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Lin S, Sanchez-Bretaño A, Leslie JS, Williams KB, Lee H, Thomas NS, Callaway J, Deline J, Ratnayaka JA, Baralle D, Schmitt MA, Norman CS, Hammond S, Harlalka GV, Ennis S, Cross HE, Wenger O, Crosby AH, Baple EL, Self JE. Evidence that the Ser192Tyr/Arg402Gln in cis Tyrosinase gene haplotype is a disease-causing allele in oculocutaneous albinism type 1B (OCA1B). NPJ Genom Med 2022; 7:2. [PMID: 35027574 PMCID: PMC8758782 DOI: 10.1038/s41525-021-00275-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/19/2021] [Indexed: 01/09/2023] Open
Abstract
Oculocutaneous albinism type 1 (OCA1) is caused by pathogenic variants in the TYR (tyrosinase) gene which encodes the critical and rate-limiting enzyme in melanin synthesis. It is the most common OCA subtype found in Caucasians, accounting for ~50% of cases worldwide. The apparent 'missing heritability' in OCA is well described, with ~25-30% of clinically diagnosed individuals lacking two clearly pathogenic variants. Here we undertook empowered genetic studies in an extensive multigenerational Amish family, alongside a review of previously published literature, a retrospective analysis of in-house datasets, and tyrosinase activity studies. Together this provides irrefutable evidence of the pathogenicity of two common TYR variants, p.(Ser192Tyr) and p.(Arg402Gln) when inherited in cis alongside a pathogenic TYR variant in trans. We also show that homozygosity for the p.(Ser192Tyr)/p.(Arg402Gln) TYR haplotype results in a very mild, but fully penetrant, albinism phenotype. Together these data underscore the importance of including the TYR p.(Ser192Tyr)/p.(Arg402Gln) in cis haplotype as a pathogenic allele causative of OCA, which would likely increase molecular diagnoses in this missing heritability albinism cohort by 25-50%.
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Affiliation(s)
- Siying Lin
- RILD Wellcome Wolfson Centre, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, UK
| | - Aida Sanchez-Bretaño
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Joseph S Leslie
- RILD Wellcome Wolfson Centre, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, UK
| | - Katie B Williams
- Center for Special Children, Vernon Memorial Healthcare, La Farge, WI, USA
| | - Helena Lee
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- Southampton Eye Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - N Simon Thomas
- Faculty of Medicine, University of Southampton, Southampton, UK
- Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, UK
| | - Jonathan Callaway
- Faculty of Medicine, University of Southampton, Southampton, UK
- Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, UK
| | - James Deline
- Center for Special Children, Vernon Memorial Healthcare, La Farge, WI, USA
| | - J Arjuna Ratnayaka
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Diana Baralle
- Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, UK
| | - Melanie A Schmitt
- University of Wisconsin School of Medicine and Public Health, Department of Ophthalmology & Visual Sciences, Madison, WI, USA
| | - Chelsea S Norman
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK
- The Rosalind Franklin Institute, Rutherford Appleton Laboratories, Harwell Science and Innovation Campus, Didcot, UK
| | - Sheri Hammond
- Center for Special Children, Vernon Memorial Healthcare, La Farge, WI, USA
| | - Gaurav V Harlalka
- RILD Wellcome Wolfson Centre, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, UK
- Rajarshi Shahu College of Pharmacy, Malvihir, Buldana, India
| | - Sarah Ennis
- Department of Human Genetics and Genomic Medicine, University of Southampton, Southampton, UK
| | - Harold E Cross
- Department of Ophthalmology, University of Arizona College of Medicine, Tucson, AZ, USA
| | - Olivia Wenger
- New Leaf Clinic, PO Box 336, 16014 East Chestnut Street, Mount Eaton, OH, 44691, USA
- Department of Pediatrics, Akron Children's Hospital, 214 West Bowery Street, Akron, OH, 44308, USA
| | - Andrew H Crosby
- RILD Wellcome Wolfson Centre, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, UK.
| | - Emma L Baple
- RILD Wellcome Wolfson Centre, Royal Devon & Exeter NHS Foundation Trust, Barrack Road, Exeter, UK.
- Peninsula Clinical Genetics Service, Royal Devon & Exeter Hospital (Heavitree), Gladstone Road, Exeter, UK.
| | - Jay E Self
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, UK.
- Southampton Eye Unit, University Hospital Southampton NHS Foundation Trust, Southampton, UK.
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A pathogenic haplotype, common in Europeans, causes autosomal recessive albinism and uncovers missing heritability in OCA1. Sci Rep 2019; 9:645. [PMID: 30679655 PMCID: PMC6345944 DOI: 10.1038/s41598-018-37272-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 11/28/2018] [Indexed: 11/08/2022] Open
Abstract
Oculocutaneous albinism (OCA) is a genetically heterogeneous disorder. Six genes are associated with autosomal recessive OCA (TYR, OCA2, TYRP1, SLC45A2, SLC24A5 and LRMDA), and one gene, GPR143, is associated with X-linked ocular albinism (OA). Molecular genetic analysis provides a genetic diagnosis in approximately 60% of individuals with clinical OA/OCA. A considerably number of the remaining 40% are heterozygous for a causative sequence variation in TYR. To identify missing causative sequence variants in these, we used a NGS based approach, genotyping and segregation analysis. We report two putative pathogenic haplotypes which only differ by two extremely rare SNVs, indicating that the haplotypes have a common derivation. Both haplotypes segregate consistent with an autosomal recessive inheritance pattern and include the allele p.S192Y-p.R402Q. An explanation for the pathogenicity of the haplotypes could be the combination of p.S192Y and p.R402Q. Homozygosity for the pathogenic haplotypes causes a partial albinism phenotype. In our cohort, 15% of affected individuals had a molecular genetic diagnosis involving the pathogenic haplotype. Consequently, the prevalence of albinism seems to be substantially underestimated, and children with unexplained bilateral subnormal vision and/or nystagmus should be analysed clinically and molecularly for albinism.
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Poulter J, Al-Araimi M, Conte I, van Genderen M, Sheridan E, Carr I, Parry D, Shires M, Carrella S, Bradbury J, Khan K, Lakeman P, Sergouniotis P, Webster A, Moore A, Pal B, Mohamed M, Venkataramana A, Ramprasad V, Shetty R, Saktivel M, Kumaramanickavel G, Tan A, Mackey D, Hewitt A, Banfi S, Ali M, Inglehearn C, Toomes C. Recessive mutations in SLC38A8 cause foveal hypoplasia and optic nerve misrouting without albinism. Am J Hum Genet 2013; 93:1143-50. [PMID: 24290379 PMCID: PMC3853409 DOI: 10.1016/j.ajhg.2013.11.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/05/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022] Open
Abstract
Foveal hypoplasia and optic nerve misrouting are developmental defects of the visual pathway and only co-occur in connection with albinism; to date, they have only been associated with defects in the melanin-biosynthesis pathway. Here, we report that these defects can occur independently of albinism in people with recessive mutations in the putative glutamine transporter gene SLC38A8. Nine different mutations were identified in seven Asian and European families. Using morpholino-mediated ablation of Slc38a8 in medaka fish, we confirmed that pigmentation is unaffected by loss of SLC38A8. Furthermore, by undertaking an association study with SNPs at the SLC38A8 locus, we showed that common variants within this gene modestly affect foveal thickness in the general population. This study reveals a melanin-independent component underpinning the development of the visual pathway that requires a functional role for SLC38A8.
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Affiliation(s)
- James A. Poulter
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Musallam Al-Araimi
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Ivan Conte
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
| | | | - Eamonn Sheridan
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
- Department of Clinical Genetics, St. James’s University Hospital, Leeds, West Yorkshire LS9 7TF, UK
| | - Ian M. Carr
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - David A. Parry
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Mike Shires
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Sabrina Carrella
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
| | - John Bradbury
- Department of Ophthalmology, Bradford Royal Infirmary, Bradford, West Yorkshire BD9 6RJ, UK
| | - Kamron Khan
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Phillis Lakeman
- Department of Clinical Genetics, VU University Medical Center, Amsterdam NL-1081 HV, the Netherlands
| | - Panagiotis I. Sergouniotis
- Division of Inherited Eye Disease, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | - Andrew R. Webster
- Division of Inherited Eye Disease, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | - Anthony T. Moore
- Division of Inherited Eye Disease, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | | | - Moin D. Mohamed
- Department of Ophthalmology, St. Thomas’ Hospital, London SE1 9RT, UK
| | | | | | - Rohit Shetty
- Department of Ocular Genetics, Narayana Nethralaya, Bangalore, Karnataka 560099, India
| | | | | | - Alex Tan
- Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, Perth WA 6009, Australia
| | - David A. Mackey
- Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, Perth WA 6009, Australia
| | - Alex W. Hewitt
- Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, Perth WA 6009, Australia
| | - Sandro Banfi
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
- Medical Genetics, Department of Biochemistry, Biophysics, and General Pathology, Second University of Naples, Naples 80138, Italy
| | - Manir Ali
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Chris F. Inglehearn
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Carmel Toomes
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
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Abstract
PURPOSE OF REVIEW To describe the entity of Lyonization in ocular eye diseases, along with its clinical and counseling implications. RECENT FINDINGS Several X-linked ocular diseases such as choroideremia, X-linked retinitis pigmentosa, and X-linked ocular albinism may have signs of Lyonization on ocular examination and diagnostic testing. These findings may aid in the proper diagnosis of ocular disease in both female carriers and their affected male relatives. SUMMARY Manifestations of Lyonization in the eye may help in the diagnosis of X-linked ocular diseases which may lead to accurate diagnosis, appropriate molecular genetic testing and genetic counseling.
