1
|
Molecular analysis of ABCA4 gene in an Iranian cohort with Stargardt disease. GENE REPORTS 2022. [DOI: 10.1016/j.genrep.2021.101450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
2
|
Molday RS, Garces FA, Scortecci JF, Molday LL. Structure and function of ABCA4 and its role in the visual cycle and Stargardt macular degeneration. Prog Retin Eye Res 2021; 89:101036. [PMID: 34954332 DOI: 10.1016/j.preteyeres.2021.101036] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 12/07/2021] [Accepted: 12/13/2021] [Indexed: 12/17/2022]
Abstract
ABCA4 is a member of the superfamily of ATP-binding cassette (ABC) transporters that is preferentially localized along the rim region of rod and cone photoreceptor outer segment disc membranes. It uses the energy from ATP binding and hydrolysis to transport N-retinylidene-phosphatidylethanolamine (N-Ret-PE), the Schiff base adduct of retinal and phosphatidylethanolamine, from the lumen to the cytoplasmic leaflet of disc membranes. This ensures that all-trans-retinal and excess 11-cis-retinal are efficiently cleared from photoreceptor cells thereby preventing the accumulation of toxic retinoid compounds. Loss-of-function mutations in the gene encoding ABCA4 cause autosomal recessive Stargardt macular degeneration, also known as Stargardt disease (STGD1), and related autosomal recessive retinopathies characterized by impaired central vision and an accumulation of lipofuscin and bis-retinoid compounds. High resolution structures of ABCA4 in its substrate and nucleotide free state and containing bound N-Ret-PE or ATP have been determined by cryo-electron microscopy providing insight into the molecular architecture of ABCA4 and mechanisms underlying substrate recognition and conformational changes induced by ATP binding. The expression and functional characterization of a large number of disease-causing missense ABCA4 variants have been determined. These studies have shed light into the molecular mechanisms underlying Stargardt disease and a classification that reliably predicts the effect of a specific missense mutation on the severity of the disease. They also provide a framework for developing rational therapeutic treatments for ABCA4-associated diseases.
Collapse
Affiliation(s)
- Robert S Molday
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, B.C., Canada; Department of Ophthalmology & Visual Sciences, University of British Columbia, Vancouver, B.C., Canada.
| | - Fabian A Garces
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, B.C., Canada
| | | | - Laurie L Molday
- Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, B.C., Canada
| |
Collapse
|
3
|
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: 19] [Impact Index Per Article: 6.3] [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.
Collapse
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.)
| |
Collapse
|
4
|
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
| |
Collapse
|
5
|
Mena MD, Moresco AA, Vidal SH, Aguilar-Cortes D, Obregon MG, Fandiño AC, Sendoya JM, Llera AS, Podhajcer OL. Clinical and Genetic Spectrum of Stargardt Disease in Argentinean Patients. Front Genet 2021; 12:646058. [PMID: 33841504 PMCID: PMC8033171 DOI: 10.3389/fgene.2021.646058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Accepted: 03/05/2021] [Indexed: 12/11/2022] Open
Abstract
Purpose To describe the clinical and molecular spectrum of Stargardt disease (STGD) in a cohort of Argentinean patients. Methods This retrospective study included 132 subjects comprising 95 probands clinically diagnosed with STGD and relatives from 16 of them. Targeted next-generation sequencing of the coding and splicing regions of ABCA4 and other phenocopying genes (ELOVL4, PROM1, and CNGB3) was performed in 97 STGD patients. Results We found two or more disease-causing variants in the ABCA4 gene in 69/95 (73%) probands, a single ABCA4 variant in 9/95 (9.5%) probands, and no ABCA4 variants in 17/95 (18%) probands. The final analysis identified 173 variants in ABCA4. Seventy-nine ABCA4 variants were unique, of which nine were novel. No significant findings were seen in the other evaluated genes. Conclusion This study describes the phenotypic and genetic features of STGD1 in an Argentinean cohort. The mutations p.(Gly1961Glu) and p.(Arg1129Leu) were the most frequent, representing almost 20% of the mutated alleles. We also expanded the ABCA4 mutational spectrum with nine novel disease-causing variants, of which eight might be associated with South American natives.
Collapse
Affiliation(s)
- Marcela D Mena
- Laboratorio de Terapia Molecular y Celular (Genocan), Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| | - Angélica A Moresco
- Servicio de Genética, Hospital de Pediatría Prof. Dr. Juan P. Garrahan, Buenos Aires, Argentina
| | - Sofía H Vidal
- Servicio de Oftalmología, Hospital de Pediatría Prof. Dr. Juan P. Garrahan, Buenos Aires, Argentina
| | - Diana Aguilar-Cortes
- Laboratorio de Terapia Molecular y Celular (Genocan), Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| | - María G Obregon
- Servicio de Genética, Hospital de Pediatría Prof. Dr. Juan P. Garrahan, Buenos Aires, Argentina
| | - Adriana C Fandiño
- Servicio de Oftalmología, Hospital de Pediatría Prof. Dr. Juan P. Garrahan, Buenos Aires, Argentina
| | - Juan M Sendoya
- Laboratorio de Terapia Molecular y Celular (Genocan), Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| | - Andrea S Llera
- Laboratorio de Terapia Molecular y Celular (Genocan), Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| | - Osvaldo L Podhajcer
- Laboratorio de Terapia Molecular y Celular (Genocan), Fundación Instituto Leloir, CONICET, Buenos Aires, Argentina
| |
Collapse
|
6
|
Collison FT, Lee W, Fishman GA, Park JC, Zernant J, McAnany JJ, Allikmets R. CLINICAL CHARACTERIZATION OF STARGARDT DISEASE PATIENTS WITH THE p.N1868I ABCA4 MUTATION. Retina 2020; 39:2311-2325. [PMID: 30204727 DOI: 10.1097/iae.0000000000002316] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To investigate the Stargardt disease phenotype associated with an unusually common and "extremely hypomorphic" ABCA4 variant, p.N1868I. METHODS The charts of 27 patients with p.N1868I on one allele and a severe/deleterious mutation on the other allele were reviewed. Subjective age of onset, best-corrected visual acuity, and stage of disease were recorded for all 27 patients, 18 of whom had multiple visits. When available, fundus photography, spectral domain optical coherence tomography, fundus autofluorescence, full-field electroretinograms, Goldmann visual fields, and fluorescein angiography were included. Five families with multiple affected members were analyzed. RESULTS The median age at symptom onset was 41.5 years, and 3 p.N1868I patients had not developed visual symptoms as of the most recent eye examination. Median best-corrected visual acuity in the better-seeing eye at baseline was 20/25, and the median duration from symptom onset to legal blindness was 25 years. The five families described in this study demonstrated clinically significant intrafamilial variability, and affected family members who did not share the p.N1868I variant had relatively more severe phenotypes. CONCLUSION This study demonstrates the consistency of foveal sparing, the variation in age at onset, the intrafamilial variability, and the prognosis with regard to visual acuity in p.N1868I-associated Stargardt disease.
Collapse
Affiliation(s)
- Frederick T Collison
- The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois
| | - Winston Lee
- Department of Ophthalmology, Columbia University, New York, New York
| | - Gerald A Fishman
- The Pangere Center for Inherited Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois.,Department of Ophthalmology and Visual Sciences, The University of Illinois at Chicago, Chicago, Illinois
| | - Jason C Park
- Department of Ophthalmology and Visual Sciences, The University of Illinois at Chicago, Chicago, Illinois
| | - Jana Zernant
- Department of Ophthalmology, Columbia University, New York, New York
| | - J Jason McAnany
- Department of Ophthalmology and Visual Sciences, The University of Illinois at Chicago, Chicago, Illinois
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, New York.,Department of Pathology and Cell Biology, Columbia University, New York, New York
| |
Collapse
|
7
|
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: 155] [Impact Index Per Article: 38.8] [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.
Collapse
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.
| |
Collapse
|
8
|
Allikmets R, Zernant J, Lee W. Penetrance of the ABCA4 p.Asn1868Ile Allele in Stargardt Disease. Invest Ophthalmol Vis Sci 2019; 59:5564-5565. [PMID: 30480703 PMCID: PMC6735614 DOI: 10.1167/iovs.18-25579] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Rando Allikmets
- Departments of Ophthalmology, Columbia University, New York, New York, United States.,Pathology & Cell Biology, Columbia University, New York, New York, United States
| | - Jana Zernant
- Departments of Ophthalmology, Columbia University, New York, New York, United States
| | - Winston Lee
- Departments of Ophthalmology, Columbia University, New York, New York, United States
| |
Collapse
|
9
|
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: 45] [Impact Index Per Article: 9.0] [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.
Collapse
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
| |
Collapse
|
10
|
Interpretation of Genomic Sequencing Results in Healthy and Ill Newborns: Results from the BabySeq Project. Am J Hum Genet 2019; 104:76-93. [PMID: 30609409 DOI: 10.1016/j.ajhg.2018.11.016] [Citation(s) in RCA: 147] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 11/23/2018] [Indexed: 12/27/2022] Open
Abstract
Genomic sequencing provides many opportunities in newborn clinical care, but the challenges of interpreting and reporting newborn genomic sequencing (nGS) results need to be addressed for its broader and effective application. The BabySeq Project is a pilot randomized clinical trial that explores the medical, behavioral, and economic impacts of nGS in well newborns and those admitted to a neonatal intensive care unit (NICU). Here we present childhood-onset and actionable adult-onset disease risk, carrier status, and pharmacogenomics findings from nGS of 159 newborns in the BabySeq Project. nGS revealed a risk of childhood-onset disease in 15/159 (9.4%) newborns; none of the disease risks were anticipated based on the infants' known clinical or family histories. nGS also revealed actionable adult-onset disease risk in 3/85 (3.5%) newborns whose parents consented to receive this information. Carrier status for recessive diseases and pharmacogenomics variants were reported in 88% and 5% of newborns, respectively. Additional indication-based analyses were performed in 29/32 (91%) NICU newborns and 6/127 (5%) healthy newborns who later had presentations that prompted a diagnostic analysis. No variants that sufficiently explained the reason for the indications were identified; however, suspicious but uncertain results were reported in five newborns. Testing parental samples contributed to the interpretation and reporting of results in 13/159 (8%) newborns. Our results suggest that nGS can effectively detect risk and carrier status for a wide range of disorders that are not detectable by current newborn screening assays or predicted based on the infant's known clinical or family history, and the interpretation of results can substantially benefit from parental testing.
Collapse
|
11
|
Stenirri S, Battistella S, Soriani N, Bernal S, Baiget M, Ferrari M, Cremonesi L. Molecular Scanning of the ABCA4 Gene in Spanish Patients with Retinitis Pigmentosa and Stargardt Disease: Identification of Novel Mutations. Eur J Ophthalmol 2018; 17:749-54. [DOI: 10.1177/112067210701700510] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- S. Stenirri
- Genomic Unit for Diagnosis of Human Pathologies, San Raffaele Scientific Institute, Milano - Italy
| | - S. Battistella
- Genomic Unit for Diagnosis of Human Pathologies, San Raffaele Scientific Institute, Milano - Italy
| | - N. Soriani
- Genomic Unit for Diagnosis of Human Pathologies, San Raffaele Scientific Institute, Milano - Italy
| | - S. Bernal
- Servei de Genètica, Hospital Sant Pau, Barcelona - Spain
| | - M. Baiget
- Servei de Genètica, Hospital Sant Pau, Barcelona - Spain
| | - M. Ferrari
- Genomic Unit for Diagnosis of Human Pathologies, San Raffaele Scientific Institute, Milano - Italy
- Diagnostica e Ricerca San Raffaele SpA, Milano
- Università Vita-Salute San Raffaele, Milano - Italy
| | - L. Cremonesi
- Genomic Unit for Diagnosis of Human Pathologies, San Raffaele Scientific Institute, Milano - Italy
| |
Collapse
|
12
|
Zernant J, Lee W, Collison FT, Fishman GA, Sergeev YV, Schuerch K, Sparrow JR, Tsang SH, Allikmets R. Frequent hypomorphic alleles account for a significant fraction of ABCA4 disease and distinguish it from age-related macular degeneration. J Med Genet 2017; 54:404-412. [PMID: 28446513 DOI: 10.1136/jmedgenet-2017-104540] [Citation(s) in RCA: 116] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 02/28/2017] [Accepted: 03/07/2017] [Indexed: 12/24/2022]
Abstract
BACKGROUND Variation in the ABCA4 gene is causal for, or associated with, a wide range of phenotypes from early onset Mendelian retinal dystrophies to late-onset complex disorders such as age-related macular degeneration (AMD). Despite substantial progress in determining the causal genetic variation, even complete sequencing of the entire open reading frame and splice sites of ABCA4 identifies biallelic mutations in only 60%-70% of cases; 20%-25% remain with one mutation and no mutations are found in 10%-15% of cases with clinically confirmed ABCA4 disease. This study was designed to identify missing causal variants specifically in monoallelic cases of ABCA4 disease. METHODS Direct sequencing and analysis were performed in a large familial ABCA4 disease cohort of predominately European descent (n=643). Patient phenotypes were assessed from clinical and retinal imaging data. RESULTS We determined that a hypomorphic ABCA4 variant c.5603A>T (p.Asn1868Ile), previously considered benign due to high minor allele frequency (MAF) (~7%) in the general population, accounts for 10% of the disease, >50% of the missing causal alleles in monoallelic cases, ~80% of late-onset cases and distinguishes ABCA4 disease from AMD. It results in a distinct clinical phenotype characterised by late-onset of symptoms (4th decade) and foveal sparing (85%). Intragenic modifying effects involving this variant and another, c.2588G>C (p.Gly863Ala) allele, were also identified. CONCLUSIONS These findings substantiate the causality of frequent missense variants and their phenotypic outcomes as a significant contribution to ABCA4 disease, particularly the late-onset phenotype, and its clinical variation. They also suggest a significant revision of diagnostic screening and assessment of ABCA4 variation in aetiology of retinal diseases.
