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Le L, Sirés-Campos J, Raposo G, Delevoye C, Marks MS. Melanosome Biogenesis in the Pigmentation of Mammalian Skin. Integr Comp Biol 2021; 61:1517-1545. [PMID: 34021746 PMCID: PMC8516112 DOI: 10.1093/icb/icab078] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Melanins, the main pigments of the skin and hair in mammals, are synthesized within membrane-bound organelles of melanocytes called melanosomes. Melanosome structure and function are determined by a cohort of resident transmembrane proteins, many of which are expressed only in pigment cells and localize specifically to melanosomes. Defects in the genes that encode melanosome-specific proteins or components of the machinery required for their transport in and out of melanosomes underlie various forms of ocular or oculocutaneous albinism, characterized by hypopigmentation of the hair, skin, and eyes and by visual impairment. We review major components of melanosomes, including the enzymes that catalyze steps in melanin synthesis from tyrosine precursors, solute transporters that allow these enzymes to function, and structural proteins that underlie melanosome shape and melanin deposition. We then review the molecular mechanisms by which these components are biosynthetically delivered to newly forming melanosomes-many of which are shared by other cell types that generate cell type-specific lysosome-related organelles. We also highlight unanswered questions that need to be addressed by future investigation.
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Affiliation(s)
- Linh Le
- Department of Pathology & Laboratory Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Cell and Molecular Biology Graduate Group, University of Pennsylvania, Philadelphia, PA, USA
| | - Julia Sirés-Campos
- Institut Curie, PSL Research University, CNRS, UMR 144, Structure and Membrane Compartments, Paris, 75005, France
| | - Graça Raposo
- Institut Curie, PSL Research University, CNRS, UMR 144, Structure and Membrane Compartments, Paris, 75005, France
| | - Cédric Delevoye
- Institut Curie, PSL Research University, CNRS, UMR 144, Structure and Membrane Compartments, Paris, 75005, France
| | - Michael S Marks
- Department of Pathology & Laboratory Medicine, Children’s Hospital of Philadelphia, Philadelphia, PA, USA
- Department of Pathology & Laboratory Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
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2
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Mahmood MS, Irshad S, Butt TA, Batool H, Batool S, Ashraf NM. In-silico analysis of deleterious missense SNPs of human TYR gene associated with oculocutaneous albinism type 1 (OCA1). Meta Gene 2020. [DOI: 10.1016/j.mgene.2020.100674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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3
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Wang GL, Li XQ, Cao GX, Yuan F, Dong Y, Li Z. A novel photoswitchable enzyme cascade for powerful signal amplification in versatile bioassays. Chem Commun (Camb) 2018; 53:11165-11168. [PMID: 28951901 DOI: 10.1039/c7cc05771g] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
This report outlines the construction of an advanced, exquisite photoswitchable enzyme cascade on the basis that tyrosinase (TYR) catalyzes the generation of dihydroxyphenylalanine (DOPA) coordinated TiO2 nanoparticles (NPs) to form a light responsive nano-trigger that subsequently photoactivates the enzymatic activity of horseradish peroxidase (HRP). This photoswitchable enzyme cascade has a powerful signal transduction/amplification ability in TYR-based bioassays, and holds great promise to be applied in versatile applications.
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Affiliation(s)
- Guang-Li Wang
- The Key Laboratory of Synthetic Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, China.
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4
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Abstract
Context: Albinism is an inherited disorder of hypopigmentation involving the skin, eyes, and hair. This disorder results in the absence or reduction in melanin production. There are two main types of albinism which are ocular albinism and oculocutaneous albinism. It could also be classified as syndromic or nonsyndromic the melanin, which protects from the harmful effect of ultraviolet radiation of the sun on the normal skin, is deficient in the albino, predisposing them more, to cutaneous malignancies. Aim: This study is to highlight the epidemiology of cutaneous cancers in albinos in sub-urban Nigeria. Methodology: This is a retrospective review of all albinos with histological diagnoses of cutaneous malignancies that presented to Irrua Specialist Teaching Hospital, Irrua Edo State, Nigeria between September 2010 and August 2016. The following details were extracted from the patients’ case-notes, operation register, and the histopathology register. These data include age, gender, site of the lesion, the diagnosis, no of lesions excised, and duration of the lesion (s). These were collated and analyzed using SPSS version 22. Results: There were 22 albinos with histopathologically diagnosed cutaneous malignancies. There were 11 males and 11 females with male:female of 1. The age range is from 25 to 55 years with the mean of 34.68. Conclusion: Albinism is one of the most common causes of cutaneous malignancies, and majority of them present with locally advanced lesions that will need excision biopsy resulting in disfigurement. This problem can be prevented in many cases with proper community education, support, and free health care. There is also need for them to present early whenever they noticed any skin changes.
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Affiliation(s)
- Oluwafemi Olasupo Awe
- Department of Surgery, Plastic Surgery Unit, Faculty of Clinical Sciences, Ambrose Alli University, Ekpoma, Nigeria.,Department of Surgery, Irrua Specialist Teaching Hospital, Irrua, Edo State, Nigeria
| | - Terence Akhator Azeke
- Department of Morbid Anatomy and Histopathology, Irrua Specialist Teaching Hospital, Irrua, Edo State, Nigeria
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5
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Sharifzadeh G, Hosseinkhani H. Biomolecule-Responsive Hydrogels in Medicine. Adv Healthc Mater 2017; 6. [PMID: 29057617 DOI: 10.1002/adhm.201700801] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Revised: 08/17/2017] [Indexed: 12/19/2022]
Abstract
Recent advances and applications of biomolecule-responsive hydrogels, namely, glucose-responsive hydrogels, protein-responsive hydrogels, and nucleic-acid-responsive hydrogels are highlighted. However, achieving the ultimate purpose of using biomolecule-responsive hydrogels in preclinical and clinical areas is still at the very early stage and calls for more novel designing concepts and advance ideas. On the way toward the real/clinical application of biomolecule-responsive hydrogels, plenty of factors should be extensively studied and examined under both in vitro and in vivo conditions. For example, biocompatibility, biointegration, and toxicity of biomolecule-responsive hydrogels should be carefully evaluated. From the living body's point of view, biocompatibility is seriously depended on the interactions at the tissue/polymer interface. These interactions are influenced by physical nature, chemical structure, surface properties, and degradation of the materials. In addition, the developments of advanced hydrogels with tunable biological and mechanical properties which cause no/low side effects are of great importance.
