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Corradi Z, Dhaenens CM, Grunewald O, Kocabaş IS, Meunier I, Banfi S, Karali M, Cremers FPM, Hitti-Malin RJ. Novel and Recurrent Copy Number Variants in ABCA4-Associated Retinopathy. Int J Mol Sci 2024; 25:5940. [PMID: 38892127 PMCID: PMC11173210 DOI: 10.3390/ijms25115940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 05/22/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024] Open
Abstract
ABCA4 is the most frequently mutated gene leading to inherited retinal disease (IRD) with over 2200 pathogenic variants reported to date. Of these, ~1% are copy number variants (CNVs) involving the deletion or duplication of genomic regions, typically >50 nucleotides in length. An in-depth assessment of the current literature based on the public database LOVD, regarding the presence of known CNVs and structural variants in ABCA4, and additional sequencing analysis of ABCA4 using single-molecule Molecular Inversion Probes (smMIPs) for 148 probands highlighted recurrent and novel CNVs associated with ABCA4-associated retinopathies. An analysis of the coverage depth in the sequencing data led to the identification of eleven deletions (six novel and five recurrent), three duplications (one novel and two recurrent) and one complex CNV. Of particular interest was the identification of a complex defect, i.e., a 15.3 kb duplicated segment encompassing exon 31 through intron 41 that was inserted at the junction of a downstream 2.7 kb deletion encompassing intron 44 through intron 47. In addition, we identified a 7.0 kb tandem duplication of intron 1 in three cases. The identification of CNVs in ABCA4 can provide patients and their families with a genetic diagnosis whilst expanding our understanding of the complexity of diseases caused by ABCA4 variants.
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Affiliation(s)
- Zelia Corradi
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Claire-Marie Dhaenens
- Université de Lille, Inserm, CHU Lille, U1172-LilNCog-Lille Neuroscience & Cognition, F-59000 Lille, France
| | - Olivier Grunewald
- Université de Lille, Inserm, CHU Lille, U1172-LilNCog-Lille Neuroscience & Cognition, F-59000 Lille, France
| | - Ipek Selen Kocabaş
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Isabelle Meunier
- Institute des Neurosciences de Montpellier, INSERM, Université de Montpellier, F-34295 Montpellier, France
| | - Sandro Banfi
- Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, 81031 Naples, Italy
- Telethon Institute of Genetics and Medicine (TIGEM), 80078 Pozzuoli, Italy
| | - Marianthi Karali
- Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, 81031 Naples, Italy
- Eye Clinic, Multidisciplinary Department of Medical, Surgical and Dental Sciences, University of Campania “Luigi Vanvitelli”, 81031 Naples, Italy
| | - Frans P. M. Cremers
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Rebekkah J. Hitti-Malin
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
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2
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Kaltak M, Blanco-Garavito R, Molday LL, Dhaenens CM, Souied EE, Platenburg G, Swildens J, Molday RS, Cremers FPM. Stargardt disease-associated in-frame ABCA4 exon 17 skipping results in significant ABCA4 function. J Transl Med 2023; 21:546. [PMID: 37587475 PMCID: PMC10428568 DOI: 10.1186/s12967-023-04406-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 08/01/2023] [Indexed: 08/18/2023] Open
Abstract
BACKGROUND ABCA4, the gene implicated in Stargardt disease (STGD1), contains 50 exons, of which 17 contain multiples of three nucleotides. The impact of in-frame exon skipping is yet to be determined. Antisense oligonucleotides (AONs) have been investigated in Usher syndrome-associated genes to induce skipping of in-frame exons carrying severe variants and mitigate their disease-linked effect. Upon the identification of a STGD1 proband carrying a novel exon 17 canonical splice site variant, the activity of ABCA4 lacking 22 amino acids encoded by exon 17 was examined, followed by design of AONs able to induce exon 17 skipping. METHODS A STGD1 proband was compound heterozygous for the splice variant c.2653+1G>A, that was predicted to result in in-frame skipping of exon 17, and a null variant [c.735T>G, p.(Tyr245*)]. Clinical characteristics of this proband were studied using multi-modal imaging and complete ophthalmological examination. The aberrant splicing of c.2653+1G>A was investigated in vitro in HEK293T cells with wild-type and mutant midigenes. The residual activity of the mutant ABCA4 protein lacking Asp864-Gly885 encoded by exon 17 was analyzed with all-trans-retinal-activated ATPase activity assay, along with its subcellular localization. To induce exon 17 skipping, the effect of 40 AONs was examined in vitro in WT WERI-Rb-1 cells and 3D human retinal organoids. RESULTS Late onset STGD1 in the proband suggests that c.2653+1G>A does not have a fully deleterious effect. The in vitro splice assay confirmed that this variant leads to ABCA4 transcripts without exon 17. ABCA4 Asp864_Gly863del was stable and retained 58% all-trans-retinal-activated ATPase activity compared to WT ABCA4. This sequence is located in an unstructured linker region between transmembrane domain 6 and nucleotide-binding domain-1 of ABCA4. AONs were designed to possibly reduce pathogenicity of severe variants harbored in exon 17. The best AON achieved 59% of exon 17 skipping in retinal organoids. CONCLUSIONS Exon 17 deletion in ABCA4 does not result in the absence of protein activity and does not cause a severe STGD1 phenotype when in trans with a null allele. By applying AONs, the effect of severe variants in exon 17 can potentially be ameliorated by exon skipping, thus generating partial ABCA4 activity in STGD1 patients.
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Affiliation(s)
- Melita Kaltak
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
- ProQR Therapeutics, Leiden, The Netherlands
| | - Rocio Blanco-Garavito
- Department of Ophthalmology, Intercommunal Hospital Center and Henri Mondor Hospital, Paris-Est Créteil University, Creteil, France
| | - Laurie L Molday
- Department of Biochemistry and Molecular Biology, Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, BC, Canada
| | - Claire-Marie Dhaenens
- University of Lille, Inserm, CHU Lille, U1172-LilNCog-Lille Neuroscience & Cognition, Lille, France
| | - Eric E Souied
- Department of Ophthalmology, Intercommunal Hospital Center and Henri Mondor Hospital, Paris-Est Créteil University, Creteil, France
| | | | | | - Robert S Molday
- Department of Biochemistry and Molecular Biology, Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, BC, Canada
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.
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Al-Khuzaei S, Broadgate S, Foster CR, Shah M, Yu J, Downes SM, Halford S. An Overview of the Genetics of ABCA4 Retinopathies, an Evolving Story. Genes (Basel) 2021; 12:1241. [PMID: 34440414 PMCID: PMC8392661 DOI: 10.3390/genes12081241] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 11/16/2022] Open
Abstract
Stargardt disease (STGD1) and ABCA4 retinopathies (ABCA4R) are caused by pathogenic variants in the ABCA4 gene inherited in an autosomal recessive manner. The gene encodes an importer flippase protein that prevents the build-up of vitamin A derivatives that are toxic to the RPE. Diagnosing ABCA4R is complex due to its phenotypic variability and the presence of other inherited retinal dystrophy phenocopies. ABCA4 is a large gene, comprising 50 exons; to date > 2000 variants have been described. These include missense, nonsense, splicing, structural, and deep intronic variants. Missense variants account for the majority of variants in ABCA4. However, in a significant proportion of patients with an ABCA4R phenotype, a second variant in ABCA4 is not identified. This could be due to the presence of yet unknown variants, or hypomorphic alleles being incorrectly classified as benign, or the possibility that the disease is caused by a variant in another gene. This underlines the importance of accurate genetic testing. The pathogenicity of novel variants can be predicted using in silico programs, but these rely on databases that are not ethnically diverse, thus highlighting the need for studies in differing populations. Functional studies in vitro are useful towards assessing protein function but do not directly measure the flippase activity. Obtaining an accurate molecular diagnosis is becoming increasingly more important as targeted therapeutic options become available; these include pharmacological, gene-based, and cell replacement-based therapies. The aim of this review is to provide an update on the current status of genotyping in ABCA4 and the status of the therapeutic approaches being investigated.
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Affiliation(s)
- Saoud Al-Khuzaei
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK; (S.A.-K.); (M.S.)
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | - Suzanne Broadgate
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | | | - Mital Shah
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK; (S.A.-K.); (M.S.)
| | - Jing Yu
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | - Susan M. Downes
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK; (S.A.-K.); (M.S.)
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | - Stephanie Halford
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
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Camp DA, Gemayel MC, Ciulla TA. Understanding the genetic pathology of Stargardt disease: a review of current findings and challenges. Expert Opin Orphan Drugs 2021. [DOI: 10.1080/21678707.2021.1898373] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- David A. Camp
- Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michael C. Gemayel
- Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Thomas A. Ciulla
- Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, USA
- Retina Service, Midwest Eye Institute, Indianapolis, IN, USA
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5
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Del Pozo-Valero M, Riveiro-Alvarez R, Blanco-Kelly F, Aguirre-Lamban J, Martin-Merida I, Iancu IF, Swafiri S, Lorda-Sanchez I, Rodriguez-Pinilla E, Trujillo-Tiebas MJ, Jimenez-Rolando B, Carreño E, Mahillo-Fernandez I, Rivolta C, Corton M, Avila-Fernandez A, Garcia-Sandoval B, Ayuso C. Genotype-Phenotype Correlations in a Spanish Cohort of 506 Families With Biallelic ABCA4 Pathogenic Variants. Am J Ophthalmol 2020; 219:195-204. [PMID: 32619608 DOI: 10.1016/j.ajo.2020.06.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 06/19/2020] [Accepted: 06/21/2020] [Indexed: 01/28/2023]
Abstract
PURPOSE To define genotype-phenotype correlations in the largest cohort study worldwide of patients with biallelic ABCA4 variants, including 434 patients with Stargardt disease (STGD1) and 72 with cone-rod dystrophy (CRD). DESIGN Cohort study. METHODS We characterized 506 patients with ABCA4 variants using conventional genetic tools and next-generation sequencing technologies. Medical history and ophthalmologic data were obtained from 372 patients. Genotype-phenotype correlation studies were carried out for the following variables: variant type, age at symptom onset (AO), and clinical phenotype. RESULTS A total of 228 different pathogenic variants were identified in 506 ABCA4 patients, 50 of which were novel. Genotype-phenotype correlations showed that most of the patients with biallelic truncating variants presented with CRD and that these cases had a significantly earlier AO than patients with STGD1. Three missense variants are associated with CRD for the first time (c.1804C>T; p.[Arg602Trp], c.3056C>T; p.[Thr1019Met], and c.6320G>C; p.[Arg2107Pro]). Analysis of the most prevalent ABCA4 variant in Spain, c.3386G>T; p.(Arg1129Leu), revealed that is correlated to STGD1, later AO, and foveal sparing. CONCLUSIONS Our study, conducted in the largest ABCA4-associated disease cohort reported to date, updates the genotype-phenotype model established for ABCA4 variants and broadens the mutational spectrum of the gene. According to our observations, patients with ABCA4 presenting with 2 truncating variants may first present features of STGD1 but eventually develop rod dysfunction, and specific missense variants may be associated with a different phenotype, underscoring the importance of an accurate genetic diagnosis. Also, it is a prerequisite for enrollment in clinical trials, and to date, no other treatment has been approved for STGD1.
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Affiliation(s)
- Marta Del Pozo-Valero
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Rosa Riveiro-Alvarez
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Fiona Blanco-Kelly
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Jana Aguirre-Lamban
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Inmaculada Martin-Merida
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Ionut-Florin Iancu
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Saoud Swafiri
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Isabel Lorda-Sanchez
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Elvira Rodriguez-Pinilla
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Maria José Trujillo-Tiebas
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Belen Jimenez-Rolando
- Department of Ophthalmology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Ester Carreño
- Department of Ophthalmology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Ignacio Mahillo-Fernandez
- Department of Epidemiology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Carlo Rivolta
- Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland; Department of Ophthalmology, University Hospital Basel, Switzerland; Department of Genetics and Genome Biology, University of Leicester, Leicester, United Kingdom
| | - Marta Corton
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Almudena Avila-Fernandez
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain
| | - Blanca Garcia-Sandoval
- Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain; Department of Ophthalmology, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain
| | - Carmen Ayuso
- Department of Genetics, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid, Madrid, Spain; Center for Biomedical Network Research on Rare Diseases, Instituto de Salud Carlos III, Madrid, Spain.
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6
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Cremers FPM, Lee W, Collin RWJ, Allikmets R. Clinical spectrum, genetic complexity and therapeutic approaches for retinal disease caused by ABCA4 mutations. Prog Retin Eye Res 2020; 79:100861. [PMID: 32278709 PMCID: PMC7544654 DOI: 10.1016/j.preteyeres.2020.100861] [Citation(s) in RCA: 166] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 03/13/2020] [Accepted: 03/18/2020] [Indexed: 12/18/2022]
Abstract
The ABCA4 protein (then called a “rim protein”) was first
identified in 1978 in the rims and incisures of rod photoreceptors. The
corresponding gene, ABCA4, was cloned in 1997, and variants
were identified as the cause of autosomal recessive Stargardt disease (STGD1).
Over the next two decades, variation in ABCA4 has been
attributed to phenotypes other than the classically defined STGD1 or fundus
flavimaculatus, ranging from early onset and fast progressing cone-rod dystrophy
and retinitis pigmentosa-like phenotypes to very late onset cases of mostly mild
disease sometimes resembling, and confused with, age-related macular
degeneration. Similarly, analysis of the ABCA4 locus uncovered
a trove of genetic information, including >1200 disease-causing mutations
of varying severity, and of all types – missense, nonsense, small
deletions/insertions, and splicing affecting variants, of which many are located
deep-intronic. Altogether, this has greatly expanded our understanding of
complexity not only of the diseases caused by ABCA4 mutations,
but of all Mendelian diseases in general. This review provides an in depth
assessment of the cumulative knowledge of ABCA4-associated retinopathy –
clinical manifestations, genetic complexity, pathophysiology as well as current
and proposed therapeutic approaches.
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Affiliation(s)
- Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, the Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9104, 6500 HE, Nijmegen, the Netherlands.
| | - Winston Lee
- Department of Ophthalmology, Columbia University, New York, NY, 10032, USA; Department of Genetics & Development, Columbia University, New York, NY, 10032, USA
| | - Rob W J Collin
- Department of Human Genetics, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, the Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, PO Box 9104, 6500 HE, Nijmegen, the Netherlands
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, NY, 10032, USA; Department of Pathology & Cell Biology, Columbia University, New York, NY, 10032, USA.
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7
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Tracewska AM, Kocyła-Karczmarewicz B, Rafalska A, Murawska J, Jakubaszko-Jablonska J, Rydzanicz M, Stawiński P, Ciara E, Khan MI, Henkes A, Hoischen A, Gilissen C, van de Vorst M, Cremers FPM, Płoski R, Chrzanowska KH. Genetic Spectrum of ABCA4-Associated Retinal Degeneration in Poland. Genes (Basel) 2019; 10:E959. [PMID: 31766579 PMCID: PMC6947411 DOI: 10.3390/genes10120959] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/05/2019] [Accepted: 11/19/2019] [Indexed: 12/03/2022] Open
Abstract
Mutations in retina-specific ATP-binding cassette transporter 4 (ABCA4) are responsible for over 95% of cases of Stargardt disease (STGD), as well as a minor proportion of retinitis pigmentosa (RP) and cone-rod dystrophy cases (CRD). Since the knowledge of the genetic causes of inherited retinal diseases (IRDs) in Poland is still scarce, the purpose of this study was to identify pathogenic ABCA4 variants in a subgroup of Polish IRD patients. We recruited 67 families with IRDs as a part of a larger study. The patients were screened with next generation sequencing using a molecular inversion probes (MIPs)-based technique targeting 108 genes involved in the pathogenesis of IRDs. All identified mutations were validated and their familial segregation was tested using Sanger sequencing. In the case of the most frequent complex allele, consisting of two variants in exon 12 and 21, familial segregation was tested using restriction fragment length polymorphism (RFLP). The most prevalent variant, a complex change c.[1622T>C;3113C>T], p.[Leu541Pro;Ala1038Val], was found in this cohort in 54% of all solved ABCA4-associated disorder cases, which is the highest frequency reported thus far. Additionally, we identified nine families displaying a pseudo-dominant mode of inheritance, indicating a high frequency of pathogenic variants within this population.
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Affiliation(s)
- Anna M. Tracewska
- DNA Analysis Unit, ŁUKASIEWICZ Research Network–PORT Polish Center for Technology Development, 54-066 Wrocław, Poland
| | | | - Agnieszka Rafalska
- Department of Ophthalmology, Wrocław Medical University, 50-556 Wrocław, Poland; (A.R.); (J.J.-J.)
| | - Joanna Murawska
- Department of Ophthalmology, University Clinical Centre, 80-214 Gdańsk, Poland;
| | - Joanna Jakubaszko-Jablonska
- Department of Ophthalmology, Wrocław Medical University, 50-556 Wrocław, Poland; (A.R.); (J.J.-J.)
- Department of Paediatric Traumatology and Emergency Medicine, Wrocław Medical University, 50-345 Wrocław, Poland
- SPEKTRUM Ophthalmology Clinic, 53-334 Wrocław, Poland
| | - Małgorzata Rydzanicz
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland; (M.R.); (P.S.); (R.P.)
| | - Piotr Stawiński
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland; (M.R.); (P.S.); (R.P.)
| | - Elżbieta Ciara
- Children’s Memorial Health Institute, 04-730 Warsaw, Poland; (B.K.-K.); (E.C.)
| | - Muhammad Imran Khan
- Department of Human Genetics, Radboud university medical center, PO Box 9101, 6500 HB Nijmegen, The Netherland; (M.I.K.); (A.H.); (A.H.); (M.v.d.V.); (F.P.M.C.)
- Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, PO Box 9104, 6500 HE Nijmegen, The Netherlands;
| | - Arjen Henkes
- Department of Human Genetics, Radboud university medical center, PO Box 9101, 6500 HB Nijmegen, The Netherland; (M.I.K.); (A.H.); (A.H.); (M.v.d.V.); (F.P.M.C.)
- Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, PO Box 9104, 6500 HE Nijmegen, The Netherlands;
| | - Alexander Hoischen
- Department of Human Genetics, Radboud university medical center, PO Box 9101, 6500 HB Nijmegen, The Netherland; (M.I.K.); (A.H.); (A.H.); (M.v.d.V.); (F.P.M.C.)
- Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Christian Gilissen
- Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, PO Box 9104, 6500 HE Nijmegen, The Netherlands;
- Department of Internal Medicine and Radboud Center for Infectious Diseases (RCI), Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Maartje van de Vorst
- Department of Human Genetics, Radboud university medical center, PO Box 9101, 6500 HB Nijmegen, The Netherland; (M.I.K.); (A.H.); (A.H.); (M.v.d.V.); (F.P.M.C.)
- Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, PO Box 9104, 6500 HE Nijmegen, The Netherlands;
| | - Frans P. M. Cremers
- Department of Human Genetics, Radboud university medical center, PO Box 9101, 6500 HB Nijmegen, The Netherland; (M.I.K.); (A.H.); (A.H.); (M.v.d.V.); (F.P.M.C.)
- Donders Institute for Brain, Cognition and Behavior, Radboud University Medical Center, PO Box 9104, 6500 HE Nijmegen, The Netherlands;
| | - Rafał Płoski
- Department of Medical Genetics, Medical University of Warsaw, 02-106 Warsaw, Poland; (M.R.); (P.S.); (R.P.)
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8
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Runhart EH, Sangermano R, Cornelis SS, Verheij JBGM, Plomp AS, Boon CJF, Lugtenberg D, Roosing S, Bax NM, Blokland EAW, Jacobs-Camps MHM, van der Velde-Visser SD, Pott JWR, Rohrschneider K, Thiadens AAHJ, Klaver CCW, van den Born LI, Hoyng CB, Cremers FPM. The Common ABCA4 Variant p.Asn1868Ile Shows Nonpenetrance and Variable Expression of Stargardt Disease When Present in trans With Severe Variants. Invest Ophthalmol Vis Sci 2019; 59:3220-3231. [PMID: 29971439 DOI: 10.1167/iovs.18-23881] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To assess the occurrence and the disease expression of the common p.Asn1868Ile variant in patients with Stargardt disease (STGD1) harboring known, monoallelic causal ABCA4 variants. Methods The coding and noncoding regions of ABCA4 were sequenced in 67 and 63 STGD1 probands respectively, harboring monoallelic ABCA4 variants. In case p.Asn1868Ile was detected, segregation analysis was performed whenever possible. Probands and affected siblings harboring p.Asn1868Ile without additional variants in cis were clinically evaluated retrospectively. Two asymptomatic siblings carrying the same ABCA4 variants as their probands were clinically examined. The penetrance of p.Asn1868Ile was calculated using allele frequency data of ABCA4 variants in non-Finnish European individuals. Results The p.Asn1868Ile variant was found in cis with known variants in 14/67 probands. In 27/67 probands, we identified p.Asn1868Ile without additional variants in cis, in combination with known, mainly severe ABCA4 variants. In 23/27 probands, the trans configuration was established. Among 27 probands and 6/7 STGD1 siblings carrying p.Asn1868Ile, 42% manifested late-onset disease (>44 years). We additionally identified four asymptomatic relatives carrying a combination of a severe variant and p.Asn1868Ile; ophthalmologic examination in two persons did not reveal STGD1. Based on ABCA4 allele frequency data, we conservatively estimated the penetrance of p.Asn1868Ile, when present in trans with a severe variant, to be below 5%. Conclusions A significant fraction of genetically unexplained STGD1 cases carries p.Asn1868Ile as a second variant. Our findings suggest exceptional differences in disease expression or even nonpenetrance of this ABCA4 variant, pointing toward an important role for genetic or environmental modifiers in STGD1.
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Affiliation(s)
- Esmee H Runhart
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Riccardo Sangermano
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Radboud Institute of Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Stéphanie S Cornelis
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Joke B G M Verheij
- Department of Medical Genetics, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Astrid S Plomp
- Department of Clinical Genetics, Academic Medical Center, Amsterdam, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands.,Department of Ophthalmology, Academic Medical Center, Amsterdam, The Netherlands
| | - Dorien Lugtenberg
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Susanne Roosing
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Nathalie M Bax
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Ellen A W Blokland
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | | | - Jan-Willem R Pott
- Department of Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Klaus Rohrschneider
- Universitätsaugenklinik, Ruprecht-Karls-Universität, Heidelberg, Heidelberg, Germany
| | - Alberta A H J Thiadens
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Caroline C W Klaver
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands.,Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | | | - Carel B Hoyng
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
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9
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Bauwens M, Garanto A, Sangermano R, Naessens S, Weisschuh N, De Zaeytijd J, Khan M, Sadler F, Balikova I, Van Cauwenbergh C, Rosseel T, Bauwens J, De Leeneer K, De Jaegere S, Van Laethem T, De Vries M, Carss K, Arno G, Fakin A, Webster AR, de Ravel de l'Argentière TJL, Sznajer Y, Vuylsteke M, Kohl S, Wissinger B, Cherry T, Collin RWJ, Cremers FPM, Leroy BP, De Baere E. ABCA4-associated disease as a model for missing heritability in autosomal recessive disorders: novel noncoding splice, cis-regulatory, structural, and recurrent hypomorphic variants. Genet Med 2019; 21:1761-1771. [PMID: 30670881 PMCID: PMC6752479 DOI: 10.1038/s41436-018-0420-y] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 12/17/2018] [Indexed: 12/30/2022] Open
Abstract
Purpose ABCA4-associated disease, a recessive retinal dystrophy, is hallmarked by a large proportion of patients with only one pathogenic ABCA4 variant, suggestive for missing heritability. Methods By locus-specific analysis of ABCA4, combined with extensive functional studies, we aimed to unravel the missing alleles in a cohort of 67 patients (p), with one (p = 64) or no (p = 3) identified coding pathogenic variants of ABCA4. Results We identified eight pathogenic (deep-)intronic ABCA4 splice variants, of which five are novel and six structural variants, four of which are novel, including two duplications. Together, these variants account for the missing alleles in 40.3% of patients. Furthermore, two novel variants with a putative cis-regulatory effect were identified. The common hypomorphic variant c.5603A>T p.(Asn1868Ile) was found as a candidate second allele in 43.3% of patients. Overall, we have elucidated the missing heritability in 83.6% of our cohort. In addition, we successfully rescued three deep-intronic variants using antisense oligonucleotide (AON)-mediated treatment in HEK 293-T cells and in patient-derived fibroblast cells. Conclusion Noncoding pathogenic variants, novel structural variants, and a common hypomorphic allele of the ABCA4 gene explain the majority of unsolved cases with ABCA4-associated disease, rendering this retinopathy a model for missing heritability in autosomal recessive disorders.
