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Dolinska MB, Kus NJ, Farney SK, Wingfield PT, Brooks BP, Sergeev YV. Oculocutaneous albinism type 1: link between mutations, tyrosinase conformational stability, and enzymatic activity. Pigment Cell Melanoma Res 2017; 30:41-52. [PMID: 27775880 DOI: 10.1111/pcmr.12546] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 10/13/2016] [Indexed: 12/19/2022]
Abstract
Oculocutaneous albinism type 1 (OCA1) is an autosomal recessive disorder caused by mutations in the tyrosinase gene. Two subtypes of OCA1 have been described: severe OCA1A with complete absence of tyrosinase activity and less severe OCA1B with residual tyrosinase activity. Here, we characterize the recombinant human tyrosinase intramelanosomal domain and mutant variants, which mimic genetic changes in both subtypes of OCA1 patients. Proteins were prepared using site-directed mutagenesis, expressed in insect larvae, purified by chromatography, and characterized by enzymatic activities, tryptophan fluorescence, and Gibbs free energy changes. The OCA1A mutants showed very low protein expression and protein yield and are enzymatically inactive. Mutants mimicking OCA1B were biochemically similar to the wild type, but exhibited lower specific activities and protein stabilities. The results are consistent with clinical data, which indicates that OCA1A mutations inactivate tyrosinase and result in severe phenotype, while OCA1B mutations partially inactivate tyrosinase and result in OCA1B albinism.
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Affiliation(s)
- Monika B Dolinska
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Nicole J Kus
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - S Katie Farney
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Paul T Wingfield
- National Institute of Artritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Brian P Brooks
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Yuri V Sergeev
- National Eye Institute, National Institutes of Health, Bethesda, MD, USA
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Kono M, Kondo T, Ito S, Suzuki T, Wakamatsu K, Ito S, Tomita Y. Genotype analysis in a patient with oculocutaneous albinism 1 minimal pigment type. Br J Dermatol 2012; 166:896-8. [DOI: 10.1111/j.1365-2133.2011.10690.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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King RA, Oetting WS. Molecular basis of type IA (tyrosinase negative) oculocutaneous albinism. PIGMENT CELL RESEARCH 2008; Suppl 2:249-53. [PMID: 1409426 DOI: 10.1111/j.1600-0749.1990.tb00380.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Type IA (Tyrosinase negative) oculocutaneous albinism (OCA) is produced by mutations of the tyrosinase gene. We have found a total of 13 different mutations associated with type IA OCA. Analysis of the distribution of the 9 missense mutations shows that most of these mutations cluster in three areas of the gene. All but one of these mutations involve amino acids that are conserved between the mouse and human. Two clusters involve the copper A and copper B binding sites, and could disrupt the metal ion-protein interaction necessary for enzyme function. The third cluster is in exon I and could represent an important functional domain of the enzyme such as the tyrosine binding site. The deletion or insertion frameshift mutations are distributed throughout the coding region and do not appear to cluster. We conclude that a diverse number of mutations are responsible for type IA OCA and many individuals are compound heterozygotes for mutations responsible for this genetic disease (Table 3).
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Affiliation(s)
- R A King
- Department of Medicine, University of Minnesota, Minneapolis 55455
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Du J, Fisher DE. Identification of Aim-1 as the underwhite mouse mutant and its transcriptional regulation by MITF. J Biol Chem 2002; 277:402-6. [PMID: 11700328 DOI: 10.1074/jbc.m110229200] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Animal pigmentation mutants have provided rich models for the identification of genes modulating pathways from melanocyte development to melanoma. One mouse model is the underwhite locus, alleles of which manifest altered pigmentation of both eye and fur, sometimes in an age-dependent fashion. Here we show that the mouse homolog of a recently identified gene whose mutation produces Japanese gold-colored fish, medaka b, maps to the mouse underwhite locus. We identify distinct mutations of this gene, known as Aim-1, in three underwhite mouse alleles and find that structure/function differences correlate with recessive versus dominant inheritance. The human ortholog of AIM-1 was originally identified as a melanocyte-restricted antigen that is recognized by autologous T cells from a patient with melanoma. We also provide evidence that AIM-1 is transcriptionally modulated by MITF, a melanocyte-specific transcription factor essential to pigmentation and a clinical diagnostic marker in human melanoma. Although AIM-1 appears to reside downstream of MITF, chromatin immunoprecipitations do not reveal binding of MITF to a 5'-flanking region containing histone 3 acetylation, indicating that MITF either acts indirectly on AIM-1 or it binds to a remote regulatory sequence. Nevertheless, MITF links AIM-1 expression and the underwhite phenotype to a transcriptional network central to pigmentation in mammals.