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Halfeld Furtado de Mendonça R, Abbruzzese S, Bagolini B, Nofroni I, Ferreira EL, Odom JV. Visual evoked potential importance in the complex mechanism of amblyopia. Int Ophthalmol 2013; 33:515-9. [PMID: 23417145 PMCID: PMC3782652 DOI: 10.1007/s10792-013-9734-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2012] [Accepted: 01/29/2013] [Indexed: 11/10/2022]
Abstract
To compare the visual evoked potential (VEP) responses of amblyopic eyes with VEP responses of sound eyes in amblyopic children. A study of 65 amblyopic children with pattern-reversal VEPs elicited by checkerboard stimuli with large, medium and small checks. The children were classified into three groups: Group A, 22 children with anisometropic amblyopia; Group B, 16 children with exotropic strabismic amblyopia; and Group C, 27 children with esotropic strabismic amblyopia. Visual acuity (VA) was significantly worse in the amblyopic eye as compared to the sound eye. However, no statistically significant difference was found between the amblyopic and sound eye of amblyopic children in the three groups for VEP P1 amplitude and latencies for any check sizes. VEP is a very important tool in understanding the complex amblyopic mechanism. Although the sound eye has superior VA, the absence of differences in VEP P1 amplitudes and latencies demonstrate the functional abnormality of the eye considered ‘good’. More studies are necessary to explain why the sound eye in amblyopic children cannot be considered completely normal. Special attention should therefore be paid to amblyopic treatment, as patching can have a negative effect on the sound eye.
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Ekström AB, Tulinius M, Sjöström A, Aring E. Visual function in congenital and childhood myotonic dystrophy type 1. Ophthalmology 2010; 117:976-82. [PMID: 20346513 DOI: 10.1016/j.ophtha.2010.01.055] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Revised: 01/28/2010] [Accepted: 01/28/2010] [Indexed: 01/19/2023] Open
Abstract
OBJECTIVE To investigate visual function in a group of individuals with congenital and childhood myotonic dystrophy type 1 (DM1), to correlate the results to the size of the cytosine-thymine-guanine (CTG) repeat expansion and the onset form, and to compare the results with those of a control group. DESIGN Cross-sectional study with age- and gender-matched control groups. PARTICIPANTS AND CONTROLS Forty-nine individuals with severe and mild congenital and childhood DM1 and controls matched for age and gender. METHODS The ophthalmologic examination included best-corrected visual acuity (BCVA), refraction, slit-lamp biomicroscopy, indirect ophthalmoscopy, and flash visual evoked potentials (VEPs). MAIN OUTCOME MEASURES Visual acuity, refractive error, pathology of lens, fundus, and VEP pathologic features. RESULTS The study shows a higher prevalence of low visual acuity, hyperopia, and astigmatism in the study population compared with the controls. The size of the CTG repeat expansion had an impact on BCVA in all subgroups with lower values in individuals with larger expansion size. In childhood DM1, individuals with high hyperopia and astigmatism had greater CTG repeat expansion size than those without. No true cataract was found. Subtle nonspecific fundus changes were present in addition to VEP pathology. CONCLUSIONS Children and adolescents with DM1 have a variety of visual function pathologies, and DM1 has an impact on the developing visual system, necessitating early ophthalmologic assessment and follow-up.
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Affiliation(s)
- Anne-Berit Ekström
- Department of Pediatrics, Northern Alvsborg County Hospital, Trollhättan, Sweden.
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Abstract
Recent years have shown an impressive rise in high quality research on amblyopia. Unfortunately, the condition is not sufficiently defined, and consequently different studies have been used different definitions of amblyopia. Aspects in need of consideration include the degree of visual acuity reduction, magnitude of interocular difference in acuity, method of visual acuity testing used, the effect of refractive adaption, the presence of amblyogenic factors, the absence of organic cause and the treat ability of the deficit. Vision scientists worldwide are encouraged to jointly decide on what is, and what is not, amblyopia.
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Affiliation(s)
- Josefin Ohlsson
- Department of Clinical Neurophysiology, Göteborg University, Sahlgrenska University Hospital, Sweden.
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