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Affiliation(s)
- Miriam Bauwens
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Alejandro Garanto
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Riccardo Sangermano
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Sarah Naessens
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Nicole Weisschuh
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Julie De Zaeytijd
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Mubeen Khan
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Françoise Sadler
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Irina Balikova
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Caroline Van Cauwenbergh
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium.,Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Toon Rosseel
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Jim Bauwens
- Department of Computer Science, Free University of Brussels, Brussels, Belgium
| | - Kim De Leeneer
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Sarah De Jaegere
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Thalia Van Laethem
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Meindert De Vries
- Department of Ophthalmology, Hôpital des Enfants Reine Fabiola, Brussels, Belgium
| | - Keren Carss
- Department of Haematology, University of Cambridge, NHS Blood and Transplant Centre, Cambridge, UK.,UK NIHR BioResource, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge, UK
| | - Gavin Arno
- UCL Institute of Ophthalmology, London, UK
| | - Ana Fakin
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Andrew R Webster
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | | | - Yves Sznajer
- Centre de Génétique Humaine, Cliniques Universitaires St. Luc, Université Catholique de Louvain, Brussels, Belgium
| | | | - Susanne Kohl
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Bernd Wissinger
- Molecular Genetics Laboratory, Institute for Ophthalmic Research, University of Tuebingen, Tuebingen, Germany
| | - Timothy Cherry
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, USA.,Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA, USA
| | - Rob W J Collin
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bart P Leroy
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium.,Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium.,Division of Ophthalmology and Center for Cellular & Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Elfride De Baere
- Center for Medical Genetics Ghent, Ghent University and Ghent University Hospital, Ghent, Belgium.
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10
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Cheung SW, Bi W. Novel applications of array comparative genomic hybridization in molecular diagnostics. Expert Rev Mol Diagn 2018; 18:531-542. [PMID: 29848116 DOI: 10.1080/14737159.2018.1479253] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
INTRODUCTION In 2004, the implementation of array comparative genomic hybridization (array comparative genome hybridization [CGH]) into clinical practice marked a new milestone for genetic diagnosis. Array CGH and single-nucleotide polymorphism (SNP) arrays enable genome-wide detection of copy number changes in a high resolution, and therefore microarray has been recognized as the first-tier test for patients with intellectual disability or multiple congenital anomalies, and has also been applied prenatally for detection of clinically relevant copy number variations in the fetus. Area covered: In this review, the authors summarize the evolution of array CGH technology from their diagnostic laboratory, highlighting exonic SNP arrays developed in the past decade which detect small intragenic copy number changes as well as large DNA segments for the region of heterozygosity. The applications of array CGH to human diseases with different modes of inheritance with the emphasis on autosomal recessive disorders are discussed. Expert commentary: An exonic array is a powerful and most efficient clinical tool in detecting genome wide small copy number variants in both dominant and recessive disorders. However, whole-genome sequencing may become the single integrated platform for detection of copy number changes, single-nucleotide changes as well as balanced chromosomal rearrangements in the near future.
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Affiliation(s)
- Sau W Cheung
- a Department of Molecular and Human Genetics , Baylor College of Medicine , Houston , TX , USA
| | - Weimin Bi
- a Department of Molecular and Human Genetics , Baylor College of Medicine , Houston , TX , USA.,b Baylor Genetics , Houston , TX , USA
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11
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Phenotypic Progression of Stargardt Disease in a Large Consanguineous Tunisian Family Harboring New ABCA4 Mutations. J Ophthalmol 2018; 2018:1030184. [PMID: 29736279 PMCID: PMC5875050 DOI: 10.1155/2018/1030184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Revised: 12/29/2017] [Accepted: 02/01/2018] [Indexed: 12/01/2022] Open
Abstract
To assess the progression of Stargardt (STGD) disease over nine years in two branches of a large consanguineous Tunisian family. Initially, different phenotypes were observed with clinical intra- and interfamilial variations. At presentation, four different retinal phenotypes were observed. In phenotype 1, bull's eye maculopathy and slight alteration of photopic responses in full-field electroretinography were observed in the youngest child. In phenotype 2, macular atrophy and yellow white were observed in two brothers. In phenotype 3, diffuse macular, peripapillary, and peripheral RPE atrophy and hyperfluorescent dots were observed in two sisters. In phenotype 4, Stargardt disease-fundus flavimaculatus phenotype was observed in two cousins with later age of onset. After a progression of 9 years, all seven patients displayed the same phenotype 3 with advanced stage STGD and diffuse atrophy. WES and MLPA identified two ABCA4 mutations M1: c.[(?_4635)_(5714+?)dup; (?_6148)_(6479_+?) del] and M2: c.[2041C>T], p.[R681∗]. In one branch, the three affected patients had M1/M1 causal mutations and in the other branch the two affected patients had M1/M2 causal mutations. After 9-year follow-up, all patients showed the same phenotypic evolution, confirming the progressive nature of the disease. Genetic variations in the two branches made no difference to similar end-stage disease.
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12
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Abeshi A, Zulian A, Beccari T, Dundar M, Ziccardi L, Bertelli M. Genetic testing for cone rod dystrophies. EUROBIOTECH JOURNAL 2017. [DOI: 10.24190/issn2564-615x/2017/s1.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Abstract
We studied the scientific literature and disease guidelines in order to summarize the clinical utility of the genetic test for cone rod dystrophies (CORDs). CORDs are caused by variations in the ABCA4, ADAM9, AIPL1, C8orf37, CACNA1F, CACNA2D4, CDHR1, CNGA3, CRX, DRAM2, GUCA1A, GUCY2D, HRG4, KCNV2, PDE6C, PITPNM3, POC1B, PROM1, PRPH2, RAB28, RAX2, RIMS1, RPGRIP1, RPGR SEMA4A, TTLL5 genes, with an overall prevalence of 1 per 40 000. Most genes have autosomal recessive inheritance; the others have autosomal dominant or X-linked recessive transmission. Clinical diagnosis is based on clinical findings, color vision testing, ophthalmological examination and electroretinography. The genetic test is useful for confirming diagnosis, and for differential diagnosis, couple risk assessment and access to clinical trials.
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Affiliation(s)
- Andi Abeshi
- MAGI Balkans, Tirana , Albania
- MAGI’S Lab, Rovereto , Italy
| | | | - Tommaso Beccari
- Department of Pharmaceutical Sciences, University of Perugia, Perugia , Italy
| | - Munis Dundar
- Department of Medical Genetics, Erciyes University Medical School, Kayseri , Turkey
| | - Lucia Ziccardi
- Neurophthalmology Unit, “G.B. Bietti” Foundation IRCCS, Rome , Italy
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13
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Schulz HL, Grassmann F, Kellner U, Spital G, Rüther K, Jägle H, Hufendiek K, Rating P, Huchzermeyer C, Baier MJ, Weber BHF, Stöhr H. Mutation Spectrum of the ABCA4 Gene in 335 Stargardt Disease Patients From a Multicenter German Cohort-Impact of Selected Deep Intronic Variants and Common SNPs. Invest Ophthalmol Vis Sci 2017; 58:394-403. [PMID: 28118664 PMCID: PMC5270621 DOI: 10.1167/iovs.16-19936] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Purpose Stargardt disease (STGD1) is an autosomal recessive retinopathy, caused by mutations in the retina-specific ATP-binding cassette transporter (ABCA4) gene. To establish the mutational spectrum and to assess effects of selected deep intronic and common genetic variants on disease, we performed a comprehensive sequence analysis in a large cohort of German STGD1 patients. Methods DNA samples of 335 STGD1 patients were analyzed for ABCA4 mutations in its 50 coding exons and adjacent intronic sequences by resequencing array technology or next generation sequencing (NGS). Parts of intron 30 and 36 were screened by Sanger chain-terminating dideoxynucleotide sequencing. An in vitro splicing assay was used to test selected variants for their splicing behavior. By logistic regression analysis we assessed the association of common ABCA4 alleles while a multivariate logistic regression model calculated a genetic risk score (GRS). Results Our analysis identified 148 pathogenic or likely pathogenic mutations, of which 48 constitute so far unpublished ABCA4-associated disease alleles. Four rare deep intronic variants were found once in 472 alleles analyzed. In addition, we identified six risk-modulating common variants. Genetic risk score estimates suggest that defined common ABCA4 variants influence disease risk in carriers of a single pathogenic ABCA4 allele. Conclusions Our study adds to the mutational spectrum of the ABCA4 gene. Moreover, in our cohort, deep intronic variants in intron 30 and 36 likely play no or only a minor role in disease pathology. Of note, our findings demonstrate a possible modifying effect of common sequence variants on ABCA4-associated disease.