Collapse
Affiliation(s)
- Jana Zernant
- Department of Ophthalmology, Columbia University, New York, New York, USA
| | - Winston Lee
- Department of Ophthalmology, Columbia University, New York, New York, USA
| | - Frederick T Collison
- The Pangere Center for Hereditary Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois, USA
| | - Gerald A Fishman
- The Pangere Center for Hereditary Retinal Diseases, The Chicago Lighthouse, Chicago, Illinois, USA
| | - Yuri V Sergeev
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Kaspar Schuerch
- Department of Ophthalmology, Columbia University, New York, New York, USA
| | - Janet R Sparrow
- Department of Ophthalmology, Columbia University, New York, New York, USA.,Department of Pathology & Cell Biology, Columbia University, New York, New York, USA
| | - Stephen H Tsang
- Department of Ophthalmology, Columbia University, New York, New York, USA.,Department of Pathology & Cell Biology, Columbia University, New York, New York, USA
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, New York, USA.,Department of Pathology & Cell Biology, Columbia University, New York, New York, USA
| |
Collapse
|
13
|
Yusuf IH, Sharma S, Luqmani R, Downes SM. Hydroxychloroquine retinopathy. Eye (Lond) 2017; 31:828-845. [PMID: 28282061 DOI: 10.1038/eye.2016.298] [Citation(s) in RCA: 141] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 08/24/2016] [Indexed: 12/16/2022] Open
Abstract
Hydroxychloroquine (HCQ; Plaquenil) is used increasingly in the management of a variety of autoimmune disorders, with well established roles in dermatology and rheumatology and emerging roles in oncology. Hydroxychloroquine has demonstrated a survival benefit in patients with systemic lupus erythematosus; some clinicians advocate its use in all such patients. However, Hydroxychloroquine and chloroquine (CQ) have been associated with irreversible visual loss due to retinal toxicity. Hydroxychloroquine retinal toxicity is far more common than previously considered; an overall prevalence of 7.5% was identified in patients taking HCQ for greater than 5 years, rising to almost 20% after 20 years of treatment. This review aims to provide an update on HCQ/CQ retinopathy. We summarise emerging treatment indications and evidence of efficacy in systemic disease, risk factors for retinopathy, prevalence among HCQ users, diagnostic tests, and management of HCQ retinopathy. We highlight emerging risk factors such as tamoxifen use, and new guidance on safe dosing, reversing the previous recommendation to use ideal body weight, rather than actual body weight. We summarise uncertainties and the recommendations made by existing HCQ screening programmes. Asian patients with HCQ retinopathy may demonstrate an extramacular or pericentral pattern of disease; visual field testing and retinal imaging should include a wider field for screening in this group. HCQ is generally safe and effective for the treatment of systemic disease but because of the risk of HCQ retinal toxicity, modern screening methods and ideal dosing should be implemented. Guidelines regarding optimal dosing and screening regarding HCQ need to be more widely disseminated.
Collapse
Affiliation(s)
- I H Yusuf
- The Oxford Eye Hospital, West Wing, John Radcliffe Hospital, Oxford, UK
| | - S Sharma
- The Oxford Eye Hospital, West Wing, John Radcliffe Hospital, Oxford, UK
| | - R Luqmani
- Department of Rheumatology, Nuffield Orthopaedic Centre, Oxford, UK
| | - S M Downes
- The Oxford Eye Hospital, West Wing, John Radcliffe Hospital, Oxford, UK
| |
Collapse
|
14
|
Kaway CS, Adams MKM, Jenkins KS, Layton CJ. A Novel ABCA4 Mutation Associated with a Late-Onset Stargardt Disease Phenotype: A Hypomorphic Allele? Case Rep Ophthalmol 2017; 8:180-184. [PMID: 28611652 PMCID: PMC5465797 DOI: 10.1159/000464129] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 02/16/2017] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Stargardt disease (STGD) is the most common juvenile hereditary macular dystrophy. In the majority of cases, the diagnosis is made prior to 20 years of age and usually leads to loss of central vision. Late-onset STGD affects a smaller number of patients. Identifying genetic changes which could be associated with clinically important differences in severity or presentation of the disease is important for understanding the mechanisms of visual loss and for planning future therapeutic approaches. METHODS We report a patient with the classic phenotype of STGD with late-onset mild disease exhibiting a slow clinical progression over 14 months of follow-up. RESULTS A 37-year-old man presented with STGD and good vision of 6/24 in the right eye and of 6/6 in the left eye as well as typical electrophysiology findings. Objective and subjective visual deterioration was not noted over a period of 14 months. Macular genetic testing revealed a novel missense mutation in ABCA4 (Thr829Met) combined with Gly1961Glu, a classic STGD mutation usually associated with a moderately severe phenotype. CONCLUSIONS It is suggested that the Thr829Met mutation could give rise to a hypomorphic allele of the ABC transporter with a resultant phenotype of comparatively mild STGD.
Collapse
Affiliation(s)
| | - Madeleine K M Adams
- bGallipoli Medical Research Institute, Brisbane, Queensland, Australia.,cUniversity of Queensland School of Medicine, Herston, Queensland, Australia.,dGreenslopes Private Hospital Ophthalmology Department, Greenslopes Hospital, Brisbane, Queensland, Australia
| | - Kevin Sean Jenkins
- bGallipoli Medical Research Institute, Brisbane, Queensland, Australia.,cUniversity of Queensland School of Medicine, Herston, Queensland, Australia
| | - Christopher J Layton
- bGallipoli Medical Research Institute, Brisbane, Queensland, Australia.,cUniversity of Queensland School of Medicine, Herston, Queensland, Australia.,dGreenslopes Private Hospital Ophthalmology Department, Greenslopes Hospital, Brisbane, Queensland, Australia
| |
Collapse
|
15
|
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: 53] [Impact Index Per Article: 5.9] [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.
