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Owete AC, Ionin R, Huryn LA, Cukras CA, Blain D, Agather AR, Hufnagel RB, Brooks BP, Nwanyanwu K, Zein WM. Seeing in Color: Inclusion and Characterization of Hereditary Eye Disease in African Americans. Transl Vis Sci Technol 2024; 13:4. [PMID: 39226063 DOI: 10.1167/tvst.13.9.4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024] Open
Abstract
Purpose Hereditary eye diseases (HEDs) are individually rare but affect millions globally. The era of molecular genetics has ushered major advances in the study of these disorders; however, the inclusivity and population diversity of this research is unknown. Questions on the accuracy and applicability of these findings in diverse populations, especially African American patients, came up consistently during counselling sessions. This also raised the possibility of missed opportunities for broader understanding of these rare diseases. We conducted a literature review to measure the representation of African Americans in genomic research surrounding nine HEDs. Methods A detailed literature search using a predetermined set of search terms for each of nine HED categories was performed across PubMed, Embase, Web of Science, and Scopus focusing on studies published between Jan 1990 and July 2021. Predetermined inclusion criteria were applied to filter the sources. Results We identified 46 studies clearly reporting HED characterization in African Americans. Analysis of these inclusive studies revealed unique findings demonstrating the known usefulness of including diverse cohorts in genomics research. Conclusions HED characterization in diverse participants, specifically African Americans, is identified as a knowledge gap area. Genomic research is more applicable to patients when conducted in populations that share their ancestral background. Greater inclusion of African Americans in ophthalmic genetics research is a scientific imperative and a needed step in the pursuit of the best possible patient care for populations of all ancestries. Translational Relevance This work reveals gaps in genomic research in African Americans with HEDs.
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Affiliation(s)
- Agnes C Owete
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Raisa Ionin
- National Institutes of Health Library, National Institutes of Health, Bethesda, MD, USA
| | - Laryssa A Huryn
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Catherine A Cukras
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Delphine Blain
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Aime R Agather
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Robert B Hufnagel
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Brian P Brooks
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
| | - Kristen Nwanyanwu
- Department of Ophthalmology and Visual Science, Yale School of Medicine, New Haven, CT, USA
| | - Wadih M Zein
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institute of Health, Bethesda, MD, USA
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Diallo M, Courdier C, Mercier E, Sequeira A, Defay-Stinat A, Plaisant C, Mesdaghi S, Rigden D, Javerzat S, Lasseaux E, Bourgeade L, Audebert-Bellanger S, Dollfus H, Hadj-Rabia S, Morice-Picard F, Philibert M, Sidibé MK, Smirnov V, Sylla O, Michaud V, Arveiler B. Functional Characterization of Splice Variants in the Diagnosis of Albinism. Int J Mol Sci 2024; 25:8657. [PMID: 39201349 PMCID: PMC11355033 DOI: 10.3390/ijms25168657] [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: 07/02/2024] [Revised: 07/26/2024] [Accepted: 08/03/2024] [Indexed: 09/02/2024] Open
Abstract
Albinism is a genetically heterogeneous disease in which 21 genes are known so far. Its inheritance mode is autosomal recessive except for one X-linked form. The molecular analysis of exonic sequences of these genes allows for about a 70% diagnostic rate. About half (15%) of the unsolved cases are heterozygous for one pathogenic or probably pathogenic variant. Assuming that the missing variant may be located in non-coding regions, we performed sequencing for 122 such heterozygous patients of either the whole genome (27 patients) or our NGS panel (95 patients) that includes, in addition to all exons of the 21 genes, the introns and flanking sequences of five genes, TYR, OCA2, SLC45A2, GPR143 and HPS1. Rare variants (MAF < 0.01) in trans to the first variant were tested by RT-PCR and/or minigene assay. Of the 14 variants tested, nine caused either exon skipping or the inclusion of a pseudoexon, allowing for the diagnosis of 11 patients. This represents 9.8% (12/122) supplementary diagnosis for formerly unsolved patients and 75% (12/16) of those in whom the candidate variant was in trans to the first variant. Of note, one missense variant was demonstrated to cause skipping of the exon in which it is located, thus shedding new light on its pathogenic mechanism. Searching for non-coding variants and testing them for an effect on RNA splicing is warranted in order to increase the diagnostic rate.
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Affiliation(s)
- Modibo Diallo
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
| | - Cécile Courdier
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France; (C.P.); (E.L.); (L.B.)
| | - Elina Mercier
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
| | - Angèle Sequeira
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
| | - Alicia Defay-Stinat
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
| | - Claudio Plaisant
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France; (C.P.); (E.L.); (L.B.)
| | - Shahram Mesdaghi
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; (S.M.); (D.R.)
- Computational Biology Facility, MerseyBio, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK
| | - Daniel Rigden
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK; (S.M.); (D.R.)
| | - Sophie Javerzat
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
| | - Eulalie Lasseaux
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France; (C.P.); (E.L.); (L.B.)
| | - Laetitia Bourgeade
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France; (C.P.); (E.L.); (L.B.)
| | | | - Hélène Dollfus
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Strasbourg, 67091 Strasbourg, France;
| | - Smail Hadj-Rabia
- Service de Dermatologie, Hôpital Necker-Enfants Malades, 75015 Paris, France;
| | - Fanny Morice-Picard
- Service de Dermatologie, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France;
| | | | | | - Vasily Smirnov
- Service d’Exploration Fonctionnelle de la Vision et de Neuro-Ophtalmologie, Centre Hospitalier Universitaire de Lille, 59037 Lille, France;
| | - Ousmane Sylla
- Infirmerie Hôpital Militaire, Bamako BP 236, Mali; (M.K.S.); (O.S.)
| | - Vincent Michaud
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France; (C.P.); (E.L.); (L.B.)
| | - Benoit Arveiler
- Laboratoire Maladies Rares, Génétique et Métabolisme, Bordeaux University, INSERM U1211, 33076 Bordeaux, France; (M.D.); (C.C.); (E.M.); (A.S.); (A.D.-S.); (S.J.); (V.M.)
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Bordeaux, 33076 Bordeaux, France; (C.P.); (E.L.); (L.B.)
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Kohli S, Saxena R, Puri RD, Bijarnia Mahay S, Pal S, Dubey S, Arora V, Verma I. The molecular landscape of oculocutaneous albinism in India and its therapeutic implications. Eur J Hum Genet 2023:10.1038/s41431-023-01496-5. [PMID: 38030918 DOI: 10.1038/s41431-023-01496-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 10/14/2023] [Accepted: 11/08/2023] [Indexed: 12/01/2023] Open
Abstract
Oculocutaneous albinism is an inherited disorder of melanin biosynthesis, characterized by absent or reduced pigmentation of the skin, hair, and eyes. Molecular alterations of genes that cause non-syndromic albinism in Asian Indians are poorly characterized. This information would be useful for developing therapies for this disorder. We analyzed 164 persons with non-syndromic albinism, belonging to unrelated families from all parts of India, for molecular changes in the causative genes. Subjects with white hair, white skin, and red iris had their tyrosinase gene sequenced and were also tested by MLPA for deletions/duplications. Subjects with negative results or with darker skin, golden/brown or darker hair had sequencing of TYR, P, TYRP1, SLC45A2 and GPR143 genes. Pathogenic variants in TYR (OCA1) were observed in 139 (84.7%) patients, in the P gene (OCA2) in 20 (12.2%), in TYRP1 (OCA3) in two (1.2%), in SLC45A2 (OCA 4) in one (0.61%), and in GPR143 (X-linked ocular albinism) in two (1.2%) patients. Of 278 alleles with variants in TYR, 179 (64.3%) alleles had (p.R278*) alteration, suggesting the possibility of therapy with a stop codon readthrough molecule. We report 20 patients with 13 disease associated variants in the P gene and 18 novel pathogenic variants in TYR, P, TYRP1, SLC45A2 and GPR143 genes. The data are compared with those reported from India, Pakistan and rest of the world. The therapeutic options in albinism are briefly described, opening this field for future therapies.
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Affiliation(s)
- Sudha Kohli
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India.
| | - Renu Saxena
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India
| | - Ratna Dua Puri
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India
| | - Sunita Bijarnia Mahay
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India
| | - Swasti Pal
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India
| | - Sudhisha Dubey
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India
| | - Veronica Arora
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India
| | - Ishwar Verma
- Institute of Medical Genetics and Genomics, Ganga Ram Institute of Postgraduate Medical Education and Research, Sir Ganga Ram Hospital, New Delhi, 110060, India.
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Chen X, Fang Z, Pang T, Li D, Lei J, Jiang W, Li H. Identification of novel variations of oculocutaneous albinism type 2 with Prader-Willi syndrome/Angelman syndrome in two Chinese families. Front Genet 2023; 14:1135698. [PMID: 36950135 PMCID: PMC10025288 DOI: 10.3389/fgene.2023.1135698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Accepted: 02/15/2023] [Indexed: 03/08/2023] Open
Abstract
Objective: Oculocutaneous albinism (OCA) is an autosomal recessive disorder caused by a variety of genomic variations. Our aim is to identify the molecular basis of OCA in two families and lay the foundation for prenatal diagnosis. Methods: Four types of OCA-causing mutations in the TYR, p, TYRP1, or SLC45A2 genes were screened. Linkage analysis was performed because the mutations found in the p gene violated the laws of classical Mendelian heredity. Primer-walking sequencing combined with microsatellite and single-nucleotide polymorphism analysis was used to ascertain deletion ranges. Bioinformatics methods were used to assess the pathogenicity of the new mutations. Results: Proband 1 was diagnosed as OCA2 with Prader-Willi syndrome (PWS) due to a novel atypical paternal deletion (chromosome 15: 22330347-26089649) and a pathogenic mutation, c.1327G>A (Val443Ile), in the p gene of the maternal chromosome. The prenatal diagnosis results for family 1 indicated the fetus was a heterozygous carrier (c.1327G>A in the p gene) with a normal phenotype. Proband 2 was diagnosed as OCA2 with Angelman syndrome (AS) due to a typical maternal deletion of chromosome 15q11-q13 and a novel mutation, c.1514T>C (Phe505Ser), in the p gene of the paternal chromosome. This novel mutation c.1514T>C (Phe505Ser) in the p gene was predicted as a pathogenic mutation. Conclusion: Our study has shown clear genotype-phenotype correlations in patients affected by distinct deletions of the PWS or AS region and missense mutations in the p gene. Our results have enriched the mutation spectrum of albinism diseases and provided insights for more accurate diagnosis and genetic counseling.