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Affiliation(s)
- Heidi L Schulz
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Felix Grassmann
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Ulrich Kellner
- Rare Retinal Disease Center, AugenZentrum Siegburg, MVZ ADTC Siegburg GmbH, Siegburg, Germany 3RetinaScience, Bonn, Germany
| | - Georg Spital
- Department of Ophthalmology, St. Franziskus-Hospital, Münster, Germany
| | | | - Herbert Jägle
- Department of Ophthalmology, University Hospital Regensburg, Regensburg, Germany
| | | | - Philipp Rating
- Department of Ophthalmology, University Hospital Essen, Essen, Germany
| | - Cord Huchzermeyer
- Department of Ophthalmology, University Hospital Erlangen, Erlangen, Germany
| | - Maria J Baier
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Heidi Stöhr
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
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14
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Cornelis SS, Bax NM, Zernant J, Allikmets R, Fritsche LG, den Dunnen JT, Ajmal M, Hoyng CB, Cremers FPM. In Silico Functional Meta-Analysis of 5,962 ABCA4 Variants in 3,928 Retinal Dystrophy Cases. Hum Mutat 2017; 38:400-408. [PMID: 28044389 DOI: 10.1002/humu.23165] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 12/20/2016] [Accepted: 12/27/2016] [Indexed: 12/26/2022]
Abstract
Variants in the ABCA4 gene are associated with a spectrum of inherited retinal diseases (IRDs), most prominently with autosomal recessive (ar) Stargardt disease (STGD1) and ar cone-rod dystrophy. The clinical outcome to a large degree depends on the severity of the variants. To provide an accurate prognosis and to select patients for novel treatments, functional significance assessment of nontruncating ABCA4 variants is important. We collected all published ABCA4 variants from 3,928 retinal dystrophy cases in a Leiden Open Variation Database, and compared their frequency in 3,270 Caucasian IRD cases with 33,370 non-Finnish European control individuals. Next to the presence of 270 protein-truncating variants, 191 nontruncating variants were significantly enriched in the patient cohort. Furthermore, 30 variants were deemed benign. Assessing the homozygous occurrence of frequent variants in IRD cases based on the allele frequencies in control individuals confirmed the mild nature of the p.[Gly863Ala, Gly863del] variant and identified three additional mild variants (p.(Ala1038Val), c.5714+5G>A, and p.(Arg2030Gln)). The p.(Gly1961Glu) variant was predicted to act as a mild variant in most cases. Based on these data, in silico analyses, and American College of Medical Genetics and Genomics guidelines, we provide pathogenicity classifications on a five-tier scale from benign to pathogenic for all variants in the ABCA4-LOVD database.
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Affiliation(s)
- Stéphanie S Cornelis
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Nathalie M Bax
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
| | - Jana Zernant
- Department of Ophthalmology, Columbia University, New York, New York
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, New York.,Department of Pathology & Cell Biology, Columbia University, New York, New York
| | - Lars G Fritsche
- Department of Public Health, K.G. Jebsen Center for Genetic Epidemiology, NTNU, Norwegian University of Science and Technology, Trondheim, Norway
| | - Johan T den Dunnen
- Departments of Clinical Genetics and Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Muhammad Ajmal
- Department of Biosciences, Faculty of Science, COMSATS Institute of Information Technology, Islamabad, Pakistan
| | - Carel B Hoyng
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
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15
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Mitra RN, Zheng M, Han Z. Nanoparticle-motivated gene delivery for ophthalmic application. WILEY INTERDISCIPLINARY REVIEWS. NANOMEDICINE AND NANOBIOTECHNOLOGY 2016; 8:160-74. [PMID: 26109528 PMCID: PMC4688250 DOI: 10.1002/wnan.1356] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 05/21/2015] [Accepted: 05/23/2015] [Indexed: 12/24/2022]
Abstract
Ophthalmic gene therapy is an intellectual and intentional manipulation of desired gene expression into the specific cells of an eye for the treatment of ophthalmic (ocular) genetic dystrophies and pathological conditions. Exogenous nucleic acids such as DNA, small interfering RNA, micro RNA, and so on, are used for the purpose of managing expression of the desired therapeutic proteins in ocular tissues. The delivery of unprotected nucleic acids into the cells is limited because of exogenous and endogenous degradation modalities. Nanotechnology, a promising and sophisticated cutting edge tool, works as a protective shelter for these therapeutic nucleic acids. They can be safely delivered to the required cells in order to modulate anticipated protein expression. To this end, nanotechnology is seen as a potential and promising strategy in the field of ocular gene delivery. This review focused on current nanotechnology modalities and other promising nonviral strategies being used to deliver therapeutic genes in order to treat various devastating ocular diseases.
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Affiliation(s)
| | - Min Zheng
- Department of Ophthalmology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Zongchao Han
- Department of Ophthalmology, University of North Carolina, Chapel Hill, NC 27599, USA
- Carolina Institute for NanoMedicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Division of Molecular Pharmaceutics, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA
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16
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Complex inheritance of ABCA4 disease: four mutations in a family with multiple macular phenotypes. Hum Genet 2015; 135:9-19. [PMID: 26527198 DOI: 10.1007/s00439-015-1605-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 10/01/2015] [Indexed: 01/12/2023]
Abstract
Over 800 mutations in the ABCA4 gene cause autosomal recessive Stargardt disease. Due to extensive genetic heterogeneity, observed variant-associated phenotypes can manifest tremendous variability of expression. Furthermore, the high carrier frequency of pathogenic ABCA4 alleles in the general population (~1:20) often results in pseudo-dominant inheritance patterns further complicating the diagnosis and characterization of affected individuals. This study describes a genotype/phenotype analysis of an unusual family with multiple macular disease phenotypes spanning across two generations and segregating four distinct ABCA4 mutant alleles. Complete sequencing of ABCA4 discovered two known missense mutations, p.C54Y and p.G1961E. Array comparative genomic hybridization revealed a large novel deletion combined with a small insertion, c.6148-698_c.6670del/insTGTGCACCTCCCTAG, and complete sequencing of the entire ABCA4 genomic locus uncovered a new deep intronic variant, c.302+68C>T. Patients with the p.G1961E mutation had the mildest, confined maculopathy phenotype with peripheral flecks while those with all other mutant allele combinations exhibited a more advanced stage of generalized retinal and choriocapillaris atrophy. This family epitomizes the clinical and genetic complexity of ABCA4-associated diseases. It contained variants from all classes of mutations, in the coding region, deep intronic, both single nucleotide variants and copy number variants that accounted for varying phenotypes segregating in an apparent dominant fashion. Unequivocally defining disease-associated alleles in the ABCA4 locus requires a multifaceted approach that includes advanced mutation detection methods and a thorough analysis of clinical phenotypes.
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17
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Bax NM, Sangermano R, Roosing S, Thiadens AAHJ, Hoefsloot LH, van den Born LI, Phan M, Klevering BJ, Westeneng-van Haaften C, Braun TA, Zonneveld-Vrieling MN, de Wijs I, Mutlu M, Stone EM, den Hollander AI, Klaver CCW, Hoyng CB, Cremers FPM. Heterozygous deep-intronic variants and deletions in ABCA4 in persons with retinal dystrophies and one exonic ABCA4 variant. Hum Mutat 2015; 36:43-7. [PMID: 25363634 DOI: 10.1002/humu.22717] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/18/2014] [Indexed: 11/05/2022]
Abstract
Variants in ABCA4 are responsible for autosomal-recessive Stargardt disease and cone-rod dystrophy. Sequence analysis of ABCA4 exons previously revealed one causative variant in each of 45 probands. To identify the "missing" variants in these cases, we performed multiplex ligation-dependent probe amplification-based deletion scanning of ABCA4. In addition, we sequenced the promoter region, fragments containing five deep-intronic splice variants, and 15 deep-intronic regions containing weak splice sites. Heterozygous deletions spanning ABCA4 exon 5 or exons 20-22 were found in two probands, heterozygous deep-intronic variants were identified in six probands, and a deep-intronic variant was found together with an exon 20-22 deletion in one proband. Based on ophthalmologic findings and characteristics of the identified exonic variants present in trans, the deep-intronic variants V1 and V4 were predicted to be relatively mild and severe, respectively. These findings are important for proper genetic counseling and for the development of variant-specific therapies.
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Affiliation(s)
- Nathalie M Bax
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
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18
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Boulanger-Scemama E, El Shamieh S, Démontant V, Condroyer C, Antonio A, Michiels C, Boyard F, Saraiva JP, Letexier M, Souied E, Mohand-Saïd S, Sahel JA, Zeitz C, Audo I. Next-generation sequencing applied to a large French cone and cone-rod dystrophy cohort: mutation spectrum and new genotype-phenotype correlation. Orphanet J Rare Dis 2015; 10:85. [PMID: 26103963 PMCID: PMC4566196 DOI: 10.1186/s13023-015-0300-3] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 06/15/2015] [Indexed: 12/21/2022] Open
Abstract
Background Cone and cone-rod dystrophies are clinically and genetically heterogeneous inherited retinal disorders with predominant cone impairment. They should be distinguished from the more common group of rod-cone dystrophies (retinitis pigmentosa) due to their more severe visual prognosis with early central vision loss. The purpose of our study was to document mutation spectrum of a large French cohort of cone and cone-rod dystrophies. Methods We applied Next-Generation Sequencing targeting a panel of 123 genes implicated in retinal diseases to 96 patients. A systematic filtering approach was used to identify likely disease causing variants, subsequently confirmed by Sanger sequencing and co-segregation analysis when possible. Results Overall, the likely causative mutations were detected in 62.1 % of cases, revealing 33 known and 35 novel mutations. This rate was higher for autosomal dominant (100 %) than autosomal recessive cases (53.8 %). Mutations in ABCA4 and GUCY2D were responsible for 19.2 % and 29.4 % of resolved cases with recessive and dominant inheritance, respectively. Furthermore, unexpected genotype-phenotype correlations were identified, confirming the complexity of inherited retinal disorders with phenotypic overlap between cone-rod dystrophies and other retinal diseases. Conclusions In summary, this time-efficient approach allowed mutation detection in the most important cohort of cone-rod dystrophies investigated so far covering the largest number of genes. Association of known gene defects with novel phenotypes and mode of inheritance were established. Electronic supplementary material The online version of this article (doi:10.1186/s13023-015-0300-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elise Boulanger-Scemama
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France
| | - Said El Shamieh
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France
| | - Vanessa Démontant
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France
| | - Christel Condroyer
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France
| | - Aline Antonio
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France.,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, DHU ViewMaintain, INSERM-DHOS CIC 1423, Paris, F-75012, France
| | - Christelle Michiels
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France
| | - Fiona Boyard
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France
| | - Jean-Paul Saraiva
- IntegraGen SA, Genopole CAMPUS 1 bat G8 FR-91030 EVRY, Paris, France
| | - Mélanie Letexier
- IntegraGen SA, Genopole CAMPUS 1 bat G8 FR-91030 EVRY, Paris, France
| | - Eric Souied
- Centre Hospitalier Intercommunal de Créteil, Department of Ophthalmology, Université Paris-Est Créteil, 94000, Créteil, France
| | - Saddek Mohand-Saïd
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France.,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, DHU ViewMaintain, INSERM-DHOS CIC 1423, Paris, F-75012, France
| | - José-Alain Sahel
- INSERM, U968, Paris, F-75012, France.,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France.,CNRS, UMR_7210, Paris, F-75012, France.,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, DHU ViewMaintain, INSERM-DHOS CIC 1423, Paris, F-75012, France.,Fondation Ophtalmologique Adolphe de Rothschild, 75019, Paris, France.,Académie des Sciences-Institut de France, 75006, Paris, France.,University College London Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK
| | - Christina Zeitz
- INSERM, U968, Paris, F-75012, France. .,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France. .,CNRS, UMR_7210, Paris, F-75012, France.
| | - Isabelle Audo
- INSERM, U968, Paris, F-75012, France. .,Institut de la Vision, Sorbonne Universités, UPMC Univ Paris 06, UMR_S 968, 17, rue Moreau, Paris, F-75012, France. .,CNRS, UMR_7210, Paris, F-75012, France. .,Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts, DHU ViewMaintain, INSERM-DHOS CIC 1423, Paris, F-75012, France. .,University College London Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK.
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19
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Zernant J, Collison FT, Lee W, Fishman GA, Noupuu K, Yuan B, Cai C, Lupski JR, Yannuzzi LA, Tsang SH, Allikmets R. Genetic and clinical analysis of ABCA4-associated disease in African American patients. Hum Mutat 2015; 35:1187-94. [PMID: 25066811 PMCID: PMC4283973 DOI: 10.1002/humu.22626] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 06/25/2014] [Indexed: 12/30/2022]
Abstract
Autosomal recessive Stargardt disease (STGD1) is caused by hundreds of mutations in the ABCA4 gene, which are often specific to racial and ethnic groups. Here, we investigated the ABCA4 variation and their phenotypic expression in a cohort of 44 patients of African American descent, a previously under-characterized racial group. Patients were screened for mutations in ABCA4 by next-generation sequencing and array-comparative genomic hybridization (aCGH), followed by analyses for pathogenicity by in silico programs. Thorough ophthalmic examination was performed on all patients. At least two (expected) disease-causing alleles in the ABCA4 gene were identified in 27 (61.4%) patients, one allele in 11 (25%) patients, and no ABCA4 mutations were found in six (13.6%) patients. Altogether, 39 different disease-causing ABCA4 variants, including seven new, were identified on 65 (74%) chromosomes, most of which were unique for this racial group. The most frequent ABCA4 mutation in this cohort was c.6320G>A (p.(R2107H)), representing 19.3% of all disease-associated alleles. No large copy number variants were identified in any patient. Most patients reported later onset of symptoms. In summary, the ABCA4 mutation spectrum in patients of West African descent differs significantly from that in patients of European descent, resulting in a later onset and "milder" disease.