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Affiliation(s)
- Jinyan Du
- Division of Pediatric Hematology/Oncology, Children's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
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Abstract
Oculocutaneous albinism (OCA) is a complex group of genetic disorders that have historically been defined by clinical and biochemical methods. Recent advances in the molecular biology of pigmentation have greatly increased our understanding of the complexity of this group of disorders. To date, two different types of OCA (OCA1 and OCA2) have been mapped to specific chromosomal regions. Mutations have been found in the tyrosinase locus associated with OCA1 and the human homologue to the murine pink-eyed dilution locus associated with OCA2. Analysis of these genes and their mutations will allow us to better define and categorize the different types of albinism. Further, the analysis of these genes and their mutations will provide information on the role of these gene products in melanin biosynthesis and the effect specific mutations have on the pathogenesis of albinism.
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Affiliation(s)
- W S Oetting
- Department of Medicine, University of Minnesota, Minneapolis 55455
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Abstract
PURPOSE The purpose of this study is to describe the heterogeneous phenotype of individuals with an unusual type of albinism--minimal pigment oculocutaneous albinism. METHODS Nine patients with minimal pigment oculocutaneous albinism were identified and followed for up to 11 years. The criteria were the presence of oculocutaneous albinism in association with low hairbulb tyrosinase activity in the patient and disparate activity in the parents with one parent having normal activity and the other having low tyrosinase activity. Changes in skin, hair, and ocular pigment were followed as the patients matured. As a measure of ocular pigment, iris transillumination and macular transparency were graded according to a previously published scheme. RESULTS Patients were born with white scalp hair and skin, and nystagmus developed. Visual acuity was reduced to 20/50 to 20/200 for the group, but in one patient vision improved with maturity. Irides were blue. In seven patients, iris pigment developed, which was detected by transillumination with slit-lamp biomicroscopy, including the one patient with improved visual acuity. All patients had foveal hypoplasia, and melanin pigment in the fundi could not be detected by clinical examination. Visual acuity in the group did not correlate directly with the presence or development of iris transillumination or macular transparency. The pedigrees were consistent with an autosomal recessive inheritance pattern. CONCLUSION This unique type of oculocutaneous albinism has heterogeneous clinical features. Minimal pigment oculocutaneous albinism appears to represent a new type of tyrosinase-related oculocutaneous albinism (OCA1MP).
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Affiliation(s)
- C G Summers
- Department of Ophthalmology, University of Minnesota, Minneapolis
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Oetting WS, Fryer JP, Oofuji Y, Middendorf LR, Brumbaugh JA, Summers CG, King RA. Analysis of tyrosinase gene mutations using direct automated infrared fluorescence DNA sequencing of amplified exons. Electrophoresis 1994; 15:159-64. [PMID: 8026428 DOI: 10.1002/elps.1150150127] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The ability to correctly diagnose the molecular cause of genetic diseases is becoming increasingly important in medicine. This requires an efficient method for the analysis of the DNA sequence of specific genes and the detection of mutations in affected individuals. We report a method to determine the mutations responsible for tyrosinase related albinism (OCA1) using a combination of polymerase chain reaction-single stranded conformational polymorphism (PCR-SSCP) analysis and direct DNA cycle sequencing using fluorescently labeled oligonucleotides and an automated DNA sequencer based on infrared fluorescence technology. This method allows DNA from several individuals to be sequenced quickly and simultaneously so that the specific location of each mutation and the carrier status of family members can be determined.
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Affiliation(s)
- W S Oetting
- Department of Medicine, University of Minnesota, Minneapolis 55455
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Oetting WS, King RA. Molecular basis of type I (tyrosinase-related) oculocutaneous albinism: mutations and polymorphisms of the human tyrosinase gene. Hum Mutat 1993; 2:1-6. [PMID: 8477259 DOI: 10.1002/humu.1380020102] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Type I (tyrosinase related) oculocutaneous albinism (OCA) results from mutations of the tyrosinase gene on chromosome 11q that lead to reduced or absent melanin pigment synthesis. The phenotype of Type I OCA is broad, ranging from a total lack to only a moderate reduction of melanin, and the phenotypic variation is associated with different mutant alleles at the tyrosinase locus. A total of 36 mutations have been identified in Type I OCA including 24 missense, 4 nonsense, and 8 frameshift mutations. The majority of affected individuals have been compound heterozygotes with different maternal and paternal alleles. Six polymorphic sites for haplotype analysis have been identified in the tyrosinase gene including 2 in the promoter region, 2 in the coding region associated with alternative amino acids in the protein, and 2 RFLPs in the first intron.