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Affiliation(s)
- XiaoFei Chen
- Maternity and Child Care Center of Dezhou, DeZhou, China
- Department of Medical Genetics, Zhongshan School of Medicine, Guangzhou, China
| | - ZiShui Fang
- Department of Medical Genetics, Zhongshan School of Medicine, Guangzhou, China
- Beijing Key Laboratory of Urogenital Diseases (Male) Molecular Diagnosis and Treatment Center, National Urological Cancer Center, Department of Urology, Peking University First Hospital, Institution of Urology, Peking University, Beijing, China
| | - Ting Pang
- Department of Medical Genetics, Zhongshan School of Medicine, Guangzhou, China
| | - DongZhi Li
- Prenatal Diagnosis Center, Guangzhou Women and Children’s Medical Center, Guangzhou, China
| | - Jie Lei
- Department of Medical Genetics, Zhongshan School of Medicine, Guangzhou, China
- Shenzhen Nanshan Maternity and Child Healthcare Hospital, Shenzhen, China
- *Correspondence: Jie Lei, ; WeiYing Jiang, ; HongYi Li,
| | - WeiYing Jiang
- Department of Medical Genetics, Zhongshan School of Medicine, Guangzhou, China
- *Correspondence: Jie Lei, ; WeiYing Jiang, ; HongYi Li,
| | - HongYi Li
- Department of Medical Genetics, Zhongshan School of Medicine, Guangzhou, China
- *Correspondence: Jie Lei, ; WeiYing Jiang, ; HongYi Li,
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Laetitia MM, Veronique K, Mamy NZ, Cathy SM, Aimé L, Race V, Prosper LT, Devriendt K. Molecular genetic characterization of Congolese patients with oculocutaneous albinism. Eur J Med Genet 2022; 65:104611. [PMID: 36116698 DOI: 10.1016/j.ejmg.2022.104611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 08/16/2022] [Accepted: 09/06/2022] [Indexed: 11/03/2022]
Abstract
BACKGROUND Oculocutaneous albinism (OCA) is an autosomal recessive genetic disorder associated with reduced or absent pigmentation in the skin, hair and eyes. OCA type 2 (OCA2) is the most common type in Sub-Saharan Africa, related to a recurrent 2.7 kb intragenic deletion. Genomic data from Congolese patients are lacking. We aimed to describe genetic causes of OCA2 in a cohort of Congolese persons with OCA, and explore possible genotype-phenotype correlations. METHODS A cross sectional study was conducted from January 2015 to December 2017 in Kinshasa, Democratic Republic of Congo (DRC). 165 Congolese unrelated families with non-syndromic OCA, identified through patients' associations, consented to participate to this study. All index cases were tested for the known 2.7 kb deletion involving the exon 7 of the OCA2 gene. Patients heterozygous for the deletion underwent Sanger sequencing of all exons and flanking sequences in the OCA2 gene. Family segregation was performed for candidate pathogenic variants. RESULTS The 2.7 kb deletion in the OCA2 gene was identified in 136/165 (82.4%) index cases, including 113 (68.5%) homozygotes and 23 (13.9%) heterozygotes. Sanger sequencing identified a pathogenic or likely pathogenic variant in the OCA2 gene in 12 out of 23 heterozygotes investigated (52.1%). Segregation analysis allowed us to locate the point mutation on the trans allele in the three patients from whom parental DNA was available. CONCLUSION The OCA2 2.7 kb deletion is the major cause of non-syndromic OCA in Congolese patients recruited in this study, confirming results from other Sub-Saharan African populations. Several additional mutations were detected in OCA patient's heterozygote for the deletion, with to date no evidence for a second frequent founder mutation. The confirmation of a single mutation as the major cause will facilitate genetic counselling in this country.
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Affiliation(s)
- Mavinga Mpola Laetitia
- Department of Pediatrics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The; Centre for Human Genetics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The.
| | - Kakiese Veronique
- Department of Dermatology, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The
| | - Ngole Zita Mamy
- Centre for Human Genetics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The
| | - Songo Mbodo Cathy
- Centre for Human Genetics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The
| | - Lumaka Aimé
- Department of Pediatrics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The; Centre for Human Genetics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The; Laboratory of Human Genetics, GIGA-R, University of Liège, Belgium
| | - Valerie Race
- Center for Human Genetics, University Hospital, KU Leuven, Belgium
| | - Lukusa Tshilobo Prosper
- Department of Pediatrics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The; Centre for Human Genetics, Faculty of Medicine, University of Kinshasa, Democratic Republic of the Congo, The; Center for Human Genetics, University Hospital, KU Leuven, Belgium
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Aquaron R, Lasseaux E, Kelekele J, Bonello-Palot N, Badens C, Arveiler B, Tshilolo L. Co-occurrence of oculocutaneous albinism type 2 and mild sickle cell disease explained by HbS/βthal genotype in an individual from the Democratic Republic of Congo. Eur J Med Genet 2022; 65:104594. [PMID: 35964929 DOI: 10.1016/j.ejmg.2022.104594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 07/26/2022] [Accepted: 08/07/2022] [Indexed: 11/03/2022]
Abstract
Oculocutaneous albinism type 2 (OCA2) is a pigmentation disorder characterized by hypopigmentation of the skin, hair and eyes and ocular features. Sickle cell disease (SCD) is caused either by homozygosity of the beta globin gene variant c.20A > T/p.Glu6Val giving rise to severe anemia or by combined abnormal hemoglobins (HbS/βthal) leading to mild SCD. We report a 45 years old female patient from the Democratic Republic of Congo affected with these two disorders. She presented with creamy white skin and numerous pigmented patches called dendritic freckles, nystagmus, foveal hypoplasia grade 2, photophobia and very poor visual acuity. Sequencing of the OCA2 gene identified the common exon 7 deletion and a new pathogenic variant c.1444A > C/p.Thr482Pro. She had mild SCD with a total Hb level of 101 g/l. Hbβ sequencing identified variants c.20A > T giving rise to HbS and c.315 + 1 G > A characteristic of β-thalassemia. A heterozygous 3.7 kb deletion of the α globin gene was also found. The combined Hbβ/α globin genotype explains the mild SCD phenotype. Co-occurrence of OCA2 and SCD raises the question whether the patient's phenotype simply results from the addition of the two diseases' phenotypes or whether interaction between the two diseases modulates the phenotype of each other.
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Affiliation(s)
- Robert Aquaron
- Faculté de Médecine, Aix-Marseille Université, 27 Boulevard Jean Moulin, 13385, Marseille, cedex 5, France
| | - Eulalie Lasseaux
- Service de Génétique Médicale, CHU de Bordeaux, Hôpital Pellegrin, 1 place Amelie Raba Léon, 33076, Bordeaux Cedex, France
| | - Joseph Kelekele
- Cliniques Universitaires de Kinshasa, Département d'Ophtalmologie. UNIKIN. Mont Amba, Kinshasa, Democratic Republic of the Congo, The
| | | | - Catherine Badens
- Laboratoire de Génétique Moléculaire, Hôpital d'enfants de la Timone, Marseille, France
| | - Benoit Arveiler
- Service de Génétique Médicale, CHU de Bordeaux, Hôpital Pellegrin, 1 place Amelie Raba Léon, 33076, Bordeaux Cedex, France; Laboratoire Maladies Rares, Génétique et Métabolisme, INSERM U 1211, Université de Bordeaux, France.
| | - Leon Tshilolo
- Centre Hospitalier Monkole, CEFA/ Institut de Recherche Biomédicale, Mont-Ngafula, BP 817, Kinshasa, Democratic Republic of the Congo, The
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Kromberg JGR, Kerr R. Oculocutaneous albinism in southern Africa: Historical background, genetic, clinical and psychosocial issues. Afr J Disabil 2022; 11:877. [PMID: 36353393 PMCID: PMC9639357 DOI: 10.4102/ajod.v11i0.877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 05/29/2022] [Indexed: 05/09/2023] Open
Abstract
Albinism is an inherited condition associated with significant depigmentation of the skin, hair and eyes. It occurs in every population with varying frequency, and narratives of people with albinism have been recorded since 200 BC. In southern Africa albinism is common, about 1 in 4000 people are affected, but it remains a poorly understood condition surrounded by myths and superstition. This article provides a historical background on oculocutaneous albinism (OCA) in southern Africa and presents relevant information from the literature regarding epidemiology, genetics and genetic counselling, health, psychosocial and cultural issues, and medical care. There are several recessively inherited types of OCA and a mutation, responsible for about 80% of South African variants, has been identified in OCA type 2. The physical characteristics associated with albinism, that is, sun-sensitive skin and low vision, can be managed. However, people with OCA in Africa also experience psychosocial issues, such as discrimination, because of the various superstitious beliefs and attitudes held in the community. Management should include medical care for health problems, appropriate adjustment of the schooling context and genetic counseling. In addition, widespread public awareness programmes are required to increase the knowledge of the genetic causes of OCA and of the nature of genetic counselling, to address the negative attitudes in the community, to reduce the marginalisation and stigmatization of people with albinism and to improve their quality of life.
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Affiliation(s)
- Jennifer G R Kromberg
- Department of Human Genetics, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg, South Africa
| | - Robyn Kerr
- Department of Human Genetics, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg, South Africa
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Loftus SK, Lundh L, Watkins-Chow DE, Baxter LL, Pairo-Castineira E, Nisc Comparative Sequencing Program, Jackson IJ, Oetting WS, Pavan WJ, Adams DR. A custom capture sequence approach for oculocutaneous albinism identifies structural variant alleles at the OCA2 locus. Hum Mutat 2021; 42:1239-1253. [PMID: 34246199 DOI: 10.1002/humu.24257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/02/2021] [Accepted: 06/24/2021] [Indexed: 11/09/2022]
Abstract
Oculocutaneous albinism (OCA) is a heritable disorder of pigment production that manifests as hypopigmentation and altered eye development. Exon sequencing of known OCA genes is unsuccessful in producing a complete molecular diagnosis for a significant number of affected individuals. We sequenced the DNA of individuals with OCA using short-read custom capture sequencing that targeted coding, intronic, and noncoding regulatory regions of known OCA genes, and genome-wide association study-associated pigmentation loci. We identified an OCA2 complex structural variant (CxSV), defined by a 143 kb inverted segment reintroduced in intron 1, upstream of the native location. The corresponding CxSV junctions were observed in 11/390 probands screened. The 143 kb CxSV presents in one family as a copy number variant duplication for the 143 kb region. In the remaining 10/11 families, the 143 kb CxSV acquired an additional 184 kb deletion across the same region, restoring exons 3-19 of OCA2 to a copy-number neutral state. Allele-associated haplotype analysis found rare SNVs rs374519281 and rs139696407 are linked with the 143 kb CxSV in both OCA2 alleles. For individuals in which customary molecular evaluation does not reveal a biallelic OCA diagnosis, we recommend preliminary screening for these haplotype-associated rare variants, followed by junction-specific validation for the OCA2 143 kb CxSV.
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Affiliation(s)
- Stacie K Loftus
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Linnea Lundh
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Dawn E Watkins-Chow
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Laura L Baxter
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Erola Pairo-Castineira
- Roslin Institute, University of Edinburgh, Easter Bush, Edinburgh, UK.,MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, Western General Hospital, University of Edinburgh, Edinburgh, UK
| | | | - Ian J Jackson
- Roslin Institute, University of Edinburgh, Easter Bush, Edinburgh, UK.,MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, Western General Hospital, University of Edinburgh, Edinburgh, UK
| | - William S Oetting
- Department of Experimental and Clinical Pharmacology, University of Minnesota, Minneapolis, Minnesota, USA
| | - William J Pavan
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - David R Adams
- Office of the Clinical Director, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA
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9
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Fernández A, Hayashi M, Garrido G, Montero A, Guardia A, Suzuki T, Montoliu L. Genetics of non-syndromic and syndromic oculocutaneous albinism in human and mouse. Pigment Cell Melanoma Res 2021; 34:786-799. [PMID: 33960688 DOI: 10.1111/pcmr.12982] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/21/2021] [Accepted: 04/26/2021] [Indexed: 01/12/2023]
Abstract
Oculocutaneous albinism (OCA) is the most frequent presentation of albinism, a heterogeneous rare genetic condition generally associated with variable alterations in pigmentation and with a profound visual impairment. There are non-syndromic and syndromic types of OCA, depending on whether the gene product affected impairs essentially the function of melanosomes or, in addition, that of other lysosome-related organelles (LROs), respectively. Syndromic OCA can be more severe and associated with additional systemic consequences, beyond pigmentation and vision alterations. In addition to OCA, albinism can also be presented without obvious skin and hair pigmentation alterations, in ocular albinism (OA), and a related genetic condition known as foveal hypoplasia, optic nerve decussation defects, and anterior segment dysgenesis (FHONDA). In this review, we will focus only in the genetics of skin pigmentation in OCA, both in human and mouse, updating our current knowledge on this subject.
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Affiliation(s)
- Almudena Fernández
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.,CIBERER-ISCIII, Madrid, Spain
| | - Masahiro Hayashi
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Gema Garrido
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.,CIBERER-ISCIII, Madrid, Spain
| | - Andrea Montero
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.,CIBERER-ISCIII, Madrid, Spain
| | - Ana Guardia
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.,CIBERER-ISCIII, Madrid, Spain
| | - Tamio Suzuki
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Lluis Montoliu
- Department of Molecular and Cellular Biology, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain.,CIBERER-ISCIII, Madrid, Spain
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10
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Almarri MA, Bergström A, Prado-Martinez J, Yang F, Fu B, Dunham AS, Chen Y, Hurles ME, Tyler-Smith C, Xue Y. Population Structure, Stratification, and Introgression of Human Structural Variation. Cell 2020; 182:189-199.e15. [PMID: 32531199 PMCID: PMC7369638 DOI: 10.1016/j.cell.2020.05.024] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 03/04/2020] [Accepted: 05/12/2020] [Indexed: 02/07/2023]
Abstract
Structural variants contribute substantially to genetic diversity and are important evolutionarily and medically, but they are still understudied. Here we present a comprehensive analysis of structural variation in the Human Genome Diversity panel, a high-coverage dataset of 911 samples from 54 diverse worldwide populations. We identify, in total, 126,018 variants, 78% of which were not identified in previous global sequencing projects. Some reach high frequency and are private to continental groups or even individual populations, including regionally restricted runaway duplications and putatively introgressed variants from archaic hominins. By de novo assembly of 25 genomes using linked-read sequencing, we discover 1,643 breakpoint-resolved unique insertions, in aggregate accounting for 1.9 Mb of sequence absent from the GRCh38 reference. Our results illustrate the limitation of a single human reference and the need for high-quality genomes from diverse populations to fully discover and understand human genetic variation.
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Affiliation(s)
| | - Anders Bergström
- Wellcome Sanger Institute, Hinxton CB10 1SA, UK; The Francis Crick Institute, London NW1 1AT, UK
| | | | | | - Beiyuan Fu
- Wellcome Sanger Institute, Hinxton CB10 1SA, UK
| | - Alistair S Dunham
- Wellcome Sanger Institute, Hinxton CB10 1SA, UK; EMBL-EBI, Hinxton CB10 1SD, UK
| | - Yuan Chen
- Wellcome Sanger Institute, Hinxton CB10 1SA, UK
| | | | | | - Yali Xue
- Wellcome Sanger Institute, Hinxton CB10 1SA, UK.
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11
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Kon T, Omori Y, Fukuta K, Wada H, Watanabe M, Chen Z, Iwasaki M, Mishina T, Matsuzaki SIS, Yoshihara D, Arakawa J, Kawakami K, Toyoda A, Burgess SM, Noguchi H, Furukawa T. The Genetic Basis of Morphological Diversity in Domesticated Goldfish. Curr Biol 2020; 30:2260-2274.e6. [PMID: 32392470 DOI: 10.1016/j.cub.2020.04.034] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 03/13/2020] [Accepted: 04/15/2020] [Indexed: 10/24/2022]
Abstract
Although domesticated goldfish strains exhibit highly diversified phenotypes in morphology, the genetic basis underlying these phenotypes is poorly understood. Here, based on analysis of transposable elements in the allotetraploid goldfish genome, we found that its two subgenomes have evolved asymmetrically since a whole-genome duplication event in the ancestor of goldfish and common carp. We conducted whole-genome sequencing of 27 domesticated goldfish strains and wild goldfish. We identified more than 60 million genetic variations and established a population genetic structure of major goldfish strains. Genome-wide association studies and analysis of strain-specific variants revealed genetic loci associated with several goldfish phenotypes, including dorsal fin loss, long-tail, telescope-eye, albinism, and heart-shaped tail. Our results suggest that accumulated mutations in the asymmetrically evolved subgenomes led to generation of diverse phenotypes in the goldfish domestication history. This study is a key resource for understanding the genetic basis of phenotypic diversity among goldfish strains.
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Affiliation(s)
- Tetsuo Kon
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
| | - Yoshihiro Omori
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan.
| | - Kentaro Fukuta
- Center for Genome Informatics, Joint Support-Center for Data Science Research, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka 411-8540, Japan
| | - Hironori Wada
- College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
| | - Masakatsu Watanabe
- Laboratory of Pattern Formation, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka
| | - Zelin Chen
- Translational and Functional Genomics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Miki Iwasaki
- College of Liberal Arts and Sciences, Kitasato University, Sagamihara, Kanagawa, Japan
| | - Tappei Mishina
- Laboratory of Animal Ecology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | | | - Daiki Yoshihara
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
| | - Jumpei Arakawa
- Yatomi Station, Aichi Fisheries Research Institute, Yatomi, Aichi, Japan
| | - Koichi Kawakami
- Laboratory of Molecular and Developmental Biology, National Institute of Genetics, and Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima, Japan
| | - Atsushi Toyoda
- Comparative Genomics Laboratory, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan
| | - Shawn M Burgess
- Translational and Functional Genomics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Hideki Noguchi
- Center for Genome Informatics, Joint Support-Center for Data Science Research, Research Organization of Information and Systems, Yata 1111, Mishima, Shizuoka 411-8540, Japan; Advanced Genomics Center, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan
| | - Takahisa Furukawa
- Laboratory for Molecular and Developmental Biology, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
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12
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Albinism: epidemiology, genetics, cutaneous characterization, psychosocial factors. An Bras Dermatol 2019; 94:503-520. [PMID: 31777350 PMCID: PMC6857599 DOI: 10.1016/j.abd.2019.09.023] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Accepted: 09/09/2019] [Indexed: 11/20/2022] Open
Abstract
Oculocutaneous albinism is an autosomal recessive disease caused by the complete absence or decrease of melanin biosynthesis in melanocytes. Due to the reduction or absence of melanin, albinos are highly susceptible to the harmful effects of ultraviolet radiation and are at increased risk of actinic damage and skin cancer. In Brazil, as in other parts of the world, albinism remains a little known disorder, both in relation to epidemiological data and to phenotypic and genotypic variation. In several regions of the country, individuals with albinism have no access to resources or specialized medical care, and are often neglected and deprived of social inclusion. Brazil is a tropical country, with a high incidence of solar radiation during the year nationwide. Consequently, actinic damage and skin cancer occur early and have a high incidence in this population, often leading to premature death. Skin monitoring of these patients and immediate therapeutic interventions have a positive impact in reducing the morbidity and mortality associated with this condition. Health education is important to inform albinos and their families, the general population, educators, medical professionals, and public agencies about the particularities of this genetic condition. The aim of this article is to present a review of the epidemiological, clinical, genetic, and psychosocial characteristics of albinism, with a focus in skin changes caused by this rare pigmentation disorder.
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13
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Zhong Z, Gu L, Zheng X, Ma N, Wu Z, Duan J, Zhang J, Chen J. Comprehensive analysis of spectral distribution of a large cohort of Chinese patients with non-syndromic oculocutaneous albinism facilitates genetic diagnosis. Pigment Cell Melanoma Res 2019; 32:672-686. [PMID: 31077556 PMCID: PMC6852118 DOI: 10.1111/pcmr.12790] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 03/31/2019] [Accepted: 05/05/2019] [Indexed: 12/25/2022]
Abstract
Non-syndromic oculocutaneous albinism (nsOCA) is a group of genetically heterogeneous autosomal recessive disorders with complete lack or decrease pigmentation in skin, hair, and eyes. TYR, OCA2, TYRP1, SLC45A2, SLC24A5, and LRMDA were reported to cause OCA1-4 and OCA6-7, respectively. By sequencing all the known nsOCA genes in 114 unrelated Chinese nsOCA patients combined with In silico analyses, splicing assay, and classification of variants according to the standards and guidelines of American College of Medical Genetics and Genomics, we detected seventy-one different OCA-causing variants separately in TYR, OCA2, SLC45A2, and SLC24A5, including thirty-one novel variants (13 in TYR, 11 in OCA2, and 7 in SLC45A2). This study shows that OCA1 is the most common (75/114) and OCA2 ranks the second most common (16/114) in Chinese. 99 patients of our cohort were caused by variants of all the known nsOCA genes. Cutaneous phenotypes of OCA1, OCA2, and OCA4 patients were shown in this study. The second OCA6 case in China was identified here. These data expand the spectrum of OCA variants as well phenotype and facilitate clinical implement of Chinese OCA patients.
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Affiliation(s)
- Zilin Zhong
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China.,Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai, China
| | - Li Gu
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiujie Zheng
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China
| | - Nengjun Ma
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China
| | - Zehua Wu
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China
| | - Juan Duan
- Department of Auxiliary Reproductive, Jiujiang Maternal and Child Health Hospital, Jiujiang, China
| | - Jun Zhang
- Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai, China
| | - Jianjun Chen
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China.,Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai, China
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14
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Abstract
Human skin and hair color are visible traits that can vary dramatically within and across ethnic populations. The genetic makeup of these traits-including polymorphisms in the enzymes and signaling proteins involved in melanogenesis, and the vital role of ion transport mechanisms operating during the maturation and distribution of the melanosome-has provided new insights into the regulation of pigmentation. A large number of novel loci involved in the process have been recently discovered through four large-scale genome-wide association studies in Europeans, two large genetic studies of skin color in Africans, one study in Latin Americans, and functional testing in animal models. The responsible polymorphisms within these pigmentation genes appear at different population frequencies, can be used as ancestry-informative markers, and provide insight into the evolutionary selective forces that have acted to create this human diversity.
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Affiliation(s)
- William J Pavan
- Genetic Disease Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA;
| | - Richard A Sturm
- Dermatology Research Centre, The University of Queensland Diamantina Institute, The University of Queensland, Brisbane, Queensland 4102, Australia;
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15
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Onojafe IF, Megan LH, Melch MG, Aderemi JO, Alur RP, Abu-Asab MS, Chan CC, Bernardini IM, Albert JS, Cogliati T, Adams DR, Brooks BP. Minimal Efficacy of Nitisinone Treatment in a Novel Mouse Model of Oculocutaneous Albinism, Type 3. Invest Ophthalmol Vis Sci 2019; 59:4945-4952. [PMID: 30347088 PMCID: PMC6181301 DOI: 10.1167/iovs.16-20293] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Purpose Oral nitisinone has been shown to increase fur and ocular pigmentation in a mouse model of oculocutaneous albinism (OCA) due to hypomorphic mutations in tyrosinase (TYR), OCA1B. This study determines if nitisinone can improve ocular and/or fur pigmentation in a mouse model of OCA type 3 (OCA3), caused by mutation of the tyrosinase-related protein 1 (Tyrp1) gene. Methods Mice homozygous for a null allele in the Tyrp1 gene (C57BL/6J-Tyrp1 b-J/J) were treated with 8 mg/kg nitisinone or vehicle every other day by oral gavage. Changes in fur and ocular melanin pigmentation were monitored. Mature ocular melanosome number and size were quantified in pigmented ocular structures by electron microscopy. Results C57BL/6J-Tyrp1 b-J/J mice carry a novel c.403T>A; 404delG mutation in Tyrp1, predicted to result in premature truncation of the TYRP1 protein. Nitisinone treatment resulted in an approximately 7-fold increase in plasma tyrosine concentrations without overt toxicity. After 1 month of treatment, no change in the color of fur or pigmented ocular structures was observed. The distribution of melanosome cross-sectional area was unchanged in ocular tissues. There was no significant difference in the number of pigmented melanosomes in the RPE/choroid of nitisinone-treated and control groups. However, there was a significant difference in the number of pigmented melanosomes in the iris. Conclusions Treatment of a mouse model of OCA3 with oral nitisinone did not have a favorable clinical effect on melanin production and minimally affected the number of pigmented melanosomes in the iris stroma. As such, treatment of OCA3 patients with nitisinone is unlikely to be therapeutic.
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Affiliation(s)
- Ighovie F Onojafe
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Lucyanne H Megan
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Madeline G Melch
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Joseph O Aderemi
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Ramakrishna P Alur
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Mones S Abu-Asab
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Chi-Chao Chan
- Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Isa M Bernardini
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Jessica S Albert
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Tiziana Cogliati
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - David R Adams
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Brian P Brooks
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
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16
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Singh BK, Kim EK. P-Protein: A Novel Target for Skin-whitening Agent. BIOTECHNOL BIOPROC E 2019. [DOI: 10.1007/s12257-018-0241-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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17
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Adams DR, Menezes S, Jauregui R, Valivullah ZM, Power B, Abraham M, Jeffrey BG, Garced A, Alur RP, Cunningham D, Wiggs E, Merideth MA, Chiang PW, Bernstein S, Ito S, Wakamatsu K, Jack RM, Introne WJ, Gahl WA, Brooks BP. One-year pilot study on the effects of nitisinone on melanin in patients with OCA-1B. JCI Insight 2019; 4:124387. [PMID: 30674731 PMCID: PMC6413781 DOI: 10.1172/jci.insight.124387] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 12/06/2018] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND. Oculocutaneous albinism (OCA) results in reduced melanin synthesis, skin hypopigmentation, increased risk of UV-induced malignancy, and developmental eye abnormalities affecting vision. No treatments exist. We have shown that oral nitisinone increases ocular and fur pigmentation in a mouse model of one form of albinism, OCA-1B, due to hypomorphic mutations in the Tyrosinase gene. METHODS. In this open-label pilot study, 5 adult patients with OCA-1B established baseline measurements of iris, skin, and hair pigmentation and were treated over 12 months with 2 mg/d oral nitisinone. Changes in pigmentation and visual function were evaluated at 3-month intervals. RESULTS. The mean change in iris transillumination, a marker of melanin, from baseline was 1.0 ± 1.54 points, representing no change. The method of iris transillumination grading showed a high intergrader reliability (intraclass correlation coefficient ≥ 0.88 at each visit). The number of letters read (visual acuity) improved significantly at month 12 for both eyes (right eye, OD, mean 4.2 [95% CI, 0.3, 8.1], P = 0.04) and left eye (OS, 5 [1.0, 9.1], P = 0.003). Skin pigmentation on the inner bicep increased (M index increase = 1.72 [0.03, 3.41], P = 0.047). Finally, hair pigmentation increased by both reflectometry (M index [17.3 {4.4, 30.2}, P = 0.01]) and biochemically. CONCLUSION. Nitisinone did not result in an increase in iris melanin content but may increase hair and skin pigmentation in patients with OCA-1B. The iris transillumination grading scale used in this study proved robust, with potential for use in future clinical trials. TRIAL REGISTRATION. ClinicalTrials.gov NCT01838655. FUNDING. Intramural program of the National Eye Institute. Oral nitisinone may improve melanin pigmentation in patients with the OCA-1B form of albinism due to hypomorphic mutations in the tyrosinase gene.
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Affiliation(s)
- David R Adams
- National Human Genome Research Institute, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
| | | | | | - Zaheer M Valivullah
- National Human Genome Research Institute, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
| | - Bradley Power
- National Human Genome Research Institute, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
| | | | | | | | | | | | - Edythe Wiggs
- National Institute of Neurological Disease and Stroke, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
| | - Melissa A Merideth
- National Human Genome Research Institute, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
| | | | - Shanna Bernstein
- Nutrition Department, NIH Clinical Center, Bethesda, Maryland, USA
| | - Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan
| | - Rhona M Jack
- Seattle Children's Hospital, Department of Pathology & Laboratory Medicine, Seattle, Washington, USA
| | - Wendy J Introne
- National Human Genome Research Institute, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
| | - William A Gahl
- National Human Genome Research Institute, NIH, Department of Health and Human Services, Bethesda, Maryland, USA
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18
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Mutational analysis of a Chinese family with oculocutaneous albinism type 2. Oncotarget 2017; 8:70345-70355. [PMID: 29050284 PMCID: PMC5642559 DOI: 10.18632/oncotarget.19697] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/01/2017] [Indexed: 11/25/2022] Open
Abstract
Oculocutaneous albinism (OCA) is an autosomal recessive disorder characterized by hypopigmentation of the skin, hair, and eyes accompanied with ophthalmologic abnormalities. Molecular genetic test can confirm the diagnosis of the four subtypes of OCA (OCA1-4). Herein, we report a Chinese family with two patients affected by OCA. Mutations of TYR, OCA2, TYRP1, and SLC45A2 were examined by using PCR-sequencing. Large deletions or duplications of TYR and OCA2 were examined by Multiplex Ligation-dependent Probe Amplification (MLPA) assay. Compound heterozygous mutations of OCA2, (c.808-3C>G and c.2080-2A>G), were identified in both patients characterized with yellow hair and milky skin, heterochromia iridis, and nystagmus. Several computer-assisted approaches predicted that c.808-3C>G and c.2080-2A>G in OCA2 might potentially be pathogenic splicing mutations. No exon rearrangement (deletion/duplication) of TYR and OCA2 was observed in the patients by MLPA analysis. This study suggests that compound heterozygous mutations, (c.808-3C>G and c.2080-2A>G), in OCA2 may be responsible for partial clinical manifestations of OCA.
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19
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Aquaron R. Passé, présent et futur de l’albinisme humain. Presse Med 2017; 46:645-647. [DOI: 10.1016/j.lpm.2017.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 04/11/2017] [Indexed: 11/25/2022] Open
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20
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Fábos B, Farkas K, Tóth L, Sulák A, Tripolszki K, Tihanyi M, Németh R, Vas K, Csoma Z, Kemény L, Széll M, Nagy N. Delineating the genetic heterogeneity of OCA in Hungarian patients. Eur J Med Res 2017. [PMID: 28629449 PMCID: PMC5477306 DOI: 10.1186/s40001-017-0262-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Oculocutaneous albinism (OCA) is a clinically and genetically heterogenic group of pigmentation abnormalities characterized by variable hair, skin, and ocular hypopigmentation. Six known genes and a locus on human chromosome 4q24 have been implicated in the etiology of isolated OCA forms (OCA 1-7). METHODS The most frequent OCA types among Caucasians are OCA1, OCA2, and OCA4. We aimed to investigate genes responsible for the development of these OCA forms in Hungarian OCA patients (n = 13). Mutation screening and polymorphism analysis were performed by direct sequencing on TYR, OCA2, SLC45A2 genes. RESULTS Although the clinical features of the investigated Hungarian OCA patients were identical, the molecular genetic data suggested OCA1 subtype in eight cases and OCA4 subtype in two cases. The molecular diagnosis was not clearly identifiable in three cases. In four patients, two different heterozygous known pathogenic or predicted to be pathogenic mutations were present. Seven patients had only one pathogenic mutation, which was associated with non-pathogenic variants in six cases. In two patients no pathogenic mutation was identified. CONCLUSIONS Our results suggest that the concomitant screening of the non-pathogenic variants-which alone do not cause the development of OCA, but might have clinical significance in association with a pathogenic variant-is important. Our results also show significant variation in the disease spectrum compared to other populations. These data also confirm that the concomitant analysis of OCA genes is critical, providing new insights to the phenotypic diversity of OCA and expanding the mutation spectrum of OCA genes in Hungarian patients.
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Affiliation(s)
- Beáta Fábos
- Mór Kaposi Teaching Hospital of the Somogy County, Kaposvár, Hungary
| | - Katalin Farkas
- MTA-SZTE Dermatological Research Group, University of Szeged, Szeged, Hungary
| | - Lola Tóth
- Department of Medical Genetics, University of Szeged, 4 Somogyi Bela Street, 6720, Szeged, Hungary
| | - Adrienn Sulák
- Department of Medical Genetics, University of Szeged, 4 Somogyi Bela Street, 6720, Szeged, Hungary
| | - Kornélia Tripolszki
- Department of Medical Genetics, University of Szeged, 4 Somogyi Bela Street, 6720, Szeged, Hungary
| | - Mariann Tihanyi
- Genetic Laboratory, Hospital of Zala County, Zalaegerszeg, Hungary
| | - Réka Németh
- Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary
| | - Krisztina Vas
- Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary
| | - Zsanett Csoma
- Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary
| | - Lajos Kemény
- MTA-SZTE Dermatological Research Group, University of Szeged, Szeged, Hungary.,Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary
| | - Márta Széll
- MTA-SZTE Dermatological Research Group, University of Szeged, Szeged, Hungary.,Department of Medical Genetics, University of Szeged, 4 Somogyi Bela Street, 6720, Szeged, Hungary
| | - Nikoletta Nagy
- MTA-SZTE Dermatological Research Group, University of Szeged, Szeged, Hungary. .,Department of Medical Genetics, University of Szeged, 4 Somogyi Bela Street, 6720, Szeged, Hungary. .,Department of Dermatology and Allergology, University of Szeged, Szeged, Hungary.
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Clinical evaluation and molecular screening of a large consecutive series of albino patients. J Hum Genet 2016; 62:277-290. [PMID: 27734839 DOI: 10.1038/jhg.2016.123] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 09/08/2016] [Accepted: 09/10/2016] [Indexed: 12/26/2022]
Abstract
Oculocutaneous albinism (OCA) is characterized by hypopigmentation of the skin, hair and eye, and by ophthalmologic abnormalities caused by a deficiency in melanin biosynthesis. In this study we recruited 321 albino patients and screened them for the genes known to cause oculocutaneous albinism (OCA1-4 and OCA6) and ocular albinism (OA1). Our purpose was to detect mutations and genetic frequencies of the main causative genes, offering to albino patients an exhaustive diagnostic assessment within a multidisciplinary approach including ophthalmological, dermatological, audiological and genetic evaluations. We report 70 novel mutations and the frequencies of the major causative OCA genes that are as follows: TYR (44%), OCA2 (17%), TYRP1 (1%), SLC45A2 (7%) and SLC24A5 (<0.5%). An additional 5% of patients had GPR143 mutations. In 19% of cases, a second reliable mutation was not detected, whereas 7% of our patients remain still molecularly undiagnosed. This comprehensive study of a consecutive series of OCA/OA1 patients allowed us to perform a clinical evaluation of the different OCA forms.
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Brilliant MH. Albinism in Africa: a medical and social emergency. Int Health 2015; 7:223-5. [DOI: 10.1093/inthealth/ihv039] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Accepted: 06/04/2015] [Indexed: 11/13/2022] Open
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McCafferty BK, Wilk MA, McAllister JT, Stepien KE, Dubis AM, Brilliant MH, Anderson JL, Carroll J, Summers CG. Clinical Insights Into Foveal Morphology in Albinism. J Pediatr Ophthalmol Strabismus 2015; 52:167-72. [PMID: 26053207 PMCID: PMC4948980 DOI: 10.3928/01913913-20150427-06] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Accepted: 01/13/2015] [Indexed: 11/20/2022]
Abstract
PURPOSE A hallmark of albinism is foveal hypoplasia. However, literature suggests variable foveal development. This study evaluates the association between ocular phenotype and foveal morphology to demonstrate the broad structural and functional spectrum. METHODS Best-corrected visual acuity (BCVA), nystagmus, angle kappa, stereoacuity, iris transillumination, macular melanin presence, foveal avascular zone, and annular reflex were recorded in 14 patients with albinism. Spectral-domain optical coherence tomography provided macular images. RESULTS The clinical phenotype was broad, with BCVA varying from 20/20 to 20/100. Better BCVA was associated with a preserved foveal avascular zone, annular macular reflex, stereoacuity, and macular melanin. Imaging demonstrated a continuum of foveal development correlating with BCVA. Individuals with a rudimentary pit had normal inner and outer segment lengthening and better BCVA. CONCLUSIONS The spectrum of ocular structure and visual function in albinism is broad, suggesting a possible diagnosis of albinism in a patient with an even more normal clinical presentation.
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MESH Headings
- Adolescent
- Adult
- Aged, 80 and over
- Albinism, Ocular/diagnosis
- Albinism, Ocular/genetics
- Albinism, Ocular/physiopathology
- Albinism, Oculocutaneous/diagnosis
- Albinism, Oculocutaneous/genetics
- Albinism, Oculocutaneous/physiopathology
- Child
- DNA Mutational Analysis
- Depth Perception/physiology
- Evoked Potentials, Visual
- Eye Abnormalities/diagnosis
- Eye Abnormalities/genetics
- Eye Abnormalities/physiopathology
- Eye Proteins/genetics
- Female
- Fovea Centralis/abnormalities
- Fovea Centralis/pathology
- Humans
- Male
- Membrane Proteins/genetics
- Nystagmus, Pathologic/diagnosis
- Phenotype
- Polymerase Chain Reaction
- Prospective Studies
- Tomography, Optical Coherence
- Visual Acuity/physiology
- Young Adult
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Shoji H, Kiniwa Y, Okuyama R, Yang M, Higuchi K, Mori M. A nonsense nucleotide substitution in the oculocutaneous albinism II gene underlies the original pink-eyed dilution allele (Oca2(p)) in mice. Exp Anim 2015; 64:171-9. [PMID: 25736709 PMCID: PMC4427732 DOI: 10.1538/expanim.14-0075] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The original pink-eyed dilution (p) on chromosome 7 is a very old
spontaneous mutation in mice. The oculocutaneous albinism II (Oca2) gene
has previously been identified as the p gene. Oca2
transcripts have been shown to be absent in the skin of SJL/J mice with the original
p mutant allele (Oca2p); however, the
molecular genetic lesion underlying the original Oca2p allele
has never been reported. The NCT mouse (commonly known as Nakano cataract mouse) has a
pink-eyed dilution phenotype, which prompted us to undertake a molecular genetic analysis
of the Oca2 gene of this strain. Our genetic linkage analysis suggests
that the locus for the pink-eyed dilution phenotype of NCT is tightly linked to the
Oca2 locus. PCR cloning and nucleotide sequence analysis indicates that
the NCT mouse has a nonsense nucleotide substitution at exon 7 of the
Oca2 gene. Examination of three mouse strains (NZW/NSlc, SJL/J, and
129X1/SvJJmsSlc) with the original Oca2p allele revealed the
presence of a nonsense nucleotide substitution identical to that in the NCT strain. RT-PCR
analysis revealed that the Oca2 transcripts were absent in the skin of
NCT mice, suggesting intervention of the nonsense-mediated mRNA decay pathway.
Collectively, the data in this study indicate that the nonsense nucleotide substitution in
the Oca2 gene underlies the Oca2p allele. Our
data also indicate that the NCT mouse can be used not only as a cataract model, but also
as a model for human type II oculocutaneous albinism.
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Affiliation(s)
- Haruka Shoji
- Department of Aging Biology, Institute of Pathogenesis and Disease Prevention, Shinshu University Graduate School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan
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Abstract
Oculocutaneous albinism (OCA) is a heterogeneous autosomal recessive genetic disorder that affects melanin synthesis. OCA results in reduced or absent pigmentation in the hair, skin and eyes. Type 1 OCA (OCA1) is the result of tyrosinase (TYR) gene mutations and is a severe disease type. This study investigated TYR mutations in a Chinese cohort with OCA1. This study included two parts: patient genetic study and prenatal genetic diagnosis. A total of 30 OCA1 patients were subjected to TYR gene mutation analysis. Ten pedigrees were included for prenatal genetic diagnosis. A total of 100 unrelated healthy Chinese individuals were genotyped for controls. The coding sequence and the intron/exon junctions of TYR were analysed by bidirectional DNA sequencing. In this study, 20 mutations were identified, four of which were novel. Of these 30 OCA1 patients, 25 patients were TYR compound heterozygous; two patients carried homozygous TYR mutations; and three were heterozygous. Among the ten prenatally genotyped fetuses, three fetuses carried compound heterozygous mutations and seven carried no mutation or only one mutant allele of TYR and appeared normal at birth. In conclusion, we identified four novel TYR mutations and showed that molecular-based prenatal screening to detect TYR mutations in a fetus at risk for OCA1 provided essential information for genetic counselling of couples at risk.
