomatic treatment. Mouse experiments demonstrate that the most debilitating complication of BBS, blindness, can be rescued by topical gene therapy. There is a published case report describing the delay of BBS symptoms by nutritional compensation of the disease-related biochemical deficiencies. Progress in DNA testing technologies is likely to rapidly resolve all limitations in BBS diagnosis; however, much slower improvement is expected with regard to BBS treatment.
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Affiliation(s)
- Evgeny N Suspitsin
- N.N. Petrov Institute of Oncology, St. Petersburg, Russia; St. Petersburg Pediatric Medical University, St. Petersburg, Russia
| | - Evgeny N Imyanitov
- N.N. Petrov Institute of Oncology, St. Petersburg, Russia; St. Petersburg Pediatric Medical University, St. Petersburg, Russia; I.I. Mechnikov North-Western Medical University, St. Petersburg, Russia; St. Petersburg State University, St. Petersburg, Russia
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33
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Khan S, Muhammad N, Khan M, Kamal A, Rehman Z, Khan S. Genetics of human Bardet-Biedl syndrome, an updates. Clin Genet 2016; 90:3-15. [DOI: 10.1111/cge.12737] [Citation(s) in RCA: 98] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Revised: 12/21/2015] [Accepted: 01/03/2016] [Indexed: 12/22/2022]
Affiliation(s)
- S.A. Khan
- Department of Biotechnology and Genetic Engineering; Kohat University of Science and Technology; Khyber Pakhtunkhwa Pakistan
| | - N. Muhammad
- Department of Biotechnology and Genetic Engineering; Kohat University of Science and Technology; Khyber Pakhtunkhwa Pakistan
| | - M.A. Khan
- Gomal Centre of Biochemistry and Biotechnology; Gomal University; Khyber Pakhtunkhwa Pakistan
- Genomic Core Facility; Interim Translational Research Institute; Doha Qatar
| | - A. Kamal
- Department of Biotechnology and Genetic Engineering; Kohat University of Science and Technology; Khyber Pakhtunkhwa Pakistan
| | - Z.U. Rehman
- Department of Biotechnology and Genetic Engineering; Kohat University of Science and Technology; Khyber Pakhtunkhwa Pakistan
| | - S. Khan
- Department of Biotechnology and Genetic Engineering; Kohat University of Science and Technology; Khyber Pakhtunkhwa Pakistan
- Genomic Core Facility; Interim Translational Research Institute; Doha Qatar
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34
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[Algorithm for the molecular analysis of Bardet-Biedl syndrome in Spain]. Med Clin (Barc) 2015; 145:147-52. [PMID: 25087209 DOI: 10.1016/j.medcli.2014.05.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 05/07/2014] [Accepted: 05/08/2014] [Indexed: 11/23/2022]
Abstract
BACKGROUND AND OBJECTIVE Bardet-Biedl syndrome (BBS) is a multisystemic genetic disorder, which is not widespread among the Caucasian population, characterized by a highly variable phenotype and great genetic heterogeneity. BBS belongs to a group of diseases called ciliopathies, caused by defects in the structure and/or function of cilia. Due to the diagnostic complexity of the syndrome, the objective of this study was to analyse our whole group of patients in order to create an algorithm to facilitate the routine molecular diagnosis of BBS. We also calculated several epidemiological parameters in our cohort. PATIENTS AND METHOD We analysed 116 BBS patients belonging to 89 families from the whole Spanish geography. All probands fulfilled diagnosis criteria established for BBS. For this, we used: genotyping microarray, direct sequencing and homozygosis mapping (in consanguineous families). RESULTS By means of the different approaches, it was possible to diagnose 47% of families (21% by genotyping microarray, 18% by direct sequencing of predominant BBS genes, and 8% by homozygosis mapping). With regard to epidemiological data, a prevalence value of 1:407,000 was obtained for BBS in Spain, and a sex ratio of 1.4:1 (men:women). CONCLUSIONS The proposed algorithm, based on the analysis of predominant BBS genes combined with homozygosis mapping, allowed us to confirm the molecular diagnosis in a significant percentage of families with clinically suspected BBS. This diagnostic algorithm will be useful for the improvement of the efficiency of molecular analysis in BBS.