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Affiliation(s)
- W S Oetting
- Department of Medicine, University of Minnesota, Minneapolis 55455
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Oetting WS, Handoko HY, Mentink MM, Paller AS, White JG, King RA. Molecular analysis of an extended family with type IA (tyrosinase-negative) oculocutaneous albinism. J Invest Dermatol 1991; 97:15-9. [PMID: 1676041 DOI: 10.1111/1523-1747.ep12477808] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We have analyzed the tyrosinase coding region of three individuals having Type IA OCA within an extended family using genomic DNA amplification and dideoxy sequencing. Two of the affected individuals are dizygotic twins. All three have a common missense mutation at codon 81 (Pro----Leu) within exon I. The twins have a second missense mutation at codon 371 (Asn----Thr) within exon III and the third individual has a second missense mutation at codon 47 (Gly----Asp) within exon I. For each of these three individuals, the loss of enzyme function is the result of two different mutations, showing that they are compound heterozygotes of two mutant tyrosinase alleles.
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Affiliation(s)
- W S Oetting
- Department of Medicine, University of Minnesota, Minneapolis 55455
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Castronuovo S, Simon JW, Kandel GL, Morier A, Wolf B, Witkop CJ, Jenkins PL. Variable expression of albinism within a single kindred. Am J Ophthalmol 1991; 111:419-26. [PMID: 1901453 DOI: 10.1016/s0002-9394(14)72374-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We studied the albinotic characteristics in 13 members of a white family (age range, 2 to 73 years), which were graded according to severity and were correlated with visual acuity. Clinical, electrophysiologic, and biochemical characteristics of this family do not fit any known category of human albinism. The degree of heterogeneity in expression of albinotic features was unexpected. The correlation between visual acuity and nystagmus was particularly strong. The brown-haired propositus had severe skin involvement, iris transillumination, fundus hypopigmentation, and foveal hypoplasia. He had no manifest nystagmus, however, and his visual acuity was nearly normal. These observations suggest that nystagmus imposes a visual deficit beyond that related to foveal hypoplasia alone.
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Affiliation(s)
- S Castronuovo
- Department of Ophthalmology, Albany Medical College, New York 12208
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King RA, Townsend D, Oetting W, Summers CG, Olds DP, White JG, Spritz RA. Temperature-sensitive tyrosinase associated with peripheral pigmentation in oculocutaneous albinism. J Clin Invest 1991; 87:1046-53. [PMID: 1900307 PMCID: PMC329899 DOI: 10.1172/jci115064] [Citation(s) in RCA: 63] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Several types of autosomal recessive oculocutaneous albinism (OCA) are associated with abnormal tyrosinase function and a generalized reduction in or absence of cutaneous and eye melanin. Each is thought to result from a different mutant allele at the tyrosinase locus, with the mutation producing an enzyme with little or no activity in all involved tissues. In this paper, we report a new type of OCA that results from a tyrosinase allele producing a temperature-sensitive enzyme. The proband had white hair in the warmer areas (scalp and axilla) and progressively darker hair in the cooler areas (extremities) of her body. Melanocyte and melanosome architecture were normal. Quantitative hairbulb tyrosinase (dopa oxidase) assay demonstrated a loss of activity above 35-37 degrees C. Plasma pheomelanin and urine eumelanin intermediates were reduced and correlated with hair melanin content. This is the first temperature-sensitive tyrosinase mutation to be reported in humans and is analogous to the Siamese mutation in the cat and the Himalayan mutation in the mouse.
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Affiliation(s)
- R A King
- Department of Medicine, University of Minnesota, Minneapolis 55455
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Keeffe JE. Assessment and educational implications of albinism. OPHTHALMIC PAEDIATRICS AND GENETICS 1990; 11:215-24. [PMID: 2280980 DOI: 10.3109/13816819009020982] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Forty-seven visually impaired albino schoolchildren were identified from the Victorian school population. 28 (aged 7-18) who had had a standard ophthalmic examination including the LH5 Visual Acuity Test for Contrast Sensitivity agreed to try a battery of educational tests in addition. The tests were the Non-Verbal Ability Test, Visual Motor Integration Test, Torch Reading, reading miscue analysis and reading of test to measure sustained near visual acuity. The most useful of these was the Non-Verbal Ability Test (NAT) which indicated that this group of albinos was of above average cognitive ability. This was independent of the findings on ophthalmic examination. The NAT is also useful in identifying relative strengths and weaknesses in information processing abilities in albino subjects.
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Affiliation(s)
- J E Keeffe
- Department of Ophthalmology, University of Melbourne, Royal Victorian Eye and Ear Hospital, Australia
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