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Kamaraj B, Purohit R. Mutational analysis of oculocutaneous albinism: a compact review. BIOMED RESEARCH INTERNATIONAL 2014; 2014:905472. [PMID: 25093188 PMCID: PMC4100393 DOI: 10.1155/2014/905472] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 06/11/2014] [Indexed: 01/17/2023]
Abstract
Oculocutaneous albinism (OCA) is an autosomal recessive disorder caused by either complete lack of or a reduction of melanin biosynthesis in the melanocytes. The OCA1A is the most severe type with a complete lack of melanin production throughout life, while the milder forms OCA1B, OCA2, OCA3, and OCA4 show some pigment accumulation over time. Mutations in TYR, OCA2, TYRP1, and SLC45A2 are mainly responsible for causing oculocutaneous albinism. Recently, two new genes SLC24A5 and C10orf11 are identified that are responsible to cause OCA6 and OCA7, respectively. Also a locus has been mapped to the human chromosome 4q24 region which is responsible for genetic cause of OCA5. In this paper, we summarized the clinical and molecular features of OCA genes. Further, we reviewed the screening of pathological mutations of OCA genes and its molecular mechanism of the protein upon mutation by in silico approach. We also reviewed TYR (T373K, N371Y, M370T, and P313R), OCA2 (R305W), TYRP1 (R326H and R356Q) mutations and their structural consequences at molecular level. It is observed that the pathological genetic mutations and their structural and functional significance of OCA genes will aid in development of personalized medicine for albinism patients.
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Affiliation(s)
- Balu Kamaraj
- Bioinformatics Division, School of Bio Sciences and Technology (SBST), Vellore Institute of Technology University, Vellore, Tamil Nadu 632014, India
| | - Rituraj Purohit
- Bioinformatics Division, School of Bio Sciences and Technology (SBST), Vellore Institute of Technology University, Vellore, Tamil Nadu 632014, India
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Wilk MA, McAllister JT, Cooper RF, Dubis AM, Patitucci TN, Summerfelt P, Anderson JL, Stepien KE, Costakos DM, Connor TB, Wirostko WJ, Chiang PW, Dubra A, Curcio CA, Brilliant MH, Summers CG, Carroll J. Relationship between foveal cone specialization and pit morphology in albinism. Invest Ophthalmol Vis Sci 2014; 55:4186-98. [PMID: 24845642 DOI: 10.1167/iovs.13-13217] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism. METHODS We recruited 32 subjects with a clinical diagnosis of albinism. DNA was obtained from 25 subjects, and known albinism genes were analyzed for mutations. Relative inner and outer segment (IS and OS) lengthening (fovea-to-perifovea ratio) was determined from manually segmented spectral domain-optical coherence tomography (SD-OCT) B-scans. Foveal pit morphology was quantified for eight subjects from macular SD-OCT volumes. Ten subjects underwent imaging with adaptive optics scanning light ophthalmoscopy (AOSLO), and cone density was measured. RESULTS We found mutations in 22 of 25 subjects, including five novel mutations. All subjects lacked complete excavation of inner retinal layers at the fovea, though four subjects had foveal pits with normal diameter and/or volume. Peak cone density and OS lengthening were variable and overlapped with that observed in normal controls. A fifth hyper-reflective band was observed in the outer retina on SD-OCT in the majority of the subjects with albinism. CONCLUSIONS Foveal cone specialization and pit morphology vary greatly in albinism. Normal cone packing was observed in the absence of a foveal pit, suggesting a pit is not required for packing to occur. The degree to which retinal anatomy correlates with genotype or visual function remains unclear, and future examination of larger patient groups will provide important insight on this issue.
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Affiliation(s)
- Melissa A Wilk
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - John T McAllister
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Robert F Cooper
- Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States
| | - Adam M Dubis
- Moorfields Eye Hospital, London, United Kingdom Institute of Ophthalmology, University College London, United Kingdom
| | - Teresa N Patitucci
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Phyllis Summerfelt
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | | | - Kimberly E Stepien
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Deborah M Costakos
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Thomas B Connor
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - William J Wirostko
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Pei-Wen Chiang
- Casey Eye Institute Molecular Diagnostics Laboratory, Portland, Oregon, United States
| | - Alfredo Dubra
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Christine A Curcio
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham, Alabama, United States
| | - Murray H Brilliant
- Center for Human Genetics, Marshfield Clinic, Marshfield, Wisconsin, United States
| | - C Gail Summers
- Departments of Ophthalmology and Visual Neurosciences and Pediatrics, University of Minnesota, Minneapolis, Minnesota, United States
| | - Joseph Carroll
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
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Summers CG, Connett JE, Holleschau AM, Anderson JL, De Becker I, McKay BS, Brilliant MH. Does levodopa improve vision in albinism? Results of a randomized, controlled clinical trial. Clin Exp Ophthalmol 2014; 42:713-21. [PMID: 24641678 DOI: 10.1111/ceo.12325] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Accepted: 02/20/2014] [Indexed: 11/26/2022]
Abstract
BACKGROUND Dopamine is an intermediate product in the biosynthesis of melanin pigment, which is absent or reduced in albinism. Animal research has shown that supplying a precursor to dopamine, levodopa, may improve visual acuity in albinism by enhancing neural networks. This study examines the safety and effectiveness of levodopa on best-corrected visual acuity in human subjects with albinism. DESIGN Prospective, randomized, placebo-controlled, double-masked clinical trial conducted at the University of Minnesota. PARTICIPANTS Forty-five subjects with albinism. METHODS Subjects with albinism were randomly assigned to one of three treatment arms: levodopa 0.76 mg/kg with 25% carbidopa, levodopa 0.51 mg/kg with 25% carbidopa, or placebo and followed for 20 weeks, with best-corrected visual acuity measured at enrollment, and at weeks 5, 10, 15, and 20 after enrollment. Side-effects were recorded with a symptom survey. Blood was drawn for genotyping. MAIN OUTCOME MEASURES Side-effects and best-corrected visual acuity 20 weeks after enrolment. RESULTS All subjects had at least one mutation found in a gene known to cause albinism. Mean age was 14.5 years (range: 3.5 to 57.8 years). Follow up was 100% and compliance was good. Minor side-effects were reported; there were no serious adverse events. There was no statistically significant improvement in best-corrected visual acuity after 20 weeks with either dose of levodopa. CONCLUSIONS Levodopa, in the doses used in this trial and for the time course of administration, did not improve visual acuity in subjects with albinism.
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Affiliation(s)
- C Gail Summers
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA; Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota, USA
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Greaves M. Was skin cancer a selective force for black pigmentation in early hominin evolution? Proc Biol Sci 2014; 281:20132955. [PMID: 24573849 PMCID: PMC3953838 DOI: 10.1098/rspb.2013.2955] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 01/23/2014] [Indexed: 02/01/2023] Open
Abstract
Melanin provides a crucial filter for solar UV radiation and its genetically determined variation influences both skin pigmentation and risk of cancer. Genetic evidence suggests that the acquisition of a highly stable melanocortin 1 receptor allele promoting black pigmentation arose around the time of savannah colonization by hominins at some 1-2 Ma. The adaptive significance of dark skin is generally believed to be protection from UV damage but the pathologies that might have had a deleterious impact on survival and/or reproductive fitness, though much debated, are uncertain. Here, I suggest that data on age-associated cancer incidence and lethality in albinos living at low latitudes in both Africa and Central America support the contention that skin cancer could have provided a potent selective force for the emergence of black skin in early hominins.
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Affiliation(s)
- Mel Greaves
- Centre for Evolution and Cancer, Division of Molecular Pathology, Institute of Cancer Research, Brookes Lawley Building, 15 Cotswold Road, Sutton, Surrey SM2 5NG, UK
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30
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Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/498276] [Citation(s) in RCA: 277] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This review presents a general view of all types of melanin in all types of organisms. Melanin is frequently considered just an animal cutaneous pigment and is treated separately from similar fungal or bacterial pigments. Similarities concerning the phenol precursors and common patterns in the formation routes are discussed. All melanins are formed in a first enzymatically-controlled phase, generally a phenolase, and a second phase characterized by an uncontrolled polymerization of the oxidized intermediates. In that second phase, quinones derived from phenol oxidation play a crucial role. Concerning functions, all melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight. In pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host. In turn, some melanins are formed in tissues where sunlight radiation is not a potential threat. Then, their redox, metal chelating, or free radical scavenging properties are more important than light absorption capacity. These pigments sometimes behave as a double-edged sword, and inhibition of melanogenesis is desirable in different cells. Melanin biochemistry is an active field of research from dermatological, biomedical, cosmetical, and microbiological points of view, as well as fruit technology.
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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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32
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Functional characterization of two novel splicing mutations in the OCA2 gene associated with oculocutaneous albinism type II. Gene 2013; 537:79-84. [PMID: 24361966 DOI: 10.1016/j.gene.2013.11.102] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 11/10/2013] [Accepted: 11/27/2013] [Indexed: 02/07/2023]
Abstract
Oculocutaneous albinism (OCA) is characterized by hypopigmentation of the skin, hair and eye, and by ophthalmologic abnormalities caused by a deficiency in melanin biosynthesis. OCA type II (OCA2) is one of the four commonly-recognized forms of albinism, and is determined by mutation in the OCA2 gene. In the present study, we investigated the molecular basis of OCA2 in two siblings and one unrelated patient. The mutational screening of the OCA2 gene identified two hitherto-unknown putative splicing mutations. The first one (c.1503+5G>A), identified in an Italian proband and her affected sibling, lies in the consensus sequence of the donor splice site of OCA2 intron 14 (IVS14+5G>A), in compound heterozygosity with a frameshift mutation, c.1450_1451insCTGCCCTGACA, which is predicted to determine the premature termination of the polypeptide chain (p.I484Tfs*19). In-silico prediction of the effect of the IVS14+5G>A mutation on splicing showed a score reduction for the mutant splice site and indicated the possible activation of a newly-created deep-intronic acceptor splice site. The second mutation is a synonymous transition (c.2139G>A, p.K713K) involving the last nucleotide of exon 20. This mutation was found in a young African albino patient in compound heterozygosity with a previously-reported OCA2 missense mutation (p.T404M). In-silico analysis predicted that the mutant c.2139G>A allele would result in the abolition of the splice donor site. The effects on splicing of these two novel mutations were investigated using an in-vitro hybrid-minigene approach that led to the demonstration of the causal role of the two mutations and to the identification of aberrant transcript variants.
