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Sergouniotis PI, Michaud V, Lasseaux E, Campbell C, Plaisant C, Javerzat S, Birney E, Ramsden SC, Black GC, Arveiler B. A multilayered approach to the analysis of genetic data from individuals with suspected albinism. J Med Genet 2023; 60:1245-1249. [PMID: 37460203 DOI: 10.1136/jmg-2022-109088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Accepted: 05/12/2023] [Indexed: 11/29/2023]
Abstract
Albinism is a clinically and genetically heterogeneous group of conditions characterised by visual abnormalities and variable degrees of hypopigmentation. Multiple studies have demonstrated the clinical utility of genetic investigations in individuals with suspected albinism. Despite this, the variation in the provision of genetic testing for albinism remains significant. One key issue is the lack of a standardised approach to the analysis of genomic data from affected individuals. For example, there is variation in how different clinical genetic laboratories approach genotypes that involve incompletely penetrant alleles, including the common, 'hypomorphic' TYR c.1205G>A (p.Arg402Gln) [rs1126809] variant. Here, we discuss the value of genetic testing as a frontline diagnostic tool in individuals with features of albinism and propose a practice pattern for the analysis of genomic data from affected families.
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Affiliation(s)
- Panagiotis I Sergouniotis
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL- EBI), Wellcome Genome Campus, Cambridge, UK
- Manchester Centre for Genomic Medicine, Saint Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
- Manchester Royal Eye Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Vincent Michaud
- Department of Medical Genetics, University Hospital of Bordeaux, Bordeaux, France
- INSERM U1211, Rare Diseases, Genetics and Metabolism, University of Bordeaux, Bordeaux, France
| | - Eulalie Lasseaux
- Department of Medical Genetics, University Hospital of Bordeaux, Bordeaux, France
| | - Christopher Campbell
- Manchester Centre for Genomic Medicine, Saint Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Claudio Plaisant
- Department of Medical Genetics, University Hospital of Bordeaux, Bordeaux, France
| | - Sophie Javerzat
- INSERM U1211, Rare Diseases, Genetics and Metabolism, University of Bordeaux, Bordeaux, France
| | - Ewan Birney
- European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL- EBI), Wellcome Genome Campus, