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Serrano-González J, Montes-Rodríguez I, Renta JY, Rojas R, Cadilla CL. After an initial Hermansky-Pudlak syndrome clinical diagnosis, molecular testing reveals variants for oculocutaneous albinism type 1B: A case report. Mol Genet Genomic Med 2024; 12:e2493. [PMID: 38994739 PMCID: PMC11240142 DOI: 10.1002/mgg3.2493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 06/19/2024] [Accepted: 07/02/2024] [Indexed: 07/13/2024] Open
Abstract
BACKGROUND Albinism is a heterogeneous condition in which patients present complete absence, reduction, or normal pigmentation in skin, hair and eyes in addition to ocular defects. One of the heterogeneous forms of albinism is observed in Hermansky-Pudlak syndrome (HPS) patients. HPS is characterized by albinism and hemorrhagic diathesis due to the absence of dense bodies in platelets. METHODS In this report, we describe a case of a pair of Puerto Rican siblings with albinism that were clinically diagnosed with HPS during childhood. Since they did not harbor the founder changes in the HPS1 and HPS3 genes common in Puerto Ricans, as adults they wanted to know the type of albinism they had. We performed exome sequencing, validation by PCR, and cloning of PCR products followed by Sanger sequencing in the family members. RESULTS We discovered no mutations that could explain an HPS diagnosis. Instead, we found the siblings were compound heterozygotes for 4 variants in the Tyrosinase gene: c.-301C>T, c.140G>A (rs61753180; p.G47D), c.575C>A (rs1042602; p.S192Y), and c.1205G>A (rs1126809; p.R402Q). Our results show that the correct diagnosis for the siblings is OCA1B. CONCLUSION Our study shows the importance of molecular testing when diagnosing a rare genetic disorder, especially in populations were the disease prevalence is higher.
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Affiliation(s)
- Joseline Serrano-González
- Deptartment of Biochemistry, Medical Sciences Campus, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico
| | | | - Jessicca Y Renta
- Deptartment of Biochemistry, Medical Sciences Campus, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico
| | - Ricardo Rojas
- Deptartment of Biochemistry, Medical Sciences Campus, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico
| | - Carmen L Cadilla
- Deptartment of Biochemistry, Medical Sciences Campus, School of Medicine, University of Puerto Rico, San Juan, Puerto Rico
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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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Chan HW, Schiff ER, Tailor VK, Malka S, Neveu MM, Theodorou M, Moosajee M. Prospective Study of the Phenotypic and Mutational Spectrum of Ocular Albinism and Oculocutaneous Albinism. Genes (Basel) 2021; 12:508. [PMID: 33808351 PMCID: PMC8065601 DOI: 10.3390/genes12040508] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/15/2021] [Accepted: 03/26/2021] [Indexed: 02/07/2023] Open
Abstract
Albinism encompasses a group of hereditary disorders characterized by reduced or absent ocular pigment and variable skin and/or hair involvement, with syndromic forms such as Hermansky-Pudlak syndrome and Chédiak-Higashi syndrome. Autosomal recessive oculocutaneous albinism (OCA) is phenotypically and genetically heterogenous (associated with seven genes). X-linked ocular albinism (OA) is associated with only one gene, GPR143. We report the clinical and genetic outcomes of 44 patients, from 40 unrelated families of diverse ethnicities, with query albinism presenting to the ocular genetics service at Moorfields Eye Hospital NHS Foundation Trust between November 2017 and October 2019. Thirty-six were children (≤ 16 years) with a median age of 31 months (range 2-186), and eight adults with a median age of 33 years (range 17-39); 52.3% (n = 23) were male. Genetic testing using whole genome sequencing (WGS, n = 9) or a targeted gene panel (n = 31) gave an overall diagnostic rate of 42.5% (44.4% (4/9) with WGS and 41.9% (13/31) with panel testing). Seventeen families had confirmed mutations in TYR (n = 9), OCA2, (n = 4), HPS1 (n = 1), HPS3 (n = 1), HPS6 (n = 1), and GPR143 (n = 1). Molecular diagnosis of albinism remains challenging due to factors such as missing heritability. Differential diagnoses must include SLC38A8-associated foveal hypoplasia and syndromic forms of albinism.
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Affiliation(s)
- Hwei Wuen Chan
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Department of Ophthalmology, National University Singapore, Singapore S118177, Singapore
| | - Elena R. Schiff
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Vijay K. Tailor
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
- Experimental Psychology, University College London, London WC1H 0AP, UK
| | - Samantha Malka
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
| | - Magella M. Neveu
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Maria Theodorou
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
| | - Mariya Moosajee
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, UK; (H.W.C.); (E.R.S.); (V.K.T.); (S.M.); (M.M.N.); (M.T.)
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
- The Francis Crick Institute, London NW1 1AT, UK
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Mendez R, Iqbal S, Vishnopolska S, Martinez C, Dibner G, Aliano R, Zaiat J, Biagioli G, Fernandez C, Turjanski A, Campbell AJ, Mercado G, Marti MA. Oculocutaneous albinism type 1B associated with a functionally significant tyrosinase gene polymorphism detected with Whole Exome Sequencing. Ophthalmic Genet 2021; 42:291-295. [PMID: 33599182 DOI: 10.1080/13816810.2021.1888129] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Background: Oculocutaneous albinism (OCA) is a Mendelian disorder characterized by hypopigmentation of the skin, hair, and eyes, hypoplastic fovea, and low vision, known to be caused by mutations in the Tyrosinase (TYR) gene. Among the known TYR variants, some reduce but do not completely eliminate tyrosinase activity, allowing residual production of melanin and resulting in a contradictory assignment as either pathogenic or benign, preventing a precise clinical diagnostic.Materials and Methods: In the present work, we performed Whole Exome Sequencing and subsequent Sanger sequencing in a young male clinically diagnosed with OCA.Results: Whole-exome sequencing analysis revealed the identification of two variants in trans in TYR. The first, corresponds to a known pathogenic variant G47D, while the second S192Y, was considered a polymorphism due to its relatively high frequency in the European population.Conclusion: The lack of other pathogenic variants in TYR, the reported reduced enzymatic activity (ca. 40% respect to wt) for S192Y, together with the structural in-silico analysis strongly suggest that both reported variants are jointly disease-causing and that S192Y should be considered as likely pathogenic, especially when it is found in trans with a null variant.
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Affiliation(s)
- Rodrigo Mendez
- Centro Nacional de Genética Médica "Dr. Eduardo E. Castilla", ANLIS, Buenos Aires, Argentina
| | - Sumaiya Iqbal
- Center for Development of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA.,Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA.,Analytic and Translational Genetics Unit, Massachusetts General Hospital, Boston, Massachusetts, USA
| | | | - Cinthia Martinez
- Centro Nacional de Genética Médica "Dr. Eduardo E. Castilla", ANLIS, Buenos Aires, Argentina
| | - Glenda Dibner
- Departamento de Oftalmología, Hospital Rivadavia, Buenos Aires, Argentina
| | - Rocio Aliano
- Departamento de Oftalmología, Hospital Rivadavia, Buenos Aires, Argentina
| | - Jonathan Zaiat
- Departamento de Química Biológica, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Ciudad Universitaria, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Germán Biagioli
- Universidad de Buenos Aires, Buenos Aires, Argentina.,Departamento de Bioinformática, Bitgenia, Buenos Aires, Argentina
| | | | - Adrian Turjanski
- Departamento de Química Biológica, Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales (IQUIBICEN) CONICET, Ciudad Universitaria, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Arthur J Campbell
- Center for Development of Therapeutics, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA.,Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts, USA
| | - Graciela Mercado
- Centro Nacional de Genética Médica "Dr. Eduardo E. Castilla", ANLIS, Buenos Aires, Argentina
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Wang NK, Chiang JPW. Increasing evidence of combinatory variant effects calls for revised classification of low-penetrance alleles. Genet Med 2018; 21:1280-1282. [PMID: 30385887 PMCID: PMC6752265 DOI: 10.1038/s41436-018-0347-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 10/15/2018] [Indexed: 11/09/2022] Open
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Comprehensive Review of the Genetics of Albinism. JOURNAL OF VISUAL IMPAIRMENT & BLINDNESS 2018. [DOI: 10.1177/0145482x1811200604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Introduction It is important to understand albinism, since it is a disorder associated with visual impairment, predisposition to malignant melanomas, and social stigma. The main objective of this article is to review the genetics and biologic mechanisms of the non-syndromic albinism subtypes and to describe associated clinical manifestations. We also discuss research on its treatments. Methods A review of the published literature on albinism subtypes was performed, spanning basic laboratory research, published case reports, and experiences of people with albinism. Results Clear progress has been made in comprehending the causes of albinism; research has shed light on the complexity of the disorder and has led to the molecular classification of subtypes. Discussion Despite the increase in knowledge with regards to albinism, gaps still exist. It is important to continue the pursuit of unraveling the mechanism of the disorder and to monitor the frequency of the subtypes worldwide in order to aid in the development of treatments. Furthermore, disseminating knowledge of albinism is crucial for future progress. Implications for practitioners Albinism is a disorder characterized by hypopigmentation of the hair, skin, and eyes, with accompanying ocular abnormalities that remain relatively stable throughout life. The disorder is defined by a spectrum of pigmentation where albinism is more evident among individuals of dark complexion than their lighter-pigmented peers. Patients with albinism require protection against sun exposure and special resources to address visual impairments. When albinism patients are diagnosed and properly accommodated, they generally report a positive quality of life.
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Ghodsinejad Kalahroudi V, Kamalidehghan B, Arasteh Kani A, Aryani O, Tondar M, Ahmadipour F, Chung LY, Houshmand M. Two novel tyrosinase (TYR) gene mutations with pathogenic impact on oculocutaneous albinism type 1 (OCA1). PLoS One 2014; 9:e106656. [PMID: 25216246 PMCID: PMC4162572 DOI: 10.1371/journal.pone.0106656] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Accepted: 08/06/2014] [Indexed: 11/19/2022] Open
Abstract
Oculocutaneous albinism (OCA) is a heterogeneous group of autosomal recessive disorders resulting from mutations of the tyrosinase (TYR) gene and presents with either complete or partial absence of pigment in the skin, hair and eyes due to a defect in an enzyme involved in the production of melanin. In this study, mutations in the TYR gene of 30 unrelated Iranian OCA1 patients and 100 healthy individuals were examined using PCR-sequencing. Additionally, in order to predict the possible effects of new mutations on the structure and function of tyrosinase, these mutations were analyzed by SIFT, PolyPhen and I-Mutant 2 software. Here, two new pathogenic p.C89S and p.H180R mutations were detected in two OCA1 patients. Moreover, the R402Q and S192Y variants, which are common non-pathogenic polymorphisms, were detected in 17.5% and 35% of the patients, respectively. The outcome of this study has extended the genotypic spectrum of OCA1 patients, which paves the way for more efficient carrier detection and genetic counseling.
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Affiliation(s)
- Vadieh Ghodsinejad Kalahroudi
- Department of Biology, Kharazmi University, Tehran, Iran
- Department of Medical Genetics, Special Medical Center, Tehran, Iran
| | - Behnam Kamalidehghan
- Department of Pharmacy, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | | | - Omid Aryani
- Department of Medical Genetics, Special Medical Center, Tehran, Iran
| | - Mahdi Tondar
- Department of Medical Genetics, Special Medical Center, Tehran, Iran
- Department of Biochemistry and Molecular & Cellular Biology, Georgetown University, Washington, D.C., United States of America
| | - Fatemeh Ahmadipour
- Department of Pharmacy, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Lip Yong Chung
- Department of Pharmacy, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Massoud Houshmand
- Department of Medical Genetics, Special Medical Center, Tehran, Iran
- Department of Medical Genetics, National Institute for Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran
- * E-mail:
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Jagirdar K, Smit DJ, Ainger SA, Lee KJ, Brown DL, Chapman B, Zhen Zhao Z, Montgomery GW, Martin NG, Stow JL, Duffy DL, Sturm RA. Molecular analysis of common polymorphisms within the human Tyrosinase locus and genetic association with pigmentation traits. Pigment Cell Melanoma Res 2014; 27:552-64. [PMID: 24739399 DOI: 10.1111/pcmr.12253] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 04/14/2014] [Indexed: 01/13/2023]
Abstract
We have compared the melanogenic activities of cultured melanocytes carrying two common TYR alleles as homozygous 192S-402R wild-type, heterozygous and homozygous variant. This includes assays of TYR protein, DOPAoxidase activity, glycosylation and temperature sensitivity of protein and DOPAoxidase levels. Homozygous wild-type strains on average had higher levels of TYR protein and enzyme activity than other genotypes. Homozygous 402Q/Q melanocytes produced significantly less TYR protein, displayed altered trafficking and glycosylation, with reduced DOPAoxidase. However, near wild-type TYR activity levels could be recovered at lower growth temperature. In a sample population from Southeast Queensland, these two polymorphisms were present on four TYR haplotypes, designated as WT 192S-402R, 192Y-402R and 192S-402Q with a double-variant 192Y-402Q of low frequency at 1.9%. Based on cell culture findings and haplotype associations, we have used an additive model to assess the penetrance of the ten possible TYR genotypes derived from the combination of these haplotypes.
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Affiliation(s)
- Kasturee Jagirdar
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Qld, Australia
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Rooryck C, Morice F, Lacombe D, Taieb A, Arveiler B. Genetic basis of oculocutaneous albinism. ACTA ACUST UNITED AC 2014. [DOI: 10.1586/edm.09.53] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Vidal-Ríos P, Fernández-Seara M, Cortés E, Hurtado L, Couce M. Albinismo oculocutáneo 1B asociado a una nueva mutación en el gen TYR. An Pediatr (Barc) 2013; 78:339-40. [DOI: 10.1016/j.anpedi.2012.09.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 07/22/2012] [Accepted: 09/05/2012] [Indexed: 10/27/2022] Open
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Simeonov DR, Wang X, Wang C, Sergeev Y, Dolinska M, Bower M, Fischer R, Winer D, Dubrovsky G, Balog JZ, Huizing M, Hart R, Zein WM, Gahl WA, Brooks BP, Adams DR. DNA variations in oculocutaneous albinism: an updated mutation list and current outstanding issues in molecular diagnostics. Hum Mutat 2013; 34:827-35. [PMID: 23504663 DOI: 10.1002/humu.22315] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 03/08/2013] [Indexed: 12/20/2022]
Abstract
Oculocutaneous albinism (OCA) is a rare genetic disorder of melanin synthesis that results in hypopigmented hair, skin, and eyes. There are four types of OCA caused by mutations in TYR (OCA-1), OCA2 (OCA-2), TYRP1 (OCA-3), or SLC45A2 (OCA-4). Here we report 22 novel mutations in the OCA genes; 14 from a cohort of 61 patients seen as part of the NIH OCA Natural History Study and eight from a prior study at the University of Minnesota. We also include a comprehensive list of almost 600 previously reported OCA mutations along with ethnicity information, carrier frequencies, and in silico pathogenicity predictions as a supplement. In addition to discussing the clinical and molecular features of OCA, we address the cases of apparent missing heritability. In our cohort, 26% of patients did not have two mutations in a single OCA gene. We demonstrate the utility of multiple detection methods to reveal mutations missed by Sanger sequencing. Finally, we review the TYR p.R402Q temperature-sensitive variant and confirm its association with cases of albinism with only one identifiable TYR mutation.
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Affiliation(s)
- Dimitre R Simeonov
- National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
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Chiang PW, Spector E, McGregor TL. Evidence suggesting digenic inheritance of Waardenburg syndrome type II with ocular albinism. Am J Med Genet A 2009; 149A:2739-44. [DOI: 10.1002/ajmg.a.33128] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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