Collapse
Affiliation(s)
- Nathalie M Bax
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Presentation of Complex Homozygous Allele in ABCA4 Gene in a Patient with Retinitis Pigmentosa. Case Rep Ophthalmol Med 2015; 2015:452068. [PMID: 26229699 PMCID: PMC4503555 DOI: 10.1155/2015/452068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 06/08/2015] [Accepted: 06/17/2015] [Indexed: 11/17/2022] Open
Abstract
Retinitis pigmentosa is a degenerative retinal disease characterized by progressive photoreceptor damage, which causes loss of peripheral and night vision and the development of tunnel vision and may result in loss of central vision. This study describes a patient with retinitis pigmentosa caused by a mutation in the ABCA4 gene with complex allele c.1622T>C, p.L541P; c.3113C>T, p.A1038V in homozygous state.
Collapse
|
17
|
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
|
18
|
Bauwens M, De Zaeytijd J, Weisschuh N, Kohl S, Meire F, Dahan K, Depasse F, De Jaegere S, De Ravel T, De Rademaeker M, Loeys B, Coppieters F, Leroy BP, De Baere E. An AugmentedABCA4Screen Targeting Noncoding Regions Reveals a Deep Intronic Founder Variant in Belgian Stargardt Patients. Hum Mutat 2014; 36:39-42. [DOI: 10.1002/humu.22716] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 10/18/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Miriam Bauwens
- Center for Medical Genetics; Ghent University and Ghent University Hospital; Ghent Belgium
| | - Julie De Zaeytijd
- Department of Ophthalmology; Ghent University Hospital; Ghent Belgium
| | - Nicole Weisschuh
- Molecular Genetics Laboratory; Institute for Ophthalmic Research; Centre for Ophthalmology; University of Tuebingen; Tuebingen Germany
| | - Susanne Kohl
- Molecular Genetics Laboratory; Institute for Ophthalmic Research; Centre for Ophthalmology; University of Tuebingen; Tuebingen Germany
| | - Françoise Meire
- Department of Ophthalmology; Queen Fabiola Children's University Hospital; Brussels Belgium
| | - Karin Dahan
- Centre de génétique humaine; Institut de Pathologie et de Génétique; Gosselies Belgium
| | - Fanny Depasse
- Department of Ophthalmology; Queen Fabiola Children's University Hospital; Brussels Belgium
| | - Sarah De Jaegere
- Center for Medical Genetics; Ghent University and Ghent University Hospital; Ghent Belgium
| | - Thomy De Ravel
- Center for Human Genetics; Leuven University Hospitals; Leuven Belgium
| | | | - Bart Loeys
- Center for Medical Genetics; University of Antwerp and Antwerp University Hospital; Antwerp Belgium
| | - Frauke Coppieters
- Center for Medical Genetics; Ghent University and Ghent University Hospital; Ghent Belgium
| | - Bart P. Leroy
- Center for Medical Genetics; Ghent University and Ghent University Hospital; Ghent Belgium
- Department of Ophthalmology; Ghent University Hospital; Ghent Belgium
- Division of Ophthalmology; The Children's Hospital of Philadelphia; Philadelphia Pennsylvania
| | - Elfride De Baere
- Center for Medical Genetics; Ghent University and Ghent University Hospital; Ghent Belgium
| |
Collapse
|
19
|
Sisk RA, Leng T. Multimodal imaging and multifocal electroretinography demonstrate autosomal recessive Stargardt disease may present like occult macular dystrophy. Retina 2014; 34:1567-75. [PMID: 24743636 DOI: 10.1097/iae.0000000000000136] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To describe multimodal imaging and electrophysiologic characteristics of an unusual subset of patients with genetically confirmed autosomal recessive Stargardt disease (STGD1) who exhibited a central form of cone dysfunction resembling occult macular dystrophy that preceded the development of lipofuscin flecks, atrophy of retinal pigment epithelium (RPE), or full-field electroretinography abnormalities. METHODS Retrospective, observational descriptive case series. RESULTS Five patients with compound heterozygous ABCA4 mutations presented with bilateral visual acuity reduction, normal-appearing fundi, and blocked choroidal fluorescence on fluorescein angiography. One sibling each of two probands with identical genotypes was also included for analysis. Full-field electroretinography testing was normal in all patients, but multifocal electroretinography demonstrated centripetally depressed amplitudes exceeding areas of fundus autofluorescence, infrared imaging, and spectral domain optical coherence tomography abnormalities. Spectral domain optical coherence tomography initially revealed disruption of the inner segment ellipsoid band accompanying an ovoid hypofluorescent foveolar lesion. Progression to later stages was accompanied by the loss of the foveal photoreceptor outer segments, creating foveal cavitation with preservation of the RPE. Fundus autofluorescence and infrared imaging demonstrated corresponding bull's eye lesions. Over time, the foveal potential space on spectral domain optical coherence tomography collapsed, and three patients developed RPE atrophy and visible lipofuscin flecks. The flecks were detectable by fundus autofluorescence and infrared imaging earlier than by biomicroscopy. From these findings, a staging system for this subset of Stargardt disease presenting with central cone dysfunction was developed and presented herein. CONCLUSION Autosomal recessive Stargardt disease may present as a central cone dysfunction syndrome before the development of lipofuscin flecks, atrophy of RPE, or full-field electroretinography abnormalities. If emerging therapies for Stargardt disease succeed, early recognition and treatment of patients with preserved foveal photoreceptor and RPE cell bodies may yield a more favorable visual prognosis.
Collapse
Affiliation(s)
- Robert A Sisk
- *Cincinnati Eye Institute, Cincinnati, Ohio; †Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; ‡Department of Ophthalmology, University of Cincinnati, Cincinnati, Ohio; and §Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California
| | | |
Collapse
|
20
|
Lambertus S, van Huet RAC, Bax NM, Hoefsloot LH, Cremers FPM, Boon CJF, Klevering BJ, Hoyng CB. Early-onset stargardt disease: phenotypic and genotypic characteristics. Ophthalmology 2014; 122:335-44. [PMID: 25444351 DOI: 10.1016/j.ophtha.2014.08.032] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 07/16/2014] [Accepted: 08/14/2014] [Indexed: 10/24/2022] Open
Abstract
OBJECTIVE To describe the phenotype and genotype of patients with early-onset Stargardt disease. DESIGN Retrospective cohort study. PARTICIPANTS Fifty-one Stargardt patients with age at onset ≤10 years. METHODS We reviewed patient medical records for age at onset, medical history, initial symptoms, best-corrected visual acuity (BCVA), ophthalmoscopy, fundus photography, fundus autofluorescence (FAF), fluorescein angiography (FA), spectral-domain optical coherence tomography (SD-OCT), and full-field electroretinography (ffERG). The ABCA4 gene was screened for mutations. MAIN OUTCOME MEASURES Age at onset, BCVA, fundus appearance, FAF, FA, SD-OCT, ffERG, and presence of ABCA4 mutations. RESULTS The mean age at onset was 7.2 years (range, 1-10). The median times to develop BCVA of 20/32, 20/80, 20/200, and 20/500 were 3, 5, 12, and 23 years, respectively. Initial ophthalmoscopy in 41 patients revealed either no abnormalities or foveal retinal pigment epithelium (RPE) changes in 10 and 9 patients, respectively; the other 22 patients had foveal atrophy, atrophic RPE lesions, and/or irregular yellow-white fundus flecks. On FA, there was a "dark choroid" in 21 out of 29 patients. In 14 out of 50 patients, foveal atrophy occurred before flecks developed. On FAF, there was centrifugal expansion of disseminated atrophic spots, which progressed to the eventual profound chorioretinal atrophy. Spectral-domain OCT revealed early photoreceptor damage followed by atrophy of the outer retina, RPE, and choroid. On ffERG in 26 patients, 15 had normal amplitudes, and 11 had reduced photopic and/or scotopic amplitudes at their first visit. We found no correlation between ffERG abnormalities and the rate of vision loss. Thirteen out of 25 patients had progressive ffERG abnormalities. Finally, genetic screening of 44 patients revealed ≥2 ABCA4 mutations in 37 patients and single heterozygous mutations in 7. CONCLUSIONS In early-onset Stargardt, initial ophthalmoscopy can reveal no abnormalities or minor retinal abnormalities. Yellow-white flecks can be preceded by foveal atrophy and may be visible only on FAF. Although ffERG is insufficient for predicting the rate of vision loss, abnormalities can develop. Over time, visual acuity declines rapidly in parallel with progressive retinal degeneration, resulting in profound chorioretinal atrophy. Thus, early-onset Stargardt lies at the severe end of the spectrum of ABCA4-associated retinal phenotypes.
Collapse
Affiliation(s)
- Stanley Lambertus
- Department of Ophthalmology, Radboud university medical center, Nijmegen, The Netherlands
| | - Ramon A C van Huet
- Department of Ophthalmology, Radboud university medical center, Nijmegen, The Netherlands
| | - Nathalie M Bax
- Department of Ophthalmology, Radboud university medical center, Nijmegen, The Netherlands
| | - Lies H Hoefsloot
- Department of Human Genetics, Radboud university medical center, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud university medical center, Nijmegen, The Netherlands; Radboud Institute for Molecular Life Sciences, Radboud university medical center, Nijmegen, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Radboud university medical center, Nijmegen, The Netherlands; Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | - B Jeroen Klevering
- Department of Ophthalmology, Radboud university medical center, Nijmegen, The Netherlands
| | - Carel B Hoyng
- Department of Ophthalmology, Radboud university medical center, Nijmegen, The Netherlands.
| |
Collapse
|
21
|
Bertelsen M, Zernant J, Larsen M, Duno M, Allikmets R, Rosenberg T. Generalized choriocapillaris dystrophy, a distinct phenotype in the spectrum of ABCA4-associated retinopathies. Invest Ophthalmol Vis Sci 2014; 55:2766-76. [PMID: 24713488 DOI: 10.1167/iovs.13-13391] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE We describe a particular form of autosomal recessive generalized choriocapillaris dystrophy phenotype associated with ABCA4 mutations. METHODS A cohort of 30 patients with identified ABCA4 mutations and a distinct phenotype was studied. A retrospective review of history, fundus photographs, electroretinography, visual field testing, dark adaptometry, and optical coherence tomography was performed. Genetic analyses were performed by ABCA4 microarray analysis, high resolution melting, and/or next generation sequencing of all protein-coding sequences of the ABCA4 gene. RESULTS The earliest recorded manifestation of ABCA4-associated disease was a central bull's eye type of macular dystrophy that progressed to chorioretinal atrophy of the macula with coarse rounded hyperpigmentations and expanding involvement of the periphery. The mean age at first presentation was 10.3 years, the longest follow-up was 61 years. All patients had two ABCA4 mutations identified, confirming the molecular genetic diagnosis of an ABCA4-associated disease. Most patients harbored at least one mutation classified as "severe," the most common of which was the p.N965S variant that had been found previously at a high frequency among patients with ABCA4-associated retinal dystrophies in Denmark. CONCLUSIONS Generalized choriocapillaris dystrophy is a progressive ABCA4-associated phenotype characterized by early-onset macular dystrophy that disperses and expands to widespread end-stage chorioretinal atrophy with profound visual loss. All cases in this study were confirmed as harboring two ABCA4 mutations. Most of the ABCA4 mutations were classified as "severe" explaining the early onset, panretinal degeneration, and fast progression of the disease.
Collapse
Affiliation(s)
- Mette Bertelsen
- Department of Ophthalmology, Glostrup Hospital, Glostrup, Denmark
| | | | | | | | | | | |
Collapse
|
22
|
Cooper DN, Krawczak M, Polychronakos C, Tyler-Smith C, Kehrer-Sawatzki H. Where genotype is not predictive of phenotype: towards an understanding of the molecular basis of reduced penetrance in human inherited disease. Hum Genet 2013; 132:1077-130. [PMID: 23820649 PMCID: PMC3778950 DOI: 10.1007/s00439-013-1331-2] [Citation(s) in RCA: 407] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Accepted: 06/15/2013] [Indexed: 02/06/2023]
Abstract
Some individuals with a particular disease-causing mutation or genotype fail to express most if not all features of the disease in question, a phenomenon that is known as 'reduced (or incomplete) penetrance'. Reduced penetrance is not uncommon; indeed, there are many known examples of 'disease-causing mutations' that fail to cause disease in at least a proportion of the individuals who carry them. Reduced penetrance may therefore explain not only why genetic diseases are occasionally transmitted through unaffected parents, but also why healthy individuals can harbour quite large numbers of potentially disadvantageous variants in their genomes without suffering any obvious ill effects. Reduced penetrance can be a function of the specific mutation(s) involved or of allele dosage. It may also result from differential allelic expression, copy number variation or the modulating influence of additional genetic variants in cis or in trans. The penetrance of some pathogenic genotypes is known to be age- and/or sex-dependent. Variable penetrance may also reflect the action of unlinked modifier genes, epigenetic changes or environmental factors. At least in some cases, complete penetrance appears to require the presence of one or more genetic variants at other loci. In this review, we summarize the evidence for reduced penetrance being a widespread phenomenon in human genetics and explore some of the molecular mechanisms that may help to explain this enigmatic characteristic of human inherited disease.
Collapse
Affiliation(s)
- David N. Cooper
- Institute of Medical Genetics, School of Medicine, Cardiff University, Heath Park, Cardiff, CF14 4XN UK
| | - Michael Krawczak
- Institute of Medical Informatics and Statistics, Christian-Albrechts University, 24105 Kiel, Germany
| | | | - Chris Tyler-Smith
- The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA UK
| | | |
Collapse
|
23
|
Jonsson F, Burstedt MS, Sandgren O, Norberg A, Golovleva I. Novel mutations in CRB1 and ABCA4 genes cause Leber congenital amaurosis and Stargardt disease in a Swedish family. Eur J Hum Genet 2013; 21:1266-71. [PMID: 23443024 DOI: 10.1038/ejhg.2013.23] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 01/21/2013] [Accepted: 01/23/2013] [Indexed: 11/09/2022] Open
Abstract
This study aimed to identify genetic mechanisms underlying severe retinal degeneration in one large family from northern Sweden, members of which presented with early-onset autosomal recessive retinitis pigmentosa and juvenile macular dystrophy. The clinical records of affected family members were analysed retrospectively and ophthalmological and electrophysiological examinations were performed in selected cases. Mutation screening was initially performed with microarrays, interrogating known mutations in the genes associated with recessive retinitis pigmentosa, Leber congenital amaurosis and Stargardt disease. Searching for homozygous regions with putative causative disease genes was done by high-density SNP-array genotyping, followed by segregation analysis of the family members. Two distinct phenotypes of retinal dystrophy, Leber congenital amaurosis and Stargardt disease were present in the family. In the family, four patients with Leber congenital amaurosis were homozygous for a novel c.2557C>T (p.Q853X) mutation in the CRB1 gene, while of two cases with Stargardt disease, one was homozygous for c.5461-10T>C in the ABCA4 gene and another was carrier of the same mutation and a novel ABCA4 mutation c.4773+3A>G. Sequence analysis of the entire ABCA4 gene in patients with Stargardt disease revealed complex alleles with additional sequence variants, which were evaluated by bioinformatics tools. In conclusion, presence of different genetic mechanisms resulting in variable phenotype within the family is not rare and can challenge molecular geneticists, ophthalmologists and genetic counsellors.
Collapse
Affiliation(s)
- Frida Jonsson
- Department of Medical Biosciences/Medical and Clinical Genetics, University of Umeå, Umeå, Sweden
| | | | | | | | | |
Collapse
|
24
|
Chacón-Camacho OF, Granillo-Alvarez M, Ayala-Ramírez R, Zenteno JC. ABCA4 mutational spectrum in Mexican patients with Stargardt disease: Identification of 12 novel mutations and evidence of a founder effect for the common p.A1773V mutation. Exp Eye Res 2013; 109:77-82. [PMID: 23419329 DOI: 10.1016/j.exer.2013.02.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 01/16/2013] [Accepted: 02/04/2013] [Indexed: 01/10/2023]
Abstract
The aim of this study was to assess the mutational spectrum of the ABCA4 gene in a cohort of patients with Stargardt disease from Mexico, a previously uncharacterized population. Clinical diagnosis in each patient was supported by a complete ophthalmological assessment that included visual acuity measurement, a slit lamp examination, a fundus examination and photography, electroretinography, fluorescein angiography, and computerized visual fields testing. Molecular analysis was performed by PCR amplification and direct nucleotide sequence of the 50 exons of the ABCA4 gene in genomic DNA. A total of 31 unrelated subjects with the disease were enrolled in the study. Molecular analysis in the total group of 62 alleles allowed the identification of 46 mutant ABCA4 alleles carrying 29 different pathogenic disease-associated mutations. Two ABCA4 mutant alleles were detected in 20 of the 31 patients (64.5%), a single disease allele was identified in six (19.4%), and no mutant alleles were detected in five of the cases (16.1%). Most patients with two ABCA4 mutations (11/20, 55%) were compound heterozygotes. Twelve variants were novel ABCA4 mutations. Nucleotide substitutions were the most frequent type of variation, occurring in 26 out of 29 (89.7%) different mutations. The two most common mutations in our study were the missense changes p.A1773V and p.G818E, which were identified in eight (17%) and seven (15%) of the total 46 disease-associated alleles, respectively. Haplotype analyses of intragenic SNPs in four subjects carrying the p.A1773V mutation supported a common origin for this mutation. In conclusion, this is the first report of ABCA4 molecular screening in Latin American Stargardt disease patients. Our results expand the mutational spectrum of the disease by adding 12 novel ABCA4 pathogenic variants and support the occurrence of a founder effect for the p.A1773V mutation in the Mexican population. The identification of recurrent mutations in our cohort will direct future ABCA4 molecular screening in patients from this ethnic group.
Collapse
Affiliation(s)
- Oscar F Chacón-Camacho
- Department of Genetics-Research Unit, Institute of Ophthalmology Conde de Valenciana, Mexico City, Mexico
| | | | | | | |
Collapse
|
25
|
Westeneng-van Haaften SC, Boon CJF, Cremers FPM, Hoefsloot LH, den Hollander AI, Hoyng CB. Clinical and genetic characteristics of late-onset Stargardt's disease. Ophthalmology 2012; 119:1199-210. [PMID: 22449572 DOI: 10.1016/j.ophtha.2012.01.005] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 01/04/2012] [Accepted: 01/04/2012] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE To describe the genotype and phenotype of patients with a late-onset Stargardt's disease (STGD1). DESIGN Retrospective case series. PARTICIPANTS Twenty-one unrelated STGD1 patients with an age at onset of ≥45 years and ≥1 rare variant in the ABCA4 gene. METHODS Ophthalmologic examination, including best-corrected visual acuity (VA), Amsler grid testing, fundus photography, fluorescein angiography (FA), spectral-domain optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging, full-field electroretinography (ERG), multifocal ERG, and central visual field testing. Analysis of the ABCA4 gene was performed using microarray analysis, sequencing, and multiplex ligation-dependent probe amplification. In addition, the PRPH2 and CFH genes were sequenced. MAIN OUTCOME MEASURES Age at onset, VA, fundus appearance, FA, FAF, and OCT findings; ABCA4 mutations; and genotype-phenotype correlation. RESULTS The mean age at onset was 55 years (range, 45-72 years). Seven patients were diagnosed without visual symptoms (age range, 45-83 years). The VA was ≥20/40 in 24 eyes of 14 patients (59%) owing to foveal sparing. On ophthalmoscopy, late-onset STGD1 showed flavimaculatus flecks (15 patients), small flecks surrounding mottled foveal changes (3 patients), extensive chorioretinal atrophy (2 patients), or small yellowish spots in the macula (1 patient). The fundus flecks showed increased autofluorescence on FAF. The choroidal background fluorescence on FA was obscured in 16 patients (80%). We found a single heterozygous ABCA4 variant in 11 patients (52%), 2 compound heterozygous variants in 8 patients (38%), and a homozygous variant in 2 patients (10%). No PRPH2 or CFH mutations were detected. CONCLUSIONS Late-onset STGD1 is at the mild end of the spectrum of retinal dystrophies caused by ABCA4 mutations. The VA is frequently preserved in late-onset STGD1 patients owing to foveal sparing. This phenotype may be caused by 1 or 2 ABCA4 variants. The differential diagnosis between late-onset STGD1 and age-related macular degeneration may be challenging. A thorough clinical and genetic analysis makes a distinction possible, which is important for clinical and genetic counseling. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any of the materials discussed in this article.
Collapse
|
26
|
Espinós C, García-Cazorla A, Martínez-Rubio D, Martínez-Martínez E, Vilaseca MA, Pérez-Dueñas B, Kožich V, Palau F, Artuch R. Ancient origin of the CTH alelle carrying the c.200C>T (p.T67I) variant in patients with cystathioninuria. Clin Genet 2011; 78:554-9. [PMID: 20584029 DOI: 10.1111/j.1399-0004.2010.01431.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hereditary cystathioninuria is due to mutations in the CTH gene that encodes for cystathionase, a pyridoxal-5'-phosphate (PLP) dependent enzyme. To date, mutations in this gene have been described in 10 unrelated cystathioninuric patients. Enzyme assays have showed that mutated cystathionase exhibits lower activity than controls. As cystathioninuria is usually accompanied by a wide variety of symptoms, it has been questioned whether it is a disease or just a biochemical finding not associated with the clinical picture of these patients. This is the first report of Spanish patients with cystathioninuria and mild to severe neurological symptoms in childhood. After oral pyridoxine therapy biochemical parameters have normalized but clinical amelioration was not evident. All patients were homozygotes for the c.200C>T (p.T67I) variant which is the most prevalent inactivating mutation in the CTH gene. To further investigate the history of the alleles carrying the c.200C>T transition in Europe, we also constructed the haplotypes on the CTH locus in our Spanish patients as well as in a clinical series of cystathioninuric patients from the Czech Republic harboring the same nucleotide change. We suggest that the CTH p.T67I substitution could have an ancient common origin, which probably occurred in the Neolithic Era and spread throughout Europe.
Collapse
Affiliation(s)
- C Espinós
- CIBERER BIOBANK, CIBER de Enfermedades Raras (CIBERER), Valencia, Spain.
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Wright AF, Chakarova CF, Abd El-Aziz MM, Bhattacharya SS. Photoreceptor degeneration: genetic and mechanistic dissection of a complex trait. Nat Rev Genet 2010; 11:273-84. [PMID: 20212494 DOI: 10.1038/nrg2717] [Citation(s) in RCA: 434] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
|
28
|
Ducroq D, Shalev S, Habib A, Munnich A, Kaplan J, Rozet JM. Three different ABCA4 mutations in the same large family with several consanguineous loops affected with autosomal recessive cone–rod dystrophy. Eur J Hum Genet 2006; 14:1269-73. [PMID: 16896346 DOI: 10.1038/sj.ejhg.5201691] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A large multiplex family presumably affected with autosomal recessive cone-rod dystrophy (CRD) was ascertained from Israel. In this family of Christian Arab ancestry with six consanguineous loops, linkage analysis failed to identify homozygosity in all six nuclear families at any of the three arCORD loci hitherto reported. However, homozygosity was found at the CORD3 locus for two nuclear families and the segregation of three distinct haplotypes at this locus in the whole pedigree suggested the alteration of the ABCA4 gene. This hypothesis was confirmed by the identification of three distinct mutations. Subsequently, with regard to the wide spectrum of autosomal recessive retinal dystrophies related to ABCA4 mutations, the natural history of the disease was revisited in all patients. Although the diagnosis of CRD was confirmed in 8/9 patients, the last one, aged of 34, displayed typical signs of Stargardt disease without extension to the peripheral retina. The results of this study emphasize the pitfalls of homozygosity mapping in highly inbred families when the heterozygote carrier frequency is particularly high in the general population.
Collapse
Affiliation(s)
- Dominique Ducroq
- Unite de Recherches sur les Handicaps Génétiques de l'Enfants, Hôpital Necker-Enfants Malades, INSERM 393, 149 rue de Sèvres, 75743 Paris Cedex 15, France
| | | | | | | | | | | |
Collapse
|
29
|
Wiszniewski W, Zaremba CM, Yatsenko AN, Jamrich M, Wensel TG, Lewis RA, Lupski JR. ABCA4 mutations causing mislocalization are found frequently in patients with severe retinal dystrophies. Hum Mol Genet 2005; 14:2769-78. [PMID: 16103129 DOI: 10.1093/hmg/ddi310] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
ABCA4, also called ABCR, is a retinal-specific member of the ATP-binding cassette (ABC) family that functions in photoreceptor outer segments as a flipase of all-trans retinal. Homozygous and compound heterozygous ABCA4 mutations are associated with various autosomal recessive retinal dystrophies, whereas heterozygous ABCA4 mutations have been associated with dominant susceptibility to age-related macular degeneration in both humans and mice. We analyzed a cohort of 29 arRP families for the mutations in ABCA4 with a commercial microarray, ABCR-400 in addition to direct sequencing and segregation analysis, and identified both mutant alleles in two families (7%): compound heterozygosity for missense (R602W) and nonsense (R408X) alleles and homozygosity for a complex [L541P; A1038V] allele. The missense mutations were analyzed functionally in the photoreceptors of Xenopus laevis tadpoles, which revealed mislocalization of ABCA4 protein. These mutations cause retention of ABCA4 in the photoreceptor inner segment, likely by impairing correct folding, resulting in the total absence of physiologic protein function. Patients with different retinal dystrophies harboring two misfolding alleles exhibit early age-of-onset (AO) (5-12 years) of retinal disease. Our data suggest that a class of ABCA4 mutants may be an important determinant of the AO of disease.
Collapse
Affiliation(s)
- Wojciech Wiszniewski
- Department of Molecular and Human Genetics, Baylor college of Medicine, Houston, TX 77030, USA.
| | | | | | | | | | | | | |
Collapse
|
30
|
Abstract
Located between vessels of the choriocapillaris and light-sensitive outer segments of the photoreceptors, the retinal pigment epithelium (RPE) closely interacts with photoreceptors in the maintenance of visual function. Increasing knowledge of the multiple functions performed by the RPE improved the understanding of many diseases leading to blindness. This review summarizes the current knowledge of RPE functions and describes how failure of these functions causes loss of visual function. Mutations in genes that are expressed in the RPE can lead to photoreceptor degeneration. On the other hand, mutations in genes expressed in photoreceptors can lead to degenerations of the RPE. Thus both tissues can be regarded as a functional unit where both interacting partners depend on each other.
Collapse
Affiliation(s)
- Olaf Strauss
- Bereich Experimentelle Ophthalmologie, Klinik und Poliklinik fuer Augenheilkunde, Universitaetsklinikum Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
| |
Collapse
|
31
|
Kohl S, Varsanyi B, Antunes GA, Baumann B, Hoyng CB, Jägle H, Rosenberg T, Kellner U, Lorenz B, Salati R, Jurklies B, Farkas A, Andreasson S, Weleber RG, Jacobson SG, Rudolph G, Castellan C, Dollfus H, Legius E, Anastasi M, Bitoun P, Lev D, Sieving PA, Munier FL, Zrenner E, Sharpe LT, Cremers FPM, Wissinger B. CNGB3 mutations account for 50% of all cases with autosomal recessive achromatopsia. Eur J Hum Genet 2005; 13:302-8. [PMID: 15657609 DOI: 10.1038/sj.ejhg.5201269] [Citation(s) in RCA: 162] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Achromatopsia is a congenital, autosomal recessively inherited disorder characterized by a lack of color discrimination, low visual acuity (<0.2), photophobia, and nystagmus. Mutations in the genes for CNGA3, CNGB3, and GNAT2 have been associated with this disorder. Here, we analyzed the spectrum and prevalence of CNGB3 gene mutations in a cohort of 341 independent patients with achromatopsia. In 163 patients, CNGB3 mutations could be identified. A total of 105 achromats carried apparent homozygous mutations, 44 were compound (double) heterozygotes, and 14 patients had only a single mutant allele. The derived CNGB3 mutation spectrum comprises 28 different mutations including 12 nonsense mutations, eight insertions and/or deletions, five putative splice site mutations, and three missense mutations. Thus, the majority of mutations in the CNGB3 gene result in significantly altered and/or truncated polypeptides. Several mutations were found recurrently, in particular a 1 bp deletion, c.1148delC, which accounts for over 70% of all CNGB3 mutant alleles. In conclusion, mutations in the CNGB3 gene are responsible for approximately 50% of all patients with achromatopsia. This indicates that the CNGB3/ACHM3 locus on chromosome 8q21 is the major locus for achromatopsia in patients of European origin or descent.
Collapse
Affiliation(s)
- Susanne Kohl
- Molekulargenetisches Labor, Universitäts-Augenklinik Tübingen, Abt. Pathophysiologie des Sehens und Neuroophthalmologie, Germany.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Klevering BJ, Yzer S, Rohrschneider K, Zonneveld M, Allikmets R, van den Born LI, Maugeri A, Hoyng CB, Cremers FPM. Microarray-based mutation analysis of the ABCA4 (ABCR) gene in autosomal recessive cone-rod dystrophy and retinitis pigmentosa. Eur J Hum Genet 2005; 12:1024-32. [PMID: 15494742 DOI: 10.1038/sj.ejhg.5201258] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Mutations in the ABCA4 gene have been associated with autosomal recessive Stargardt disease (STGD1), cone-rod dystrophy (CRD), and retinitis pigmentosa (RP). We employed a recently developed genotyping microarray, the ABCR400-chip, to search for known ABCA4 mutations in patients with isolated or autosomal recessive CRD (54 cases) or RP (90 cases). We performed detailed ophthalmologic examinations and identified at least one ABCA4 mutation in 18 patients (33%) with CRD and in five patients (5.6%) with RP. Single-strand conformation polymorphism (SSCP) analysis and subsequent DNA sequencing revealed four novel missense mutations (R24C, E161K, P597S, G618E) and a novel 1-bp deletion (5888delG). Ophthalmoscopic abnormalities in CRD patients ranged from minor granular pigmentary changes in the posterior pole to widespread atrophy. In 12 patients with recordable electroretinogram (ERG) tracings, a cone-rod pattern was detected. Three patients demonstrated progression from a retinal dystrophy resembling STGD1 to a more widespread degeneration, and were subsequently diagnosed as CRD. In addition to a variable degree of atrophy, all RP patients displayed ophthalmologic characteristics of classic RP. When detectable, ERG recordings in these patients demonstrated rod-cone patterns of photoreceptor degeneration. In conclusion, in this study, we show that the ABCA4 mutation chip is an efficient first screening tool for arCRD.
Collapse
Affiliation(s)
- B Jeroen Klevering
- Department of Ophthalmology, University Medical Centre Nijmegen, Nijmegen, The Netherlands
| | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Jaakson K, Zernant J, Külm M, Hutchinson A, Tonisson N, Glavac D, Ravnik-Glavac M, Hawlina M, Meltzer MR, Caruso RC, Testa F, Maugeri A, Hoyng CB, Gouras P, Simonelli F, Lewis RA, Lupski JR, Cremers FPM, Allikmets R. Genotyping microarray (gene chip) for the ABCR (ABCA4) gene. Hum Mutat 2004; 22:395-403. [PMID: 14517951 DOI: 10.1002/humu.10263] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genetic variation in the ABCR (ABCA4) gene has been associated with five distinct retinal phenotypes, including Stargardt disease/fundus flavimaculatus (STGD/FFM), cone-rod dystrophy (CRD), and age-related macular degeneration (AMD). Comparative genetic analyses of ABCR variation and diagnostics have been complicated by substantial allelic heterogeneity and by differences in screening methods. To overcome these limitations, we designed a genotyping microarray (gene chip) for ABCR that includes all approximately 400 disease-associated and other variants currently described, enabling simultaneous detection of all known ABCR variants. The ABCR genotyping microarray (the ABCR400 chip) was constructed by the arrayed primer extension (APEX) technology. Each sequence change in ABCR was included on the chip by synthesis and application of sequence-specific oligonucleotides. We validated the chip by screening 136 confirmed STGD patients and 96 healthy controls, each of whom we had analyzed previously by single strand conformation polymorphism (SSCP) technology and/or heteroduplex analysis. The microarray was >98% effective in determining the existing genetic variation and was comparable to direct sequencing in that it yielded many sequence changes undetected by SSCP. In STGD patient cohorts, the efficiency of the array to detect disease-associated alleles was between 54% and 78%, depending on the ethnic composition and degree of clinical and molecular characterization of a cohort. In addition, chip analysis suggested a high carrier frequency (up to 1:10) of ABCR variants in the general population. The ABCR genotyping microarray is a robust, cost-effective, and comprehensive screening tool for variation in one gene in which mutations are responsible for a substantial fraction of retinal disease. The ABCR chip is a prototype for the next generation of screening and diagnostic tools in ophthalmic genetics, bridging clinical and scientific research.
Collapse
|