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Affiliation(s)
- Jana Zernant
- Department of Ophthalmology, Columbia University, New York, New York
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20
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Clinical Utility Gene Card for: autosomal recessive cone-rod dystrophy. Eur J Hum Genet 2015; 23:ejhg201567. [PMID: 25873014 DOI: 10.1038/ejhg.2015.67] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 03/05/2015] [Accepted: 03/20/2015] [Indexed: 11/08/2022] Open
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21
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Zernant J, Xie YA, Ayuso C, Riveiro-Alvarez R, Lopez-Martinez MA, Simonelli F, Testa F, Gorin MB, Strom SP, Bertelsen M, Rosenberg T, Boone PM, Yuan B, Ayyagari R, Nagy PL, Tsang SH, Gouras P, Collison FT, Lupski JR, Fishman GA, Allikmets R. Analysis of the ABCA4 genomic locus in Stargardt disease. Hum Mol Genet 2014; 23:6797-806. [PMID: 25082829 DOI: 10.1093/hmg/ddu396] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Autosomal recessive Stargardt disease (STGD1, MIM 248200) is caused by mutations in the ABCA4 gene. Complete sequencing of ABCA4 in STGD patients identifies compound heterozygous or homozygous disease-associated alleles in 65-70% of patients and only one mutation in 15-20% of patients. This study was designed to find the missing disease-causing ABCA4 variation by a combination of next-generation sequencing (NGS), array-Comparative Genome Hybridization (aCGH) screening, familial segregation and in silico analyses. The entire 140 kb ABCA4 genomic locus was sequenced in 114 STGD patients with one known ABCA4 exonic mutation revealing, on average, 200 intronic variants per sample. Filtering of these data resulted in 141 candidates for new mutations. Two variants were detected in four samples, two in three samples, and 20 variants in two samples, the remaining 117 new variants were detected only once. Multimodal analysis suggested 12 new likely pathogenic intronic ABCA4 variants, some of which were specific to (isolated) ethnic groups. No copy number variation (large deletions and insertions) was detected in any patient suggesting that it is a very rare event in the ABCA4 locus. Many variants were excluded since they were not conserved in non-human primates, were frequent in African populations and, therefore, represented ancestral, and not disease-associated, variants. The sequence variability in the ABCA4 locus is extensive and the non-coding sequences do not harbor frequent mutations in STGD patients of European-American descent. Defining disease-associated alleles in the ABCA4 locus requires exceptionally well characterized large cohorts and extensive analyses by a combination of various approaches.
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Affiliation(s)
| | | | - Carmen Ayuso
- Department of Genetics, Instituto de Investigacion Sanitaria-University Hospital Fundacion Jimenez Diaz, UAM (IIS-FJD), Madrid, Spain Centro de Investigacion Biomedica en Red (CIBER) de Enfermedades Raras, ISCIII, Madrid, Spain
| | - Rosa Riveiro-Alvarez
- Department of Genetics, Instituto de Investigacion Sanitaria-University Hospital Fundacion Jimenez Diaz, UAM (IIS-FJD), Madrid, Spain Centro de Investigacion Biomedica en Red (CIBER) de Enfermedades Raras, ISCIII, Madrid, Spain
| | - Miguel-Angel Lopez-Martinez
- Department of Genetics, Instituto de Investigacion Sanitaria-University Hospital Fundacion Jimenez Diaz, UAM (IIS-FJD), Madrid, Spain Centro de Investigacion Biomedica en Red (CIBER) de Enfermedades Raras, ISCIII, Madrid, Spain
| | - Francesca Simonelli
- Eye Clinic, Multidisciplinary Department of Medical, Surgical and Dental Sciences, Second University of Naples, Naples, Italy
| | - Francesco Testa
- Eye Clinic, Multidisciplinary Department of Medical, Surgical and Dental Sciences, Second University of Naples, Naples, Italy
| | - Michael B Gorin
- Department of Ophthalmology Department of Human Genetics, Jules Stein Eye Institute and
| | - Samuel P Strom
- Department of Ophthalmology Department of Human Genetics, Jules Stein Eye Institute and Department of Pathology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Mette Bertelsen
- Kennedy Center Eye Clinic, Glostrup Hospital, Glostrup, Denmark
| | | | - Philip M Boone
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Bo Yuan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Radha Ayyagari
- Department of Ophthalmology, University of California San Diego, La Jolla, CA, USA and
| | - Peter L Nagy
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Stephen H Tsang
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | | | - Frederick T Collison
- The Pangere Center for Hereditary Retinal Diseases, The Chicago Lighthouse for People Who are Blind or Visually Impaired, Chicago, IL, USA
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Gerald A Fishman
- The Pangere Center for Hereditary Retinal Diseases, The Chicago Lighthouse for People Who are Blind or Visually Impaired, Chicago, IL, USA
| | - Rando Allikmets
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
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22
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Nagamani SCS, Erez A, Ben-Zeev B, Frydman M, Winter S, Zeller R, El-Khechen D, Escobar L, Stankiewicz P, Patel A, Cheung SW. Detection of copy-number variation in AUTS2 gene by targeted exonic array CGH in patients with developmental delay and autistic spectrum disorders. Eur J Hum Genet 2012; 21:343-6. [PMID: 22872102 DOI: 10.1038/ejhg.2012.157] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Small genomic rearrangements and copy-number variations (CNVs) involving a single gene have been associated recently with many neurocognitive phenotypes, including intellectual disability (ID), behavioral abnormalities, and autistic spectrum disorders (ASDs). Such small CNVs in the Autism susceptibility candidate 2 (AUTS2) gene have been shown to be associated with seizures, ID, and ASDs. We report four patients with small CNVs ranging in size between 133-319 kb that disrupt AUTS2. Two patients have duplications involving single exons, whereas two have deletions that removed multiple exons. All patients had developmental delay, whereas two patients had a diagnosis of ASDs. The CNVs were detected by an exon-targeted array CGH with dense oligonucleotide coverage in exons of genes known or hypothesized to be causative of multiple human phenotypes. Our report further shows that disruption of AUTS2 results in a variety of neurobehavioral phenotypes. More importantly, it demonstrates the utility of targeted exon array as a highly sensitive clinical diagnostic tool for the detection of small genomic rearrangements in the clinically relevant regions of the human genome.
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Affiliation(s)
- Sandesh C S Nagamani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
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23
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Lennon CJ, Birkeland AC, Nuñez JAP, Su GH, Lanzano P, Guzman E, Celis K, Eisig SB, Hoffman D, Rendon MTG, Ostos H, Chung WK, Haddad J. Association of candidate genes with nonsyndromic clefts in Honduran and Colombian populations. Laryngoscope 2012; 122:2082-7. [DOI: 10.1002/lary.23394] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2012] [Revised: 03/14/2012] [Accepted: 03/28/2012] [Indexed: 11/10/2022]
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24
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Zernant J, Schubert C, Im KM, Burke T, Brown CM, Fishman GA, Tsang SH, Gouras P, Dean M, Allikmets R. Analysis of the ABCA4 gene by next-generation sequencing. Invest Ophthalmol Vis Sci 2011; 52:8479-87. [PMID: 21911583 DOI: 10.1167/iovs.11-8182] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
PURPOSE To find all possible disease-associated variants in coding sequences of the ABCA4 gene in a large cohort of patients diagnosed with ABCA4-associated diseases. METHODS One hundred sixty-eight patients who had been clinically diagnosed with Stargardt disease, cone-rod dystrophy, and other ABCA4-associated phenotypes were prescreened for mutations in ABCA4 with the ABCA4 microarray, resulting in finding 1 of 2 expected mutations in 111 patients and 0 of 2 mutations in 57 patients. The next-generation sequencing (NGS) strategy was applied to these patients to sequence the entire coding region and the splice sites of the ABCA4 gene. Identified new variants were confirmed or rejected by Sanger sequencing and analyzed for possible pathogenicity by in silico programs and, where possible, by segregation analyses. RESULTS Sequencing was successful in 159 of 168 patients and identified the second disease-associated allele in 49 of 103 (~48%) of patients with one previously identified mutation. Among those with no mutations, both disease-associated alleles were detected in 4 of 56 patients, and one mutation was detected in 10 of 56 patients. The authors detected a total of 57 previously unknown, possibly pathogenic, variants: 29 missense, 4 nonsense, 9 small deletions and 15 splice-site-altering variants. Of these, 55 variants were deemed pathogenic by a combination of predictive methods and segregation analyses. CONCLUSIONS Many mutations in the coding sequences of the ABCA4 gene are still unknown, and many possibly reside in noncoding regions of the ABCA4 locus. Although the ABCA4 array remains a good first-pass screening option, the NGS platform is a time- and cost-efficient tool for screening large cohorts.
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Affiliation(s)
- Jana Zernant
- Department of Ophthalmology, Columbia University, New York, New York 10032, USA
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25
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Boone PM, Bacino CA, Shaw CA, Eng PA, Hixson PM, Pursley AN, Kang SHL, Yang Y, Wiszniewska J, Nowakowska BA, del Gaudio D, Xia Z, Simpson-Patel G, Immken LL, Gibson JB, Tsai ACH, Bowers JA, Reimschisel TE, Schaaf CP, Potocki L, Scaglia F, Gambin T, Sykulski M, Bartnik M, Derwinska K, Wisniowiecka-Kowalnik B, Lalani SR, Probst FJ, Bi W, Beaudet AL, Patel A, Lupski JR, Cheung SW, Stankiewicz P. Detection of clinically relevant exonic copy-number changes by array CGH. Hum Mutat 2010; 31:1326-42. [PMID: 20848651 DOI: 10.1002/humu.21360] [Citation(s) in RCA: 201] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2010] [Accepted: 09/02/2010] [Indexed: 12/22/2022]
Abstract
Array comparative genomic hybridization (aCGH) is a powerful tool for the molecular elucidation and diagnosis of disorders resulting from genomic copy-number variation (CNV). However, intragenic deletions or duplications--those including genomic intervals of a size smaller than a gene--have remained beyond the detection limit of most clinical aCGH analyses. Increasing array probe number improves genomic resolution, although higher cost may limit implementation, and enhanced detection of benign CNV can confound clinical interpretation. We designed an array with exonic coverage of selected disease and candidate genes and used it clinically to identify losses or gains throughout the genome involving at least one exon and as small as several hundred base pairs in size. In some patients, the detected copy-number change occurs within a gene known to be causative of the observed clinical phenotype, demonstrating the ability of this array to detect clinically relevant CNVs with subkilobase resolution. In summary, we demonstrate the utility of a custom-designed, exon-targeted oligonucleotide array to detect intragenic copy-number changes in patients with various clinical phenotypes.
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Affiliation(s)
- Philip M Boone
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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26
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Abstract
The blood-brain barrier (BBB) is a dynamic physical and biological barrier between blood circulation and the central nervous system (CNS). This unique feature of the BBB lies in the structure of the neurovascular unit and its cerebral micro-vascular endothelial cells. The BBB restricts the passage of blood-borne drugs, neurotoxic substances and peripheral immune cells from entering the brain, while selectively facilitating the transport of nutrients across the BBB into the brain. Thus, the integrity and proper function of the BBB is crucial to homeostasis and physiological function of the CNS. A number of transport and carrier systems are expressed and polarized on the luminal or abluminal surface of the BBB to realize these discrete functions. Among these systems, ABC transporters play a critical role in keeping drugs and neurotoxic substances from entering the brain and in transporting toxic metabolites out of the brain. A number of studies have demonstrated that ABCB1 and ABCG2 are critical to drug efflux at the BBB and that ABCC1 is essential for the blood-cerebral spinal fluid (CSF) barrier. The presence of these efflux ABC transporters also creates a major obstacle for drug delivery into the brain. We have comprehensively reviewed the literature on ABC transporters and drug efflux at the BBB. Understanding the molecular mechanisms of these transporters is important in the development of new drugs and new strategies for drug delivery into the brain.
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Affiliation(s)
- Shanshan Shen
- Neurobiology Program, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Canada K1A 0R6
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27
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Stenirri S, Alaimo G, Manitto MP, Brancato R, Ferrari M, Cremonesi L. Are microarrays useful in the screening of ABCA4 mutations in Italian patients affected by macular degenerations? Clin Chem Lab Med 2008; 46:1250-5. [PMID: 18652558 DOI: 10.1515/cclm.2008.248] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Recessive Stargardt disease is due to mutation in the retina-specific ABC transporter gene. Established strategies for molecular characterization of this gene include direct detection by a microarray interrogating approximately 500 DNA variations and a scanning denaturing HPLC methodology. METHODS Because 11 mutations were recorded to account for approximately 50% of molecular defects in the Italian population, we evaluated an alternative open microchip-based assay for a fast and simplified level 1 screening for these mutations. RESULTS This approach allowed the characterization of both mutated alleles in 4% and one mutated allele in 43% of cases when applied to a cohort of 47 Stargardt patients. In the same patients, further investigation by denaturing HPLC for complete characterization identified both mutated allele in 51% and one mutated allele in 19% of cases, allowing the detection of 38 different mutations, five of which had never been described. Notably, new mutations account for a high proportion (13%) of molecular defects in our patient cohort. CONCLUSION The findings raises the question about the choice of the optimal diagnostic strategy for complete genotyping of the ABCA4 gene, as new mutations could not be identified by any direct detection technology, irrespective of the total number of variations screened.
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Affiliation(s)
- Stefania Stenirri
- Genomic Unit for the Diagnosis of Human Pathologies, San Raffaele Scientific Institute, Milan, Italy
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28
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Yatsenko AN, Wiszniewski W, Zaremba CM, Jamrich M, Lupski JR. Evolution of ABCA4 proteins in vertebrates. J Mol Evol 2005; 60:72-80. [PMID: 15696369 DOI: 10.1007/s00239-004-0118-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Accepted: 08/10/2004] [Indexed: 11/29/2022]
Abstract
The ABCA4 (ABCR) gene encodes a retinal-specific ATP-binding cassette transporter. Mutations in ABCA4 are responsible for several recessive macular dystrophies and susceptibility to age related macular degeneration (AMD). The protein appears to function as a flippase of all-trans-retinaldehyde and/or its derivatives across the membrane of outer segment disks and is a potentially important element in recycling visual cycle metabolites. However, the understanding of ABCA4's role in the visual cycle is limited due to the lack of a direct functional assay. An evolutionary analysis of ABCA4 may aid in the identification of conserved elements, the preservation of which implies functional importance. To date, only human, murine, and bovine ABCA4 genes are described. We have identified ABCA4 genes from African (Xenopus laevis) and Western (Silurana tropicalis) clawed frogs. A comparative analysis describing the evolutionary relationships between the frog ABCA4s, annotated T. rubripes ABCA4, and mammalian ABCA4 proteins was carried out. Several segments are conserved in both intradiscal loop (IL) domains, in addition to the transmembrane and ATP-binding domains. Nonconserved segments were found in the IL and cytoplasmic linker domains. Maximum likelihood analyses of the aligned sequences strongly suggest that ABCA4 was subject to purifying selection. Collectively, these data corroborate the current evolutionary model where two distinct ABCA half-transporter progenitors were combined to form a full ABCA4 progenitor in ancestral chordates. We speculate that evolutionary alterations may increase the retinoid metabolite recycling capacity of ABCA4 and may improve dark adaptation.
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Affiliation(s)
- Alexander N Yatsenko
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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29
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Cideciyan AV, Aleman TS, Swider M, Schwartz SB, Steinberg JD, Brucker AJ, Maguire AM, Bennett J, Stone EM, Jacobson SG. Mutations in ABCA4 result in accumulation of lipofuscin before slowing of the retinoid cycle: a reappraisal of the human disease sequence. Hum Mol Genet 2004; 13:525-34. [PMID: 14709597 DOI: 10.1093/hmg/ddh048] [Citation(s) in RCA: 192] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mutations in ABCA4, which encodes a photoreceptor specific ATP-binding cassette transporter (ABCR), cause autosomal recessive forms of human blindness due to retinal degeneration (RD) including Stargardt disease. The exact disease sequence leading to photoreceptor and vision loss in ABCA4-RD is not known. Extrapolation from murine and in vitro studies predicts that two of the earliest pathophysiological features resulting from disturbed ABCR function in man would be slowed kinetics of the retinoid cycle and accelerated deposition of lipofuscin in the retinal pigment epithelium (RPE). To determine the human pathogenetic sequence, we studied surrogate measures of retinoid cycle kinetics, lipofuscin accumulation, and rod and cone photoreceptor and RPE loss in ABCA4-RD patients with a wide spectrum of disease severities. There were different extents of photoreceptor/RPE loss and lipofuscin accumulation in different regions of the retina. Slowing of retinoid cycle kinetics was not present in all patients; when present, it was not homogeneous across the retina; and the extent of slowing correlated well with the degree of degeneration. The orderly relationship between these phenotypic features permitted the development of a model of disease sequence in ABCA4-RD. The model predicted lipofuscin accumulation as a key and early component of the disease expression in man, as in mice. In man, however, abnormal slowing of the rod and cone retinoid cycle occurs at later stages of the disease sequence. Knowledge of the human ABCA4 disease sequence will be critical for defining rates of progression, selecting appropriate patients and retinal locations for future therapy, and choosing appropriate treatment outcomes.
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Affiliation(s)
- Artur V Cideciyan
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA 19104, USA.
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