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Affiliation(s)
- Ghorbanali Sharifzadeh
- Department of Polymer Engineering; Faculty of Chemical Engineering; Universiti Teknologi Malaysia; 81310 Johor Malaysia
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6
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Galante Rocha de Vasconcelos FT, Hauzman E, Dutra Henriques L, Kilpp Goulart PR, de Faria Galvão O, Sano RY, da Silva Souza G, Lynch Alfaro J, de Lima Silveira LC, Fix Ventura D, Oliveira Bonci DM. A novel nonsense mutation in the tyrosinase gene is related to the albinism in a capuchin monkey (Sapajus apella). BMC Genet 2017; 18:39. [PMID: 28476152 PMCID: PMC5420114 DOI: 10.1186/s12863-017-0504-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Accepted: 04/12/2017] [Indexed: 11/27/2022] Open
Abstract
Background Oculocutaneous Albinism (OCA) is an autosomal recessive inherited condition that affects the pigmentation of eyes, hair and skin. The OCA phenotype may be caused by mutations in the tyrosinase gene (TYR), which expresses the tyrosinase enzyme and has an important role in the synthesis of melanin pigment. The aim of this study was to identify the genetic mutation responsible for the albinism in a captive capuchin monkey, and to describe the TYR gene of normal phenotype individuals. In addition, we identified the subject’s species. Results A homozygous nonsense mutation was identified in exon 1 of the TYR gene, with the substitution of a cytosine for a thymine nucleotide (C64T) at codon 22, leading to a premature stop codon (R22X) in the albino robust capuchin monkey. The albino and five non-albino robust capuchin monkeys were identified as Sapajus apella, based on phylogenetic analyses, pelage pattern and geographic provenance. One individual was identified as S. macrocephalus. Conclusion We conclude that the point mutation C64T in the TYR gene is responsible for the OCA1 albino phenotype in the capuchin monkey, classified as Sapajus apella. Electronic supplementary material The online version of this article (doi:10.1186/s12863-017-0504-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Felipe Tadeu Galante Rocha de Vasconcelos
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030
| | - Einat Hauzman
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030.,Instituto Israelita de Ensino e Pesquisa Albert Einstein, Hospital Israelita Albert Einstein, São Paulo, São Paulo, Brazil
| | - Leonardo Dutra Henriques
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030
| | - Paulo Roney Kilpp Goulart
- Núcleo de Teoria e Pesquisa do Comportamento, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110
| | - Olavo de Faria Galvão
- Núcleo de Teoria e Pesquisa do Comportamento, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110
| | - Ronaldo Yuiti Sano
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030.,Departamento de Oftalmologia, Santa Casa de Misericórdia de São Paulo, São Paulo, São Paulo, Brazil
| | - Givago da Silva Souza
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110.,Núcleo de Medicina Tropical, Universidade Federal do Pará, Belém, Pará, Brazil
| | - Jessica Lynch Alfaro
- Institute for Society and Genetics, University of California Los Angeles, Box 957221, 3360 LSB, Los Angeles, CA, USA, 90095-7221.,Department of Anthropology, University of California Los Angeles, Los Angeles, CA, USA
| | - Luis Carlos de Lima Silveira
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110.,Núcleo de Medicina Tropical, Universidade Federal do Pará, Belém, Pará, Brazil
| | - Dora Fix Ventura
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030.,Instituto Israelita de Ensino e Pesquisa Albert Einstein, Hospital Israelita Albert Einstein, São Paulo, São Paulo, Brazil
| | - Daniela Maria Oliveira Bonci
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030. .,Instituto Israelita de Ensino e Pesquisa Albert Einstein, Hospital Israelita Albert Einstein, São Paulo, São Paulo, Brazil.
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7
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Wang J, Lee TS, Zhang Z, Tung CH. A Bioluminogenic Probe for Monitoring Tyrosinase Activity. Chem Asian J 2017; 12:397-400. [PMID: 28052521 DOI: 10.1002/asia.201601659] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 12/29/2016] [Indexed: 11/10/2022]
Abstract
A bioluminogenic probe based on luciferin was designed and synthesized to monitor tyrosinase activity. This probe was efficient in assessing tyrosinase activity in a buffered aqueous solution and in measuring endogenous tyrosinase activity in melanoma cells.