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Morice-Picard F, Lasseaux E, Cailley D, Gros A, Toutain J, Plaisant C, Simon D, François S, Gilbert-Dussardier B, Kaplan J, Rooryck C, Lacombe D, Arveiler B. High-resolution array-CGH in patients with oculocutaneous albinism identifies new deletions of theTYR, OCA2, andSLC45A2genes and a complex rearrangement of theOCA2gene. Pigment Cell Melanoma Res 2013; 27:59-71. [DOI: 10.1111/pcmr.12173] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 09/20/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Fanny Morice-Picard
- Service de Génétique Médicale; CHU de Bordeaux; Bordeaux France
- Maladies Rares: Génétique et Métabolisme (MRGM) EA4576; Univ. Bordeaux; Bordeaux France
| | | | | | - Audrey Gros
- Service de Génétique Médicale; CHU de Bordeaux; Bordeaux France
| | - Jérome Toutain
- Service de Génétique Médicale; CHU de Bordeaux; Bordeaux France
| | | | - Delphine Simon
- Maladies Rares: Génétique et Métabolisme (MRGM) EA4576; Univ. Bordeaux; Bordeaux France
| | - Stéphane François
- Maladies Rares: Génétique et Métabolisme (MRGM) EA4576; Univ. Bordeaux; Bordeaux France
| | | | - Josseline Kaplan
- Laboratoire de Génétique; CHU Paris -Hôpital Necker - Enfants Malades; Paris France
| | - Caroline Rooryck
- Service de Génétique Médicale; CHU de Bordeaux; Bordeaux France
- Maladies Rares: Génétique et Métabolisme (MRGM) EA4576; Univ. Bordeaux; Bordeaux France
| | - Didier Lacombe
- Service de Génétique Médicale; CHU de Bordeaux; Bordeaux France
- Maladies Rares: Génétique et Métabolisme (MRGM) EA4576; Univ. Bordeaux; Bordeaux France
| | - Benoit Arveiler
- Service de Génétique Médicale; CHU de Bordeaux; Bordeaux France
- Maladies Rares: Génétique et Métabolisme (MRGM) EA4576; Univ. Bordeaux; Bordeaux France
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Mártinez-García M, Montoliu L. Albinism in Europe. J Dermatol 2013; 40:319-24. [DOI: 10.1111/1346-8138.12170] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 03/17/2013] [Indexed: 11/27/2022]
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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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Abstract
The progress of molecular genetics helps clinicians to prove or exclude a suspected diagnosis for a vast and yet increasing number of genodermatoses. This leads to precise genetic counselling, prenatal diagnosis and preimplantation genetic haplotyping for many inherited skin conditions. It is also helpful in such occasions as phenocopy, late onset and incomplete penetrance, uniparental disomy, mitochondrial inheritance and pigmentary mosaicism. Molecular methods of two genodermatoses are explained in detail, i.e. genodermatoses with skin fragility and neurofibromatosis type 1.
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Affiliation(s)
- Vesarat Wessagowit
- Molecular Genetics Laboratory, The Institute of Dermatology, Bangkok, Thailand.
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37
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Tuli AM, Valenzuela RK, Kamugisha E, Brilliant MH. Albinism and disease causing pathogens in Tanzania: Are alleles that are associated with OCA2 being maintained by balancing selection? Med Hypotheses 2012; 79:875-8. [DOI: 10.1016/j.mehy.2012.09.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 08/27/2012] [Accepted: 09/20/2012] [Indexed: 10/27/2022]
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Onojafe IF, Adams DR, Simeonov DR, Zhang J, Chan CC, Bernardini IM, Sergeev YV, Dolinska MB, Alur RP, Brilliant MH, Gahl WA, Brooks BP. Nitisinone improves eye and skin pigmentation defects in a mouse model of oculocutaneous albinism. J Clin Invest 2011; 121:3914-23. [PMID: 21968110 DOI: 10.1172/jci59372] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 08/03/2011] [Indexed: 11/17/2022] Open
Abstract
Mutation of the tyrosinase gene (TYR) causes oculocutaneous albinism, type 1 (OCA1), a condition characterized by reduced skin and eye melanin pigmentation and by vision loss. The retinal pigment epithelium influences postnatal visual development. Therefore, increasing ocular pigmentation in patients with OCA1 might enhance visual function. There are 2 forms of OCA1, OCA-1A and OCA-1B. Individuals with the former lack functional tyrosinase and therefore lack melanin, while individuals with the latter produce some melanin. We hypothesized that increasing plasma tyrosine concentrations using nitisinone, an FDA-approved inhibitor of tyrosine degradation, could stabilize tyrosinase and improve pigmentation in individuals with OCA1. Here, we tested this hypothesis in mice homozygous for either the Tyrc-2J null allele or the Tyrc-h allele, which model OCA-1A and OCA-1B, respectively. Only nitisinone-treated Tyrc-h/c-h mice manifested increased pigmentation in their fur and irides and had more pigmented melanosomes. High levels of tyrosine improved the stability and enzymatic function of the Tyrc-h protein and also increased overall melanin levels in melanocytes from a human with OCA-1B. These results suggest that the use of nitisinone in OCA-1B patients could improve their pigmentation and potentially ameliorate vision loss.
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Affiliation(s)
- Ighovie F Onojafe
- Unit on Pediatric, Developmental, and Genetic Eye Disease, National Eye Institute, NIH, Bethesda, Maryland 20892, USA
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High resolution mapping of OCA2 intragenic rearrangements and identification of a founder effect associated with a deletion in Polish albino patients. Hum Genet 2010; 129:199-208. [DOI: 10.1007/s00439-010-0913-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/03/2010] [Indexed: 11/26/2022]
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Carrasco A, Forbes EM, Jeambrun P, Brilliant MH. A splice site mutation is the cause of the high prevalence of oculocutaneous albinism type 2 in the Kuna population. Pigment Cell Melanoma Res 2009; 22:645-7. [PMID: 19397757 DOI: 10.1111/j.1755-148x.2009.00575.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Saadeh R, Lisi EC, Batista DAS, McIntosh I, Hoover-Fong JE. Albinism and developmental delay: the need to test for 15q11-q13 deletion. Pediatr Neurol 2007; 37:299-302. [PMID: 17903679 PMCID: PMC2128718 DOI: 10.1016/j.pediatrneurol.2007.06.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 05/16/2007] [Accepted: 06/20/2007] [Indexed: 11/20/2022]
Abstract
We report on a 17-month-old African girl with cutaneous and ophthalmologic features of oculocutaneous albinism type 2 as well as microcephaly, absent speech, and tremulous movements. Mutations of the P gene within the Angelman/Prader-Willi syndrome critical region at 15q11-q13 cause oculocutaneous albinism type 2. Comorbid oculocutaneous albinism and Angelman syndrome were suspected and confirmed by cytogenetics. Phenotypic features of Angelman syndrome or Prader-Willi syndrome in a patient with albinism should prompt further investigation.
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Affiliation(s)
- Reem Saadeh
- Institute of Genetic Medicine, Johns Hopkins University, Baltimore, Maryland 21287, USA.
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Aquaron R, Soufir N, Bergé-Lefranc JL, Badens C, Austerlitz F, Grandchamp B. Oculocutaneous albinism type 2 (OCA2) with homozygous 2.7-kb deletion of the P gene and sickle cell disease in a Cameroonian family. Identification of a common TAG haplotype in the mutated P gene. J Hum Genet 2007; 52:771-780. [PMID: 17767372 DOI: 10.1007/s10038-007-0181-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Accepted: 07/20/2007] [Indexed: 11/25/2022]
Abstract
In this study, we report on a Cameroonian family from the Ewondo ethnic group, presenting with three oculocutaneous albinism type 2 (OCA2) patients homozygous for the 2.7-kb deletion of the P gene. In one of these patients OCA2 was associated with sickle cell anaemia and in two with the sickle cell trait. We took this opportunity to determine single nucleotide polymorphism (SNP) haplotypes within the P gene in this family in comparison with a group of 53 OCA2 patients homozygous for the same mutation and with a matched unrelated full-coloured control group of 49 subjects, originating from seven different ethnic groups of Southern Cameroon including Ewondo. A combination of five exonic and intronic SNPs in the OCA2 gene was genotyped by sequencing PCR products. We found 3 different haplotypes (TAGCT, TAGTT and TAGCC with frequencies of 0.66, 0.28 and 0.06, respectively) associated with the mutation in the 53 OCA2 patients, while 11 different haplotypes were observed in the control group. These observations suggest that the mutation appeared on the relatively frequent haplotype TAGCT, and that the two other haplotypes are derived from two independent recombination events. These haplotypic data, associated with a value of 1/15,000 for the prevalence of the 2.7-kb mutation, a present effective population size of 10,000,000 for Cameroon and a recombination rate of 0.0031, allowed us to estimate that this mutation originated 4,100-5,645 years ago.
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Affiliation(s)
- Robert Aquaron
- Laboratoire de Biochimie et Biologie Moléculaire, Faculté de Médecine, Université de la Méditerranée Aix-Marseille II, 27 Boulevard Jean Moulin, 13385, Marseille, Cedex 5, France.
| | - Nadem Soufir
- Biochimie hormonale et Génétique, AP-HP, Hôpital Bichat-Claude Bernard, Paris, France
| | | | - Catherine Badens
- Faculté de Médecine, Centre d'Enseignement et de Recherche en Génétique Médicale, Marseille, France
| | - Frederic Austerlitz
- Laboratoire Ecologie, Systématique et Evolution, UMR CNRS/UPS/ENGREF 8079, Université Paris Sud, Orsay, France
| | - Bernard Grandchamp
- Biochimie hormonale et Génétique, AP-HP, Hôpital Bichat-Claude Bernard, Paris, France
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Frudakis T, Terravainen T, Thomas M. Multilocus OCA2 genotypes specify human iris colors. Hum Genet 2007; 122:311-26. [PMID: 17619204 DOI: 10.1007/s00439-007-0401-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Accepted: 06/25/2007] [Indexed: 01/18/2023]
Abstract
Human iris color is a quantitative, multifactorial phenotype that exhibits quasi-Mendelian inheritance. Recent studies have shown that OCA2 polymorphism underlies most of the natural variability in human iris pigmentation but to date, only a few associated polymorphisms in this gene have been described. Herein, we describe an iris color score (C) for quantifying iris melanin content in-silico and undertake a more detailed survey of the OCA2 locus (n = 271 SNPs). In 1,317 subjects, we confirmed six previously described associations and identified another 27 strongly associated with C that were not explained by continental population stratification (OR 1.5-17.9, P = 0.03 to <0.001). Haplotype analysis with respect to these 33 SNPs revealed six haplotype blocks and 11 hap-tags within these blocks. To identify genetic features for best-predicting iris color, we selected sets of SNPs by parsing P values among possible combinations and identified four discontinuous and non-overlapping sets across the LD blocks (p-Selected SNP sets). In a second, partially overlapping sample of 1,072, samples with matching diplotypes comprised of these p-Selected OCA2 SNPs exhibited a rate of C concordance of 96.3% (n = 82), which was significantly greater than that obtained from randomly selected samples (62.6%, n = 246, P<0.0001). In contrast, the rate of C concordance using diplotypes comprised of the 11 identified hap-tags was only 83.7%, and that obtained using diplotypes comprised of all 33 SNPs organized as contiguous sets along the locus (defined by the LD block structure) was only 93.3%. These results confirm that OCA2 is the major human iris color gene and suggest that using an empirical database-driven system, genotypes from a modest number of SNPs within this gene can be used to accurately predict iris melanin content from DNA.
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Affiliation(s)
- Tony Frudakis
- DNAPrint Genomics, Inc, 1621 W. University Pkwy, Sarasota, FL 34243, USA.
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Lund PM. Oculocutaneous albinism in southern Africa: population structure, health and genetic care. Ann Hum Biol 2005; 32:168-73. [PMID: 16096213 DOI: 10.1080/03014460500075423] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND People with oculocutaneous albinism (OCA) have reduced levels of melanin in their hair, skin and eyes, with associated visual impairment and extreme sun sensitivity requiring lifelong monitoring. This genetic condition is surrounded by myth, superstition and fear in Africa, where affected individuals and their families may be rejected, shunned and excluded from their community. OBJECTIVE This review reports population studies in southern Africa to determine the distribution of people with OCA in this predominantly rural and relatively impoverished area-crucial information for health and education providers. Health and genetic care studies document the range of eye and skin problems experienced and suggest effective and sustainable ways to manage these needs in a low resource setting. CONCLUSION Innovative genetic care programmes in northern South Africa facilitate low-cost management of albinism, raise self-esteem and promote community awareness, helping to improve the long-term health prospects and social integration of those affected. This holistic approach of dealing with albinism from both a medical and a sociological perspective could be applied in other areas of Africa where this condition is prevalent.
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Affiliation(s)
- P M Lund
- Cell and Molecular Biosciences, Coventry University, Coventry CV1 5FB, UK.
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Ni-Komatsu L, Orlow SJ. Heterologous expression of tyrosinase recapitulates the misprocessing and mistrafficking in oculocutaneous albinism type 2: effects of altering intracellular pH and pink-eyed dilution gene expression. Exp Eye Res 2005; 82:519-28. [PMID: 16199032 DOI: 10.1016/j.exer.2005.08.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 08/09/2005] [Accepted: 08/11/2005] [Indexed: 11/17/2022]
Abstract
The processing and trafficking of tyrosinase, a melanosomal protein essential for pigmentation, was investigated in a human epithelial 293 cell line that stably expresses the protein. The effects of the pink-eyed dilution (p) gene product, in which mutations result in oculocutaneous albinism type 2 (OCA2), on the processing and trafficking of tyrosinase in this cell line were studied. The majority of tyrosinase was retained in the endoplasmic reticulum-Golgi intermediate compartment and the early Golgi compartment in the 293 cells expressing the protein. Coexpression of p could partially correct the mistrafficking of tyrosinase in 293 cells. Tyrosinase was targeted to the late endosomal and lysosomal compartments after treatment of the cells with compounds that correct the tyrosinase mistrafficking in albino melanocytes, most likely through altering intracellular pH, while the substrate tyrosine had no effect on the processing of tyrosinase. Remarkably, this heterologous expression system recapitulates the defective processing and mistrafficking of tyrosinase observed in OCA2 albino melanocytes and certain amelanotic melanoma cells. Coexpression of other melanosomal proteins in this heterologous system may further aid our understanding of the details of normal and pathologic processing of melanosomal proteins.
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Affiliation(s)
- Li Ni-Komatsu
- The Ronald O. Perelman Department of Dermatology and Cell Biology, New York University School of Medicine, Dermatology Room H-100, NYU School of Medicine, 560 First Avenue, New York, NY 10016, USA
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Schülein R. The early stages of the intracellular transport of membrane proteins: clinical and pharmacological implications. Rev Physiol Biochem Pharmacol 2004; 151:45-91. [PMID: 15103508 DOI: 10.1007/s10254-004-0022-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Intracellular transport mechanisms ensure that integral membrane proteins are delivered to their correct subcellular compartments. Efficient intracellular transport is a prerequisite for the establishment of both cell architecture and function. In the past decade, transport processes of proteins have also drawn the attention of clinicians and pharmacologists since many diseases have been shown to be caused by transport-deficient proteins. Membrane proteins residing within the plasma membrane are transported via the secretory (exocytotic) pathway. The general transport routes of the secretory pathway are well established. The transport of membrane proteins starts with their integration into the ER membrane. The ribosomes synthesizing membrane proteins are targeted to the ER membrane, and the nascent chains are co-translationally integrated into the bilayer, i.e., they are inserted while their synthesis is in progress. During ER insertion, the orientation (topology) of the proteins in the membrane is determined. Proteins are folded, and their folding state is checked by a quality control system that allows only correctly folded forms to leave the ER. Misfolded or incompletely folded forms are retained, transported back to the cytosol and finally subjected to proteolysis. Correctly folded proteins are transported in the membranes of vesicles through the ER/Golgi intermediate compartment (ERGIC) and the individual compartments of the Golgi apparatus ( cis, medial, trans) to the plasma membrane. In this review, the current knowledge of the first stages of the intracellular trafficking of membrane proteins will be summarized. This "early secretory pathway" includes the processes of ER insertion, topology determination, folding, quality control and the transport to the Golgi apparatus. Mutations in the genes of membrane proteins frequently lead to misfolded forms that are recognized and retained by the quality control system. Such mutations may cause inherited diseases like cystic fibrosis or retinitis pigmentosa. In the second part of this review, the clinical implications of the early secretory pathway will be discussed. Finally, new pharmacological strategies to rescue misfolded and transport-defective membrane proteins will be outlined.
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Affiliation(s)
- R Schülein
- Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Rössle-Str. 10, 13125 Berlin, Germany.
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Cohen-Barak O, Yi Z, Hagiwara N, Monzen K, Komuro I, Brilliant MH. Sox6 regulation of cardiac myocyte development. Nucleic Acids Res 2004; 31:5941-8. [PMID: 14530442 PMCID: PMC219484 DOI: 10.1093/nar/gkg807] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A mouse mutation (p100H/p100H) has been identified that is associated with cardioskeletal myopathy, heart block, delayed growth and early postnatal death. The gene that is disrupted in this mutation encodes the transcription factor Sox6. P19CL6 cells were used as an in vitro cardiomyocyte differentiation system and revealed that Sox6 is expressed exclusively when the cells are committed to differentiate to beating cardiac myocytes. We used the yeast two-hybrid system to identify the Prtb (Proline-rich transcript of the brain) protein as a Sox6 interactor, and subsequently confirmed the interaction by co-immunoprecipitation. Prtb expression in P19CL6 cells increased with differentiation to beating cardiomyocytes. Using the P19CL6 cells stably transfected with noggin, an antagonist of BMP (Bone Morphogenic Protein), we found that BMP expression is required for Sox6 expression in cardiomyocyte differentiation. Surprisingly, the expression of the alpha1c-subunit gene of the L-type Ca2+ channel decreased in P19CL6 cells as they differentiated to beating cardiac cells. Ectopic expression of Sox6 or Prtb alone in P19CL6 cells caused down-regulation of L-type Ca2+ alpha1c expression, but when Sox6 and Prtb were co-transfected to the cells, L-type Ca2+ alpha1c remained at basal levels. A similar relationship of Sox6 and L-type Ca2+ alpha1c expression was seen in vivo (comparing wild-type and p(100H)/p(100H) mutant mice). Thus, Sox6 is within the BMP pathway in cardiac differentiation, interacts with Prtb and may play a critical role in the regulation of a cardiac L-type Ca2+ channel.
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Affiliation(s)
- Orit Cohen-Barak
- Department of Pediatrics, The University of Arizona College of Medicine, Steele Memorial Children's Research Center 1501 N. Campbell Avenue, Tucson, AZ 85724, USA
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Frudakis T, Thomas M, Gaskin Z, Venkateswarlu K, Chandra KS, Ginjupalli S, Gunturi S, Natrajan S, Ponnuswamy VK, Ponnuswamy KN. Sequences Associated With Human Iris Pigmentation. Genetics 2003; 165:2071-83. [PMID: 14704187 PMCID: PMC1462887 DOI: 10.1093/genetics/165.4.2071] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
To determine whether and how common polymorphisms are associated with natural distributions of iris colors, we surveyed 851 individuals of mainly European descent at 335 SNP loci in 13 pigmentation genes and 419 other SNPs distributed throughout the genome and known or thought to be informative for certain elements of population structure. We identified numerous SNPs, haplotypes, and diplotypes (diploid pairs of haplotypes) within the OCA2, MYO5A, TYRP1, AIM, DCT, and TYR genes and the CYP1A2-15q22-ter, CYP1B1-2p21, CYP2C8-10q23, CYP2C9-10q24, and MAOA-Xp11.4 regions as significantly associated with iris colors. Half of the associated SNPs were located on chromosome 15, which corresponds with results that others have previously obtained from linkage analysis. We identified 5 additional genes (ASIP, MC1R, POMC, and SILV) and one additional region (GSTT2-22q11.23) with haplotype and/or diplotypes, but not individual SNP alleles associated with iris colors. For most of the genes, multilocus gene-wise genotype sequences were more strongly associated with iris colors than were haplotypes or SNP alleles. Diplotypes for these genes explain 15% of iris color variation. Apart from representing the first comprehensive candidate gene study for variable iris pigmentation and constituting a first step toward developing a classification model for the inference of iris color from DNA, our results suggest that cryptic population structure might serve as a leverage tool for complex trait gene mapping if genomes are screened with the appropriate ancestry informative markers.
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Abstract
Pigmentary disorders are commonly seen in ethnic skin. They are psychologically problematic in darker skin. Treatment of many of these disorders remains difficult.
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Affiliation(s)
- Rebat M Halder
- Department of Dermatology, Howard University College of Medicine, 2041 Georgia Avenue, NW, Washington, DC 20060, USA
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