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Castro-Sánchez S, Álvarez-Satta M, Cortón M, Guillén E, Ayuso C, Valverde D. Exploring genotype-phenotype relationships in Bardet-Biedl syndrome families. J Med Genet 2015; 52:503-13. [PMID: 26082521 DOI: 10.1136/jmedgenet-2015-103099] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 05/26/2015] [Indexed: 11/03/2022]
Abstract
BACKGROUND Bardet-Biedl syndrome (BBS) is a pleiotropic autosomal recessive ciliopathy that displays retinal dystrophy, obesity, polydactyly, cognitive impairment, urogenital anomalies and renal abnormalities as primary clinical features. To date, 19 causative genes (BBS1-19) have been involved, whose mutations would explain over 80% of patients. The overlapping phenotypes among ciliopathies, in addition to the high intrafamilial and interfamilial variability in clinical presentation, further complicate the diagnosis of this syndrome. Thus, the main purpose of this study was to elucidate some genotype-phenotype trends that could be helpful to focus the molecular diagnosis of patients with BBS. METHODS Thirty-seven families (52 cases) with mutations in BBS1 or chaperonin-like BBS genes (BBS6, BBS10, BBS12) from our Spanish cohort were enrolled. Systemic and ocular features were documented as comprehensively as possible. RESULTS Comparing BBS1 versus chaperonin-like genes phenotypes we found more severe clinical features in the second group, since they displayed higher prevalence of all primary features, remarkable being the frequency of cognitive impairment (75%) in BBS12 and urogenital anomalies (83%) in patients with BBS10. With regards to p.(Met390Arg) cases, homozygotes showed a relatively more severe ocular phenotype than compound heterozygotes, since more severe fundus alterations and higher frequency of cataracts and dyschromatopsia (not previously described) were documented in the first group. The phenotypes observed frequently overlapped with Alström syndrome and, in the case of chaperonin-like genes, McKusick-Kauffman syndrome overlapping was detected. CONCLUSIONS We provide the first evidence of BBS12 mutations related to severe phenotypes as previously described for patients with BBS10, while BBS1 ocular phenotype should not be considered as mild as generally reported when compared with other BBS phenotypes.
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Affiliation(s)
- Sheila Castro-Sánchez
- Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, Vigo, Spain Instituto de Investigación Biomédica Ourense-Pontevedra-Vigo (IBI), Vigo, Spain
| | - María Álvarez-Satta
- Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, Vigo, Spain Instituto de Investigación Biomédica Ourense-Pontevedra-Vigo (IBI), Vigo, Spain
| | - Marta Cortón
- Department of Genetics, IIS-Fundación Jiménez Díaz, CIBERER, Madrid, Spain
| | - Encarna Guillén
- Medical Genetics Unit, Pediatrics Service, Virgen de la Arrixaca University Hospital, Murcia, Spain
| | - Carmen Ayuso
- Department of Genetics, IIS-Fundación Jiménez Díaz, CIBERER, Madrid, Spain
| | - Diana Valverde
- Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, Vigo, Spain Instituto de Investigación Biomédica Ourense-Pontevedra-Vigo (IBI), Vigo, Spain
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Mutation profile of BBS genes in Iranian patients with Bardet–Biedl syndrome: genetic characterization and report of nine novel mutations in five BBS genes. J Hum Genet 2014; 59:368-75. [DOI: 10.1038/jhg.2014.28] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 02/14/2014] [Accepted: 04/01/2014] [Indexed: 02/07/2023]
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Forsythe E, Sparks K, Hoskins BE, Bagkeris E, McGowan BM, Carroll PV, Huda MSB, Mujahid S, Peters C, Barrett T, Mohammed S, Beales PL. Genetic predictors of cardiovascular morbidity in Bardet-Biedl syndrome. Clin Genet 2014; 87:343-9. [PMID: 24611735 PMCID: PMC4402025 DOI: 10.1111/cge.12373] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 03/04/2014] [Accepted: 03/04/2014] [Indexed: 01/27/2023]
Abstract
Bardet-Biedl syndrome is a rare ciliopathy characterized by retinal dystrophy, obesity, intellectual disability, polydactyly, hypogonadism and renal impairment. Patients are at high risk of cardiovascular disease. Mutations in BBS1 and BBS10 account for more than half of those with molecular confirmation of the diagnosis. To elucidate genotype-phenotype correlations with respect to cardiovascular risk indicators 50 patients with mutations in BBS1 were compared with 19 patients harbouring BBS10 mutations. All patients had truncating, missense or compound missense/truncating mutations. The effect of genotype and mutation type was analysed. C-reactive protein was higher in those with mutations in BBS10 and homozygous truncating mutations (p = 0.013 and p = 0.002, respectively). Patients with mutations in BBS10 had higher levels of C peptide than those with mutations in BBS1 (p = 0.043). Triglyceride levels were significantly elevated in patients with homozygous truncating mutations (p = 0.048). Gamma glutamyl transferase was higher in patients with homozygous truncating mutations (p = 0.007) and heterozygous missense and truncating mutations (p = 0.002) than those with homozygous missense mutations. The results are compared with clinical cardiovascular risk factors. Patients with missense mutations in BBS1 have lower biochemical cardiovascular disease markers compared with patients with BBS10 and other BBS1 mutations. This could contribute to stratification of the clinical service.
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Affiliation(s)
- E Forsythe
- Molecular Medicine Unit, UCL Institute of Child Health, University College London, London, UK
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Drosophila models of early onset cognitive disorders and their clinical applications. Neurosci Biobehav Rev 2014; 46 Pt 2:326-42. [PMID: 24661984 DOI: 10.1016/j.neubiorev.2014.01.013] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 01/28/2014] [Accepted: 01/31/2014] [Indexed: 12/28/2022]
Abstract
The number of genes known to cause human monogenic diseases is increasing rapidly. For the extremely large, genetically and phenotypically heterogeneous group of intellectual disability (ID) disorders, more than 600 causative genes have been identified to date. However, knowledge about the molecular mechanisms and networks disrupted by these genetic aberrations is lagging behind. The fruit fly Drosophila has emerged as a powerful model organism to close this knowledge gap. This review summarizes recent achievements that have been made in this model and envisions its future contribution to our understanding of ID genetics and neuropathology. The available resources and efficiency of Drosophila place it in a position to tackle the main challenges in the field: mapping functional modules of ID genes to provide conceptually novel insights into the genetic control of cognition, tailored functional studies to improve 'next-generation' diagnostics, and identification of reversible ID phenotypes and medication. Drosophila's behavioral repertoire and powerful genetics also open up perspectives for modeling genetically complex forms of ID and neuropsychiatric disorders, which overlap in their genetic etiologies. In conclusion, Drosophila provides many opportunities to advance future medical genomics of early onset cognitive disorders.
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de Castro-Miró M, Pomares E, Lorés-Motta L, Tonda R, Dopazo J, Marfany G, Gonzàlez-Duarte R. Combined genetic and high-throughput strategies for molecular diagnosis of inherited retinal dystrophies. PLoS One 2014; 9:e88410. [PMID: 24516651 PMCID: PMC3917917 DOI: 10.1371/journal.pone.0088410] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 01/06/2014] [Indexed: 12/30/2022] Open
Abstract
Most diagnostic laboratories are confronted with the increasing demand for molecular diagnosis from patients and families and the ever-increasing genetic heterogeneity of visual disorders. Concerning Retinal Dystrophies (RD), almost 200 causative genes have been reported to date, and most families carry private mutations. We aimed to approach RD genetic diagnosis using all the available genetic information to prioritize candidates for mutational screening, and then restrict the number of cases to be analyzed by massive sequencing. We constructed and optimized a comprehensive cosegregation RD-chip based on SNP genotyping and haplotype analysis. The RD-chip allows to genotype 768 selected SNPs (closely linked to 100 RD causative genes) in a single cost-, time-effective step. Full diagnosis was attained in 17/36 Spanish pedigrees, yielding 12 new and 12 previously reported mutations in 9 RD genes. The most frequently mutated genes were USH2A and CRB1. Notably, RD3–up to now only associated to Leber Congenital Amaurosis– was identified as causative of Retinitis Pigmentosa. The main assets of the RD-chip are: i) the robustness of the genetic information that underscores the most probable candidates, ii) the invaluable clues in cases of shared haplotypes, which are indicative of a common founder effect, and iii) the detection of extended haplotypes over closely mapping genes, which substantiates cosegregation, although the assumptions in which the genetic analysis is based could exceptionally lead astray. The combination of the genetic approach with whole exome sequencing (WES) greatly increases the diagnosis efficiency, and revealed novel mutations in USH2A and GUCY2D. Overall, the RD-chip diagnosis efficiency ranges from 16% in dominant, to 80% in consanguineous recessive pedigrees, with an average of 47%, well within the upper range of massive sequencing approaches, highlighting the validity of this time- and cost-effective approach whilst high-throughput methodologies become amenable for routine diagnosis in medium sized labs.
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Affiliation(s)
- Marta de Castro-Miró
- Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
- Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Esther Pomares
- Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
| | - Laura Lorés-Motta
- Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Raul Tonda
- Centre Nacional d’Anàlisi Genòmica, PCB, Barcelona, Spain
| | - Joaquín Dopazo
- Department of Computational Genomics, Centro de Investigación Príncipe Felipe, Valencia, Spain
- BIER, Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Valencia, Spain
| | - Gemma Marfany
- Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
- Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
| | - Roser Gonzàlez-Duarte
- Departament de Genètica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, Barcelona, Spain
- Institut de Biomedicina (IBUB), Universitat de Barcelona, Barcelona, Spain
- * E-mail:
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Álvarez-Satta M, Castro-Sánchez S, Pereiro I, Piñeiro-Gallego T, Baiget M, Ayuso C, Valverde D. Overview of Bardet-Biedl syndrome in Spain: identification of novel mutations in BBS1, BBS10 and BBS12 genes. Clin Genet 2014; 86:601-2. [PMID: 24611592 DOI: 10.1111/cge.12334] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 12/13/2013] [Accepted: 12/17/2013] [Indexed: 11/27/2022]
Affiliation(s)
- M Álvarez-Satta
- Departamento de Bioquímica, Genética e Inmunología, Facultad de Biología, Universidad de Vigo, Vigo, Spain
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M'hamdi O, Ouertani I, Chaabouni-Bouhamed H. Update on the genetics of bardet-biedl syndrome. Mol Syndromol 2013; 5:51-6. [PMID: 24715851 DOI: 10.1159/000357054] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2013] [Indexed: 12/18/2022] Open
Abstract
Bardet-Biedl syndrome (BBS) is an autosomal recessive disease characterized by retinal dystrophy, obesity, postaxial polydactyly, learning disabilities, renal involvement, and male hypogenitalism. BBS is genetically heterogeneous, and to date 18 genes (BBS1-18) have been described. Mutations in known BBS genes account for approximately 70-80% of cases, and triallelic inheritance has been suggested in about 5%. Many minor features can be helpful in making the clinical diagnosis. Recently, the use of next-generation sequencing technologies has accelerated the identification of novel genes and causative disease mutations in known genes. This report presents a concise overview of the current knowledge on clinical data in BBS and the progress in molecular genetics research. A future objective will be the development of BBS diagnosis kits in order to offer genetic counseling for families at risk.
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Affiliation(s)
- O M'hamdi
- Department of Human Genetics, Faculty of Medicine, Tunis El-Manar University, Tunis, Tunisia
| | - I Ouertani
- Department of Human Genetics, Faculty of Medicine, Tunis El-Manar University, Tunis, Tunisia ; Department of Hereditary and Congenital Disorders, Charles Nicolle Hospital, Tunis, Tunisia
| | - H Chaabouni-Bouhamed
- Department of Human Genetics, Faculty of Medicine, Tunis El-Manar University, Tunis, Tunisia ; Department of Hereditary and Congenital Disorders, Charles Nicolle Hospital, Tunis, Tunisia
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Koefoed K, Veland IR, Pedersen LB, Larsen LA, Christensen ST. Cilia and coordination of signaling networks during heart development. Organogenesis 2013; 10:108-25. [PMID: 24345806 DOI: 10.4161/org.27483] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Primary cilia are unique sensory organelles that coordinate a wide variety of different signaling pathways to control cellular processes during development and in tissue homeostasis. Defects in function or assembly of these antenna-like structures are therefore associated with a broad range of developmental disorders and diseases called ciliopathies. Recent studies have indicated a major role of different populations of cilia, including nodal and cardiac primary cilia, in coordinating heart development, and defects in these cilia are associated with congenital heart disease. Here, we present an overview of the role of nodal and cardiac primary cilia in heart development.
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Affiliation(s)
- Karen Koefoed
- Department of Biology; University of Copenhagen; Copenhagen, Denmark; Wilhelm Johannsen Centre for Functional Genome Research; Department of Cellular and Molecular Medicine; University of Copenhagen; Copenhagen, Denmark
| | - Iben Rønn Veland
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
| | | | - Lars Allan Larsen
- Wilhelm Johannsen Centre for Functional Genome Research; Department of Cellular and Molecular Medicine; University of Copenhagen; Copenhagen, Denmark
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González-Del Pozo M, Méndez-Vidal C, Santoyo-Lopez J, Vela-Boza A, Bravo-Gil N, Rueda A, García-Alonso L, Vázquez-Marouschek C, Dopazo J, Borrego S, Antiñolo G. Deciphering intrafamilial phenotypic variability by exome sequencing in a Bardet-Biedl family. Mol Genet Genomic Med 2013; 2:124-33. [PMID: 24689075 PMCID: PMC3960054 DOI: 10.1002/mgg3.50] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 10/09/2013] [Accepted: 10/16/2013] [Indexed: 12/15/2022] Open
Abstract
Bardet-Biedl syndrome (BBS) is a model ciliopathy characterized by a wide range of clinical variability. The heterogeneity of this condition is reflected in the number of underlying gene defects and the epistatic interactions between the proteins encoded. BBS is generally inherited in an autosomal recessive trait. However, in some families, mutations across different loci interact to modulate the expressivity of the phenotype. In order to investigate the magnitude of epistasis in one BBS family with remarkable intrafamilial phenotypic variability, we designed an exome sequencing-based approach using SOLID 5500xl platform. This strategy allowed the reliable detection of the primary causal mutations in our family consisting of two novel compound heterozygous mutations in McKusick-Kaufman syndrome (MKKS) gene (p.D90G and p.V396F). Additionally, exome sequencing enabled the detection of one novel heterozygous NPHP4 variant which is predicted to activate a cryptic acceptor splice site and is only present in the most severely affected patient. Here, we provide an exome sequencing analysis of a BBS family and show the potential utility of this tool, in combination with network analysis, to detect disease-causing mutations and second-site modifiers. Our data demonstrate how next-generation sequencing (NGS) can facilitate the dissection of epistatic phenomena, and shed light on the genetic basis of phenotypic variability.
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Affiliation(s)
- María González-Del Pozo
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocio/Consejo Superior de Investigaciones Científicas/University of Seville Seville, Spain ; Centre for Biomedical Network Research on Rare Diseases (CIBERER) Seville, Spain
| | - Cristina Méndez-Vidal
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocio/Consejo Superior de Investigaciones Científicas/University of Seville Seville, Spain ; Centre for Biomedical Network Research on Rare Diseases (CIBERER) Seville, Spain
| | - Javier Santoyo-Lopez
- Medical Genome Project, Genomics and Bioinformatics Platform of Andalusia (GBPA) Seville, Spain
| | - Alicia Vela-Boza
- Medical Genome Project, Genomics and Bioinformatics Platform of Andalusia (GBPA) Seville, Spain
| | - Nereida Bravo-Gil
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocio/Consejo Superior de Investigaciones Científicas/University of Seville Seville, Spain
| | - Antonio Rueda
- Medical Genome Project, Genomics and Bioinformatics Platform of Andalusia (GBPA) Seville, Spain
| | - Luz García-Alonso
- Department of Computational Genomics, Centro de Investigación Príncipe Felipe (CIPF) Valencia, Spain
| | | | - Joaquín Dopazo
- Medical Genome Project, Genomics and Bioinformatics Platform of Andalusia (GBPA) Seville, Spain ; Department of Computational Genomics, Centro de Investigación Príncipe Felipe (CIPF) Valencia, Spain ; Functional Genomics Node (INB), CIPF Valencia, Spain
| | - Salud Borrego
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocio/Consejo Superior de Investigaciones Científicas/University of Seville Seville, Spain ; Centre for Biomedical Network Research on Rare Diseases (CIBERER) Seville, Spain
| | - Guillermo Antiñolo
- Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocio/Consejo Superior de Investigaciones Científicas/University of Seville Seville, Spain ; Centre for Biomedical Network Research on Rare Diseases (CIBERER) Seville, Spain ; Medical Genome Project, Genomics and Bioinformatics Platform of Andalusia (GBPA) Seville, Spain
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Abstract
Digenic inheritance (DI) is the simplest form of inheritance for genetically complex diseases. By contrast with the thousands of reports that mutations in single genes cause human diseases, there are only dozens of human disease phenotypes with evidence for DI in some pedigrees. The advent of high-throughput sequencing (HTS) has made it simpler to identify monogenic disease causes and could similarly simplify proving DI because one can simultaneously find mutations in two genes in the same sample. However, through 2012, I could find only one example of human DI in which HTS was used; in that example, HTS found only the second of the two genes. To explore the gap between expectation and reality, I tried to collect all examples of human DI with a narrow definition and characterise them according to the types of evidence collected, and whether there has been replication. Two strong trends are that knowledge of candidate genes and knowledge of protein–protein interactions (PPIs) have been helpful in most published examples of human DI. By contrast, the positional method of genetic linkage analysis, has been mostly unsuccessful in identifying genes underlying human DI. Based on the empirical data, I suggest that combining HTS with growing networks of established PPIs may expedite future discoveries of human DI and strengthen the evidence for them.