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Affiliation(s)
- Jianguang Wang
- Molecular Imaging Innovations Institute, Department of Radiology, Weill Cornell Medicine, 413 East 69th Street, New York, NY, 10065, USA.,Current address: School of Chemical and Environmental Engineering, Anyang Institute of Technology, West of HuangHe Road, Anyang, 455000, PR China
| | - Tae Sup Lee
- Molecular Imaging Innovations Institute, Department of Radiology, Weill Cornell Medicine, 413 East 69th Street, New York, NY, 10065, USA.,Current address: Division of RI-Convergence Research, Korea Institute of Radiological and Medical Sciences, 75 Nowon-ro, Nowon-gu, Seoul, 01812, Republic of Korea
| | - Zhe Zhang
- Molecular Imaging Innovations Institute, Department of Radiology, Weill Cornell Medicine, 413 East 69th Street, New York, NY, 10065, USA
| | - Ching-Hsuan Tung
- Molecular Imaging Innovations Institute, Department of Radiology, Weill Cornell Medicine, 413 East 69th Street, New York, NY, 10065, USA
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8
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Yan X, Li H, Zheng W, Su X. Visual and Fluorescent Detection of Tyrosinase Activity by Using a Dual-Emission Ratiometric Fluorescence Probe. Anal Chem 2015; 87:8904-9. [DOI: 10.1021/acs.analchem.5b02037] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Xu Yan
- Department
of Analytical Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P.R. China
| | - Hongxia Li
- School
of Pharmacy, Jilin University, Changchun 130021, P.R. China
| | - Weishi Zheng
- State
Key Laboratory of Supramolecular Structure and Materials, College
of Chemistry, Jilin University, Changchun 130012, P.R. China
| | - Xingguang Su
- Department
of Analytical Chemistry, College of Chemistry, Jilin University, Changchun, 130012, P.R. China
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9
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K B, Purohit R. Mutational analysis of TYR gene and its structural consequences in OCA1A. Gene 2013; 513:184-95. [DOI: 10.1016/j.gene.2012.09.128] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Revised: 09/01/2012] [Accepted: 09/23/2012] [Indexed: 01/19/2023]
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10
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11
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Kim TI, Park J, Park S, Choi Y, Kim Y. Visualization of tyrosinase activity in melanoma cells by a BODIPY-based fluorescent probe. Chem Commun (Camb) 2011; 47:12640-2. [DOI: 10.1039/c1cc15061h] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Binesh F, Akhavan A, Navabii H. Nevoid malignant melanoma in an albino woman. BMJ Case Rep 2010; 2010:2010/dec03_1/bcr0820103262. [PMID: 22802236 DOI: 10.1136/bcr.08.2010.3262] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Albinism is a disorder of hypopigmentation affecting the skin, hair and eyes. Ultraviolet light induced cutaneous tumours are common in patients with albinism due to reduced or absent protection from melanin, with squamous cell carcinoma being the most common. Although non-melanomatous skin cancers are more frequent in patients with albinism, dysplastic nevi and melanoma present a greater diagnostic challenge in this group because of their hypopigmented appearance. Here the authors report a case of nevoid malignant melanoma in a patient who had type 1A oculocutaneous albinism.
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Affiliation(s)
- F Binesh
- Department of Pathology, Shahid Sadoghi Hospital, Yazd Shahid Sadoghi University, Yazd, Iran
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13
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Rymer J, Choh V, Bharadwaj S, Padmanabhan V, Modilevsky L, Jovanovich E, Yeh B, Zhang Z, Guan H, Payne W, Wildsoet CF. The albino chick as a model for studying ocular developmental anomalies, including refractive errors, associated with albinism. Exp Eye Res 2007; 85:431-42. [PMID: 17651735 PMCID: PMC2072995 DOI: 10.1016/j.exer.2007.06.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2006] [Revised: 06/06/2007] [Accepted: 06/12/2007] [Indexed: 11/22/2022]
Abstract
Albinism is associated with a variety of ocular anomalies including refractive errors. The purpose of this study was to investigate the ocular development of an albino chick line. The ocular development of both albino and normally pigmented chicks was monitored using retinoscopy to measure refractive errors and high frequency A-scan ultrasonography to measure axial ocular dimensions. Functional tests included an optokinetic nystagmus paradigm to assess visual acuity, and flash ERGs to assess retinal function. The underlying genetic abnormality was characterized using a gene microarray, PCR and a tyrosinase assay. The ultrastructure of the retinal pigment epithelium (RPE) was examined using transmission electron microscopy. PCR confirmed that the genetic abnormality in this line is a deletion in exon 1 of the tyrosinase gene. Tyrosinase gene expression in isolated RPE cells was minimally detectable, and there was minimal enzyme activity in albino feather bulbs. The albino chicks had pink eyes and their eyes transilluminated, reflecting the lack of melanin in all ocular tissues. All three main components, anterior chamber, crystalline lens and vitreous chamber, showed axial expansion over time in both normal and albino animals, but the anterior chambers of albino chicks were consistently shallower than those of normal chicks, while in contrast, their vitreous chambers were longer. Albino chicks remained relatively myopic, with higher astigmatism than the normally pigmented chicks, even though both groups underwent developmental emmetropization. Albino chicks had reduced visual acuity yet the ERG a- and b-wave components had larger amplitudes and shorter than normal implicit times. Developmental emmetropization occurs in the albino chick but is impaired, likely because of functional abnormalities in the RPE and/or retina as well as optical factors. In very young chicks the underlying genetic mutation may also contribute to refractive error and eye shape abnormalities.
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Affiliation(s)
- Jodi Rymer
- Wildsoet Lab, 588 Minor Hall, University of California-Berkeley, Berkeley CA 94720-2020, USA.
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14
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Rooryck C, Morice F, Mortemousque B, Lacombe D, Taïeb A, Arveiler B. Albinisme oculo-cutané. Ann Dermatol Venereol 2007. [DOI: 10.1016/s0151-9638(07)89250-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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15
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Regales L, Giraldo P, García-Díaz A, Lavado A, Montoliu L. Identification and functional validation of a 5' upstream regulatory sequence in the human tyrosinase gene homologous to the locus control region of the mouse tyrosinase gene. ACTA ACUST UNITED AC 2004; 16:685-92. [PMID: 14629727 DOI: 10.1046/j.1600-0749.2003.00100.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Comparison analysis of the sequences of the mouse and human genomes has proven a powerful approach in identifying functional regulatory elements within the non-coding regions that are conserved through evolution between homologous mammalian loci. Here, we applied computational analysis to identify regions of homology in the 5' upstream sequences of the human tyrosinase gene, similar to the locus control region (LCR) of the mouse tyrosinase gene, located at -15 kb. We detected several stretches of homology within the first 30 kb 5' tyrosinase gene upstream sequences of both species that include the proximal promoter sequences, the genomic region surrounding the mouse LCR, and further upstream segments. We cloned and sequenced a 5' upstream regulatory sequence found between -8 and -10 kb of the human tyrosinase locus (termed h5'URS) homologous to the mouse LCR sequences, and confirmed the presence of putative binding sites at -9 kb, homologous to those described in the mouse tyrosinase LCR core. Finally, we functionally validated the presence of a tissue-specific enhancer in the h5'URS by transient transfection analysis in human and mouse cells, as compared with homologous DNA sequences from the mouse tyrosinase locus. Future experiments in cells and transgenic animals will help us to understand the in vivo relevance of this newly described h5'URS sequence as a potentially important regulatory element for the correct expression of the human tyrosinase gene.
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Affiliation(s)
- Lucía Regales
- Department of Molecular and Cellular Biology, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, Madrid, Spain
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16
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Tepper AWJW, Bubacco L, Canters GW. Stopped-flow Fluorescence Studies of Inhibitor Binding to Tyrosinase from Streptomyces antibioticus. J Biol Chem 2004; 279:13425-34. [PMID: 14699163 DOI: 10.1074/jbc.m309367200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosinase (Ty) is a type 3 copper protein involved in the rate-limiting step of melanin synthesis. It is shown that the endogenous Trp fluorescence of tyrosinase from Streptomyces antibioticus is remarkably sensitive to the redox state. The fluorescence emission intensity of the [(Cu(I) Cu(I)] reduced species is more than twice that of the oxygen-bound [Cu(II)-O(2)(2-)-Cu(II)] form. The emission intensity of the oxidized [Cu(II)-OH(-)-Cu(II)] protein (Ty(met)) appears to be dependent on an acid-base equilibrium with a pK(a) value of 4.5 +/- 0.1. The binding of fluoride was studied under pseudo first-order conditions using stopped-flow fluorescence spectroscopy. The kinetic parameters k(on), K(d), and the fraction of fluorescence emission quenched upon fluoride binding show a similar pH dependence as above with an average pK(a) value of 4.62 +/- 0.05. Both observations are related to the dissociation of Cu(2)-bridging hydroxide at low pH. It is further shown that Ty is rapidly inactivated at low pH and that halide protects the enzyme from this inactivation. All results support the hypothesis that halide displaces hydroxide as the Cu(2)-bridging ligand in Ty(met). The relevance of the experimental findings for the catalytic cycle is discussed. The data are consistent with the data obtained from other techniques, validating the use of fluorescence quenching as a sensitive and effective tool in studying ligand binding and substrate conversion.
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Affiliation(s)
- Armand W J W Tepper
- Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, Einsteinweg 55, 2333 CC, Leiden, The Netherlands
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17
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Abstract
Oculocutaneous albinism represents a group of inherited skin disorders characterized by a generalized reduction of cutaneous, ocular and pilar pigmentation from the time of birth. Oculocutaneous albinism types 1 and 2 are the most common, but several other types have been described. A defect in the melanin synthesis pathway, resulting in reduced formation of melanin, is responsible for oculocutaneous albinism. Aetiology, clinical manifestations, diagnosis and management are discussed.
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Affiliation(s)
- J F Okulicz
- Department of Dermatology and Paediatrics, New Jersey Medical School, Newark, New Jersey 07103-2714, USA
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18
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Alhaidari, Olivry, Ortonne. Melanocytogenesis and melanogenesis: genetic regulation and comparative clinical diseases. Vet Dermatol 2002; 10:3-16. [DOI: 10.1046/j.1365-3164.1999.00132.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Alhaidari
- Clinique Vétérinaire, Cidex 248, R. N. 85, 06330‐Roquefort les Pins, France,
| | - Olivry
- College of Veterinary Medicine, North Carolina State University, 4700 Hillsborough street, Raleigh, NC 27606, USA,
| | - Ortonne
- Hopital de l’Archet II‐Service de Dermatologie, 151, route Saint Antoine de Ginestière‐BP 79, 06202 Nice Cedex 3, France
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19
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Sato S, Tanaka M, Miura H, Ikeo K, Gojobori T, Takeuchi T, Yamamoto H. Functional conservation of the promoter regions of vertebrate tyrosinase genes. J Investig Dermatol Symp Proc 2001; 6:10-8. [PMID: 11764277 DOI: 10.1046/j.0022-202x.2001.00008.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Tyrosinase is the key enzyme for synthesizing melanin pigments, which primarily determine mammalian skin coloration. Considering the important roles of pigments in the evolution and the adaptation of vertebrates, phylogenetic changes in the coding and flanking regulatory sequences of the tyrosinase gene are particularly intriguing. We have now cloned cDNA encoding tyrosinase from Japanese quail and snapping turtle. These nonmammalian cDNA are highly homologous to those of the mouse and human tyrosinases, whereas the 5' flanking sequences are far less conserved except for a few short sequence motifs. Nevertheless, we demonstrate that the 5' flanking sequences from the quail or turtle tyrosinase genes are capable of directing the expression of a fused mouse tyrosinase cDNA when introduced into cultured mouse albino melanocytes. This experimental method, which reveals the functional conservation of regulatory sequences in one cell type (the melanocyte), may be utilized to evaluate phylogenetic differences in mechanisms controlling specific gene expression in many other types of cells. We also provide evidence that the 5' flanking sequences from these nonmammalian genes are functional in vivo by producing transgenic mice. Phylogenetic changes of vertebrate tyrosinase promoters and the possible involvement of conserved sequence motifs in melanocyte-specific expression of tyrosinase are discussed.