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M'hamdi O, Redin C, Stoetzel C, Ouertani I, Chaabouni M, Maazoul F, M'rad R, Mandel JL, Dollfus H, Muller J, Chaabouni H. Clinical and genetic characterization of Bardet-Biedl syndrome in Tunisia: defining a strategy for molecular diagnosis. Clin Genet 2013; 85:172-7. [PMID: 23432027 DOI: 10.1111/cge.12129] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 02/18/2013] [Accepted: 02/18/2013] [Indexed: 01/11/2023]
Abstract
Bardet-Biedl syndrome (BBS, OMIM 209900) is a rare genetic disorder characterized by obesity, retinitis pigmentosa, post axial polydactyly, cognitive impairment, renal anomalies and hypogonadism. The aim of this study is to provide a comprehensive clinical and molecular analysis of a cohort of 11 Tunisian BBS consanguineous families in order to give insight into clinical and genetic spectrum and the genotype-phenotype correlations. Molecular analysis using combined sequence capture and high-throughput sequencing of 30 ciliopathies genes revealed 11 mutations in 11 studied families. Five mutations were novel and six were previously described. Novel mutations included c.1110G>A and c.39delA (p.G13fs*41) in BBS1, c.115+5G>A in BBS2, c.1272+1G>A in BBS6, c.1181_1182insGCATTTATACC in BBS10 (p.S396Lfs*6). Described mutations included c.436C>T (p.R146*) and c.1473+4A>G in BBS1, c.565C> (p.R189*) in BBS2, deletion of exons 4-6 in BBS4, c.149T>G (p.L50R) in BBS5, and c.459+1G>A in BBS8; most frequent mutations were described in BBS1 (4/11, 37%) and BBS2 (2/11, 18%) genes. No phenotype-genotype correlation was evidenced. This data expands the mutations profile of BBS genes in Tunisia and suggests a divergence of the genetic spectrum comparing Tunisian and other populations.
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Affiliation(s)
- O M'hamdi
- Faculté de médecine de Tunis, Université de Tunis El-Manar, Tunis, Tunisie
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Khan S, Ullah I, Irfanullah, Touseef M, Basit S, Khan MN, Ahmad W. Novel homozygous mutations in the genes ARL6 and BBS10 underlying Bardet-Biedl syndrome. Gene 2012; 515:84-8. [PMID: 23219996 DOI: 10.1016/j.gene.2012.11.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 10/21/2012] [Accepted: 11/27/2012] [Indexed: 12/29/2022]
Abstract
Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder resulting from structural and functional defects in numerous organs. Frequent manifestations reported in the syndrome include obesity, renal dysplasia, cognitive impairment, postaxial polydactyly, pigmentary retinal degeneration and hypogonadism. To date, 17 genes causing BBS have been identified. Two of these BBS1 and BBS10 are the most frequently mutated genes. The present report describes two consanguineous families (A, B) with clinical manifestations of BBS. Linkage in the family A was established to ARL6 on chromosome 3q11.2, while family B showed linkage to BBS10 on chromosome 12q21.2. Sequence analysis revealed a novel homozygous missense mutation (c.281T>C, p.Ile94Thr) in the gene ARL6 in family A and a nonsense mutation (c.1075C>T, p.Gln359*) in the gene BBS10 in family B. Mutations identified in the present study extend the body of evidence implicating the genes ARL6 and BBS10 in causing Bardet-Biedl syndrome.
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Affiliation(s)
- Saadullah Khan
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University Islamabad, Pakistan
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47
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Abstract
Bardet-Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy characterised by retinal dystrophy, obesity, post-axial polydactyly, renal dysfunction, learning difficulties and hypogonadism. Many associated minor features can be helpful in making a diagnosis and are important in the clinical management of BBS. The diagnosis is based on clinical findings and can be confirmed by sequencing of known disease-causing genes in 80% of patients. BBS genes encode proteins that localise to the cilia and basal body and are involved in cilia biogenesis and function. Mutations lead to defective cilia accounting in part for the pleiotropic effects observed in BBS. We provide an overview of BBS including the clinical findings, current understanding of cilia biology, and a practical approach to diagnosis, genetic counselling and up-to-date management.
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Affiliation(s)
- Elizabeth Forsythe
- Molecular Medicine Unit, Institute of Child Health, University College London, London, UK
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Putoux A, Attie-Bitach T, Martinovic J, Gubler MC. Phenotypic variability of Bardet-Biedl syndrome: focusing on the kidney. Pediatr Nephrol 2012; 27:7-15. [PMID: 21246219 DOI: 10.1007/s00467-010-1751-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Revised: 11/26/2010] [Accepted: 11/30/2010] [Indexed: 12/12/2022]
Abstract
Bardet-Biedl syndrome (BBS) is a multisystemic developmental disorder diagnosed on the basis of the presence of obesity, retinal defects, polydactyly, hypogonadism, renal dysfunction, and learning disabilities. The syndrome is genetically heterogeneous with 14 BBS genes identified to date. Since the cloning of the first gene in 2000, a combination of genetic, in vitro, and in vivo studies have highlighted ciliary dysfunction as a primary cause of BBS pathology. Pleiotropy of ciliopathy phenotypes and complex genetic interactions between causal and modifying alleles of ciliary genes contribute to phenotypic variability. In particular, kidney disease in BBS is clinically heterogeneous, but is now recognized as a cardinal feature and a major cause of mortality in BBS.
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Affiliation(s)
- Audrey Putoux
- INSERM U-781, Hôpital Necker-Enfants Malades, Paris, France
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Chen J, Smaoui N, Hammer MBH, Jiao X, Riazuddin SA, Harper S, Katsanis N, Riazuddin S, Chaabouni H, Berson EL, Hejtmancik JF. Molecular analysis of Bardet-Biedl syndrome families: report of 21 novel mutations in 10 genes. Invest Ophthalmol Vis Sci 2011; 52:5317-24. [PMID: 21642631 DOI: 10.1167/iovs.11-7554] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Bardet-Biedl syndrome (BBS) is genetically heterogeneous with 15 BBS genes currently identified, accounting for approximately 70% of cases. The aim of our study was to define further the spectrum of BBS mutations in a cohort of 44 European-derived American, 8 Tunisian, 1 Arabic, and 2 Pakistani families (55 families in total) with BBS. METHODS A total of 142 exons of the first 12 BBS-causing genes were screened by dideoxy sequencing. Cases in which no mutations were found were then screened for BBS13, BBS14, BBS15, RPGRIP1L, CC2D2A, NPHP3, TMEM67, and INPP5E. RESULTS Forty-three mutations, including 8 frameshift mutations, 10 nonsense mutations, 4 splice site mutations, 1 deletion, and 20 potentially or probably pathogenic missense variations, were identified in 46 of the 55 families studied (84%). Of these, 21 (2 frameshift mutations, 4 nonsense mutations, 4 splice site mutations, 1 deletion, and 10 missense variations) were novel. The molecular genetic findings raised the possibility of triallelic inheritance in 7 Caucasian families, 1 Arabian family, and 1 Tunisian patient. No mutations were detected for BBS4, BBS11, BBS13, BBS14, BBS15, RPGRIP1L, CC2D2A, NPHP3, TMEM67, or INPP5E. CONCLUSIONS This mutational analysis extends the spectrum of known BBS mutations. Identification of 21 novel mutations highlights the genetic heterogeneity of this disorder. Differences in European and Tunisian patients, including the high frequency of the M390R mutation in Europeans, emphasize the population specificity of BBS mutations with potential diagnostic implications. The existence of some BBS cases without mutations in any currently identified BBS genes suggests further genetic heterogeneity.
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Affiliation(s)
- Jianjun Chen
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20852, USA
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