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Affiliation(s)
- S Sato
- Biological Institute, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
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20
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Toyofuku K, Wada I, Valencia JC, Kushimoto T, Ferrans VJ, Hearing VJ. Oculocutaneous albinism types 1 and 3 are ER retention diseases: mutation of tyrosinase or Tyrp1 can affect the processing of both mutant and wild-type proteins. FASEB J 2001; 15:2149-61. [PMID: 11641241 DOI: 10.1096/fj.01-0216com] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Various types of oculocutaneous albinism (OCA) are associated with reduced pigmentation in the skin, hair, and eyes that results from mutations in genes involved in melanin synthesis. Immortal mouse melanocyte lines (melan-a, melan-b, and melan-c) provide opportune models with which to investigate the etiology of two different types of OCA (types I and III), which arise from mutations in Tyr and Tyrp1, respectively. We compared intracellular processing, sorting, and degradation of tyrosinase and Tyrp1, and the effects on their catalytic function and melanin synthesis, in these wild-type and mutant melanocytes. A mutation in either Tyr or Tyrp1 increased the time of association of tyrosinase and Tyrp1 with calnexin and Bip, which in turn resulted in the retention of these mutant products in the ER. A mutation in either gene selectively enhanced the duration and efficiency of chaperone interactions (even with the wild-type protein in the mutant melanocytes) and markedly slowed their transport to melanosomes. These results show that OCA1 and OCA3 are (in some cases, at least) ER retention diseases wherein a mutation in one melanogenic protein affects the maturation and stability of the other in the melanogenic pathway.
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Affiliation(s)
- K Toyofuku
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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21
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Samaraweera P, Shen B, Newton JM, Barsh GS, Orlow SJ. The mouse ocular albinism 1 gene product is an endolysosomal protein. Exp Eye Res 2001; 72:319-29. [PMID: 11180981 DOI: 10.1006/exer.2000.0962] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To gain insight into the role of Oa1, the mouse homolog of the human X-linked ocular albinism 1 protein, its properties and subcellular localization were investigated. Antiserum raised against an expressed segment of the Oa1 protein recognized a band of approximately 48 kDa in immunoblots of extracts of cultured mouse melan-a melanocytes, but not of cells of non-melanocyte origin. When melanocyte extracts were treated with glycopeptidase F, a approximately 44 kDa band appeared. Like the melanogenic enzyme tyrosinase, expression of Oa1 was stimulated by alpha-melanocyte stimulating hormone and inhibited by agouti signal protein. Upon density gradient centrifugation of organelles of melan-a cells, Oa1 protein colocalized with the late endosomal/lysosomal marker Lamp1, but only partial overlap was observed with melanosomal proteins in the high density region of the gradient. Immunofluorescence staining revealed that neither endogenous Oa1 nor an Oa1-green fluorescent protein fusion product colocalized with the melanosomal protein tyrosinase related protein-1 in the cell periphery. In contrast, colocalization of Oa1 and Oa1-green fluorescent protein fusion product with Lamp1 was extensive throughout the cell. These results indicate that Oa1 is a melanocyte-specific integral membrane glycoprotein localized to late endosomes/lysosomes but not mature melanosomes. Considering the microscopic findings in patients with X-linked ocular albinism 1, we speculate that Oa1 may play a role in the trafficking of vesicles to developing melanosomes.
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Affiliation(s)
- P Samaraweera
- The Ronald O. Perelman Department of Dermatology, NYU School of Medicine, New York, NY 10016, USA
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22
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Abstract
Neonatologists do not require a detailed knowledge of all genetic skin disorders but need to recognize one if they see it. The unique accessibility of the skin makes it possible to observe the physical signs and deduce the child's immediate needs from first principles. The morphological classification given here will help the nondermatologist establish a clinical diagnosis. Tremendous advances over the last 10 years in understanding the molecular basis of skin disease make it possible, in many cases, to confirm the diagnosis and to counsel the family accurately.
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Affiliation(s)
- C Moss
- Birmingham Children's Hospital, Steelhouse Lane, Birmingham, UK.
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23
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Abstract
This article summarizes several malignant childhood neoplasms and benign tumors that can mimic malignancies. Because malignant skin tumors are rare in children, parents and physicians often are not sufficiently suspicious to ensure that an early diagnosis can be made. Many malignant skin tumors have features that suggest a vascular or hemangioma-like lesion. Because hemangiomas occur in 10% of infants, it is often considered prudent to adopt a wait-and-see attitude; however, if the lesion is too firm to be a hemangioma or its growth pattern does not follow that of a typical hemangioma, additional options should be considered. To manage childhood skin malignancies, one needs expert consultation, early biopsy, and correct histopathologic interpretation.
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Affiliation(s)
- A J Wyatt
- Department of Medicine (Dermatology), University of Arizona College of Medicine, Tucson, USA
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24
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Yang F, Sarangarajan R, Le Poole IC, Medrano EE, Boissy RE. The cytotoxicity and apoptosis induced by 4-tertiary butylphenol in human melanocytes are independent of tyrosinase activity. J Invest Dermatol 2000; 114:157-64. [PMID: 10620132 DOI: 10.1046/j.1523-1747.2000.00836.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has been known for several decades that cutaneous depigmentation, i.e., contact/occupational vitiligo, can be caused by some phenolic derivatives that have a similar structure to tyrosine. Among these phenolic depigmenting agents, 4-tertiary butylphenol is the most potent. The cutaneous depigmentation induced by phenolic derivatives results from the loss of functional melanocytes. Tyrosinase is a melanocyte specific copper-containing enzyme that catalyzes the conversion of the amino acid tyrosine, through a complex series of intermediates, to melanin. In this study we tested the hypothesis that the cytotoxicity induced by 4-tertiary butylphenol is mediated by tyrosinase and occurs via an apoptotic process. Melanocyte cultures derived from African-American and Caucasian donors exhibiting a 3-fold difference in tyrosinase activity and 14-fold difference in melanin content demonstrate comparable concentration-dependent sensitivity to 4-tertiary butylphenol. In addition, cultures of dermal fibroblasts and epidermal keratinocytes exhibited similar and reduced sensitivity, respectively, to 4-tertiary butylphenol compared with autologous melanocytes. Two melanoma cell lines, one melanotic and one amelanotic lacking the expression of both tyrosinase protein and activity, when transfected with the tyrosinase cDNA, exhibited no alteration in its sensitivity to 4-tertiary butylphenol. These data suggest that 4-tertiary butylphenol cytotoxicity is not mediated via tyrosinase. Melanocytes treated with 4-tertiary butylphenol, however, did exhibit plasma membrane blebbing, DNA fragmentation, and phosphatidylserine relocalization indicating that 4-tertiary butylphenol induced melanocyte destruction occurs by an apoptotic process.
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Affiliation(s)
- F Yang
- Department of Dermatology, University of Cincinnati, OH 45267-0592, USA
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25
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Rosenmann E, Rosenmann A, Ne'eman Z, Lewin A, Bejarano-Achache I, Blumenfeld A. Prenatal diagnosis of oculocutaneous albinism type I: review and personal experience. Pediatr Dev Pathol 1999; 2:404-14. [PMID: 10441617 DOI: 10.1007/s100249900143] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Oculocutaneous albinism type I (OCA I) comprises autosomal recessive syndromes of hypopigmentation and low vision, caused by the lack of tyrosinase activity. Affected families seek genetic counseling and prenatal diagnosis as preventive measures. Until recently, prenatal diagnosis of OCA I was achieved by histologic and electron microscopic examination of fetal skin biopsies. Lately, a molecular genetic approach has become possible by the identification of the two mutated copies of the TYR gene, coding the tyrosinase, in which over 60 mutations have been identified. We report here our experience in prenatal diagnosis of OCA I using the two strategies. Thirty-four prenatal tests were performed in fetuses at risk for OCA I. In 31 cases the diagnosis was made in fetal scalp biopsies using the histological approach. The microscopic observations revealed normal melanogenesis in 26 biopsies. Five albino fetuses were diagnosed by the demonstration of arrest of melanogenesis in early stages I and II. In three pregnancies, molecular genetic tests were performed on DNA extracted from amniocytes, using direct mutation analysis (in one), and complemented by linkage analysis (in two). One albino and two normally pigmented fetuses were diagnosed. The prenatal molecular genetic test can be applied to families when at least one mutation is diagnosed in the albino patient. The histological approach is applicable in all families at risk for OCA I.
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Affiliation(s)
- E Rosenmann
- Department of Pathology, Hadassah University Hospital, Kyriat Hadassah, PO Box 12000, Jerusalem 91120, Israel
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26
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Boissy RE, Sakai C, Zhao H, Kobayashi T, Hearing VJ. Human tyrosinase related protein-1 (TRP-1) does not function as a DHICA oxidase activity in contrast to murine TRP-1. Exp Dermatol 1998; 7:198-204. [PMID: 9758418 DOI: 10.1111/j.1600-0625.1998.tb00324.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tyrosinase related protein-1 is a melanocyte specific protein and a member of the tyrosinase gene family which also includes tyrosinase and TRP 2 (DOPAchrome tautomerase). In murine melanocytes, TRP-1 functions as a 5,6-dihydroxyindole-2-carboxylic acid [DHICA] oxidase during the biosynthetic conversion of tyrosine to eumelanin and mutations affecting TRP-1 result in the synthesis of brown rather than black pelage coloration. In this study, we examined the putative DHICA oxidase activity of TRP-1 in human melanocytes using several approaches. We first utilized a line of cultured melanocytes established from a patient with a form of oculocutaneous albinism completely lacking expression of TRP-1 (OCA3). This line of melanocytes endogenously exhibited the same amount of DHICA oxidase activity as control melanocytes expressing TRP-1. In other experiments, cultured human fibroblasts were transfected with a cDNA for TRP-1, in either the sense or antisense direction, or with the retroviral vector alone. TRP-1 expression was induced in fibroblasts transfected with the TRP-1 cDNA in the sense direction only. Although TRP-1 was expressed by sense-transfected cells, there was no significant DHICA oxidase activity above controls. These results demonstrate that human TRP-1 does not use DHICA as a substrate for oxidation.
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Affiliation(s)
- R E Boissy
- Department of Dermatology, University of Cincinnati College of Medicine, OH, USA.
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Le Fur N, Kelsall SR, Silvers WK, Mintz B. Selective increase in specific alternative splice variants of tyrosinase in murine melanomas: a projected basis for immunotherapy. Proc Natl Acad Sci U S A 1997; 94:5332-7. [PMID: 9144237 PMCID: PMC24678 DOI: 10.1073/pnas.94.10.5332] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Melanomas tend to become less pigmented in the course of malignant progression. Thus, as proliferation increases, the tumors are decreasingly characterized by the tissue-specific phenotype of normally differentiated melanocytes. To learn whether the decline in melanization is associated with a shift from constitutive to alternative splicing of some pigment gene pre-mRNAs, melanomas were collected from Tyr-SV40E transgenic mice of the standard C57BL/6 strain. The mRNAs of the tyrosinase gene, which has a key role in melanogenesis, were analyzed by quantitative reverse transcriptase-PCR in 34 samples from 16 cutaneous tumors and 9 metastases. The cutaneous tumors included some cases with distinct melanotic and amelanotic zones, which were separately analyzed. All tyrosinase transcripts found in the melanomas were also found in normal skin melanocytes. However, the Delta1b and Delta1d alternatively spliced transcripts, due to deletions within the first exon, were specifically augmented in most of the tumors over their very low levels in skin; the exceptions were some all-amelanotic tumors in which no tyrosinase transcripts were detected. The level of Delta1b rose as high as 11.3% of total tyrosinase mRNAs as compared with 0.6% in skin; Delta1d reached 4.0% as compared with 0. 8% in skin. Expression of these splice variants was highest in the melanotic components of zonal primary tumors, relatively lower in their amelanotic components, and still lower in all-amelanotic primary tumors and amelanotic metastases. The increase in Delta1b and Delta1d transcripts may be predicted to increase the levels of unusual peptides, which could have antigenic potential in the tumors, especially in the relatively early phases of malignancy. Analyses of the alternative transcripts of other pigment genes may identify additional candidate antigens, ultimately enabling melanoma cells in all phases of the disease to be represented as a basis for immune intervention.
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Affiliation(s)
- N Le Fur
- Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111, USA
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28
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Abstract
Albinism connotes a large group of genetic disorders that are characterized by diminished ocular and oftentimes cutaneous pigmentation. These disorders are generally subclassified as oculocutaneous albinism (OCA) or ocular albinism (OA) based on the extent of their effects on the pigmentation of the skin and hair. Sometimes, different mutations in the same gene can cause OCA or OA.
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Affiliation(s)
- S J Orlow
- New York University Medical Center, New York 10016, USA
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29
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Boissy RE, Nordlund JJ. Molecular basis of congenital hypopigmentary disorders in humans: a review. PIGMENT CELL RESEARCH 1997; 10:12-24. [PMID: 9170158 DOI: 10.1111/j.1600-0749.1997.tb00461.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Many specific gene products are sequentially made and utilized by the melanocyte as it emigrates from its embryonic origin, migrates into specific target sites, synthesizes melanin(s) within a specialized organelle, transfers pigment granules to neighboring cells, and responds to various exogenous cues. A mutation in many of the respective encoding genes can disrupt this process of melanogenesis and can result in hypopigmentary disorders. Following are examples highlighting this scenario. A subset of neural crest derived cells emigrate from the dorsal surface of the neural tube, become committed to the melanoblast lineage, and are targeted along the dorsal lateral pathway. The specific transcription factors PAX3 and MITF (microphthalmia transcription factor) appear to play a regulatory role in early embryonic development of the pigment system and in associated diseases (the Waardenburg syndromes). During the subsequent development and commitment of the melanoblast, concomitant expression of the receptors for fibroblasts growth factor (FGFR2), endothelin-B (EDNRB), and steel factor (cKIT) also appears essential for the continued survival of migrating melanoblasts. Lack or dysfunction of these receptors result in Apert syndrome, Hirschsprung syndrome and piebaldism, respectively. Once the melanocyte resides in its target tissue, a plethora of melanocyte specific enzymes and structural proteins are coordinately expressed to form the melanosome and to convert tyrosine to melanin within it. Mutations in the genes encoding these proteins results in a family of congenital hypopigmentary diseases called oculocutaneous albinism (OCA). The tyrosinase gene family of proteins (tyrosinase, TRP1, and TRP2) regulate the type of eumelanin synthesized and mutations affecting them result in OCA1, OCA3, and slaty (in the murine system), respectively. The P protein, with 12 transmembrane domains localized to the melanosome, has no assigned function as of yet but is responsible for OCA2 when dysfunctional. There are other genetically based syndromes, phenotypically resembling albinism, in which the synthesis of pigmented melanosomes, as well as specialized organelles of other cell types, is compromised. The Hermansky-Pudlak syndrome (HPS) and the Chediak-Higashi syndrome (CHS) are two such disorders. Eventually, the functional melanocyte must be maintained in the tissue throughout life. In some cases it is lost either normally or prematurely. White hair results in the absence of melanocytes repopulating the germinative hair follicle during subsequent anagen stages. Vitiligo, in contrast, results from the destruction and removal of the melanocyte in the epidermis and mucous membranes.
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Affiliation(s)
- R E Boissy
- Department of Dermatology, University of Cincinnati College of Medicine, Ohio 45267-0592, USA
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30
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Affiliation(s)
- Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305
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31
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Matsunaga J, Dakeishi M, Shimizu H, Tomita Y. R278TER and P431L mutations of the tyrosinase gene exist in Japanese patients with tyrosinase-negative oculocutaneous albinism. J Dermatol Sci 1996; 13:134-9. [PMID: 8953413 DOI: 10.1016/s0923-1811(96)00519-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We examined the tyrosinase gene of two Japanese patients with tyrosinase-negative oculocutaneous albinism by allele-specific amplification analysis on two known point mutations in Japanese, and the results indicated that they were compound heterozygouts, namely, one allele of the tyrosinase gene harbored one of two known mutations and another allele probably had a mutation unknown in Japanese patients. Therefore, we have cloned and sequenced the tyrosinase gene of the two patients and identified two different point mutations. One is a nonsense mutation, codon 278CGA (Arg) to TGA (TER), and the other is a substitution mutation, codon 431CCA (Pro) to CTA (Leu). However, these same mutations have already been observed in a Guyanan and a Moroccan Jewish patient, and in an Indo-Pakistani patient, respectively.
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Affiliation(s)
- J Matsunaga
- Department of Dermatology, Akita University School of Medicine, Japan
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32
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Tief K, Hahne M, Schmidt A, Beermann F. Tyrosinase, the key enzyme in melanin synthesis, is expressed in murine brain. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 241:12-6. [PMID: 8898882 DOI: 10.1111/j.1432-1033.1996.0012t.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Tyrosinase is one of the key enzymes in mammalian melanin synthesis. The pigment is produced in two different cell types: the pigmented epithelial cell of the retina, and the melanocyte, a cell of neural-crest origin. We recently showed that a fusion gene between regulatory sequences of tyrosinase gene (tyr) and the beta-galactosidase gene (lacZ), when introduced into transgenic mice, resulted in embryonic expression in presumptive pigment cells but also in cells populations along the entire neural tube. This expression in the developing brain was striking, and we therefore asked whether this would still be detectable after birth. Transgenic mice carrying the tyr-lacZ fusion gene showed beta-galactosidase expression in adult brain. On Western blots, we detected tyrosinase-specific bands of 65-68 kDa in brain and eye. Using an affinity-purified antibody, we showed that detection of tyrosinase is specific and competed off by the presence of the cognate tyrosinase-derived peptide. However, neither tyrosine hydroxylase nor Dopa oxidase activity were detected in protein extracts of brain. We therefore suggest that tyrosinase is present in brain but either not functional or catalyzing different reactions compared to pigment cells.
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Affiliation(s)
- K Tief
- Swiss Institute for Experimental Cancer Research, Epalinges, Switzerland
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33
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Oetting WS, Brilliant MH, King RA. The clinical spectrum of albinism in humans. MOLECULAR MEDICINE TODAY 1996; 2:330-5. [PMID: 8796918 DOI: 10.1016/1357-4310(96)81798-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Oculocutaneous albinism is characterized by a congenital reduction or absence of melanin pigment in the skin, hair and eyes. The reduction in the hair and skin results in a change in color but no change in the development or function of these tissues, while the absence of melanin pigment in the eye leads to abnormal development and function. Of particular interest are mutations that are associated with a slow accumulation of pigment in the hair and eyes over time, while retaining the ocular defects of albinism. Analysis of these mutations might provide the insight that we need to understand the interaction between the pigment system and the development of the optic system.
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Affiliation(s)
- W S Oetting
- Department of Medicine, University of Minnesota, Minneapolis 55455, USA.
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34
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Abstract
Tyrosinase is the key enzyme in pigment synthesis, initiating a cascade of reactions which convert the amino acid tyrosine to the melanin biopolymer. Two other tyrosinase-related proteins (TRP) are known, TRP-1 (probably DHICAoxidase) and TRP-2 (DOPAchrome tautomerase). These proteins show about 40% homology, and recent results have indicated that the genes might be derived from a common ancestor. We will discuss recent findings on genomic organization, and on the proteins and their presumed function, which is important for eumelanin synthesis in mouse and man.
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Affiliation(s)
- V del Marmol
- LOCE, Institut J. Bordet, Université Libre de Bruxelles, Belgium
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35
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Potterf SB, Muller J, Bernardini I, Tietze F, Kobayashi T, Hearing VJ, Gahl WA. Characterization of a melanosomal transport system in murine melanocytes mediating entry of the melanogenic substrate tyrosine. J Biol Chem 1996; 271:4002-8. [PMID: 8626732 DOI: 10.1074/jbc.271.8.4002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In this study, we identify a transport system for tyrosine, the initial precursor of melanin synthesis, in the melanosomes of murine melanocytes. Melanosomes preloaded with tyrosine demonstrated countertransport of 10 microM [3H]tyrosine, indicating carrier-mediated transport. Melanosomal tyrosine transport was saturable, with an apparent Km for tyrosine transport of 54 microM and a maximal velocity of 15 pmol of tyrosine/unit of hexosaminidase/min. Transport was temperature-dependent (Ea = 7.5 kcal/mol) and showed stereospecificity for the l-isomer of tyrosine. Aromatic, neutral hydrophobic compounds (such as tryptophan and phenylalanine), as well as the small, bulky neutral amino acids (such as leucine, isoleucine, and methionine) competed for tyrosine transport. Tyrosine transport was inhibited by the classical system L analogue, 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid and by monoiodotyrosine, but not by cystine, lysine, glutamic acid, or 2-(methylamino)-isobutyric acid. Tyrosine transport showed no dependence on Na+ or K+, and did not require an acidic environment or the availability of free thiols. These results demonstrate the existence of a neutral amino acid carrier in murine melanocyte melanosomes which resembles the rat thyroid FRTL-5 lysosomal system h. This transport system is critical to the function of the melanosome since tyrosine is the essential substrate required for the synthesis of the pigment melanin.
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Affiliation(s)
- S B Potterf
- Laboratory of Cell Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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36
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Matsunaga J, Tomita Y, Tagami H. Detection of point mutations in human tyrosinase gene by improved allele-specific amplification. Exp Dermatol 1995; 4:377-81. [PMID: 8608346 DOI: 10.1111/j.1600-0625.1995.tb00063.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Allele-specific amplification (ASA) is a simple and non-radioactive technique for detecting known point mutations that produce genetic diseases. Although this technique is based on the specific amplification of the target allele by a polymerase chain reaction (PCR) with allele-specific primers, the specificity of the amplification may depend on various PCR conditions. To avoid non-specific amplification which leads to false-positive results in ASA, we modified both the normal and mutant allele-specific primers so that they would have one constant base mismatch, located at the penultimate 3' position. We confirmed that our modification could inhibit such unfavorable amplification by using as templates genomic DNAs of patients affected with tyrosinase-negative oculocutaneous albinism (OCA). We then analyzed new patients affected with tyrosinase-negative OCA, and based the diagnosis on both the results of a clinical examination and those of a hair bulb test using ASA with the modified allele-specific primers. The results indicated that more than 3 alleles of the tyrosinase gene with a pathological mutation existed in Japanese patients.
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Affiliation(s)
- J Matsunaga
- Department of Dermatology, Tohoku University School of Medicine, Sendai, Japan
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37
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Abstract
The term oculocutaneous albinism (OCA) covers a range of autosomal recessive genetic conditions involving hypopigmentation of the skin, hair, and eyes. In southern African black ethnic groups the tyrosinase positive form, OCA2, is predominant, with few cases of tyrosinase negative OCA1. The prevalence of OCA2 in schoolchildren in Harare, the capital city of Zimbabwe, was found to be 1 in 2833. The gene frequency for OCA2 was 0.0188, with a carrier frequency of 1 in 27. Most of the pupils with albinism belong to the majority Shona ethnic group. As consanguineous marriages are discouraged in the Shona culture this high rate is likely to be a result of genetic drift in a relatively small population showing limited mobility. OCA pupils were found in more than a third of the secondary schools in Harare, emphasising the importance of distributing information on albinism and its management widely throughout the school system.
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Affiliation(s)
- F Kagore
- Department of Biological Sciences, University of Zimbabwe, Harare, Zimbabwe
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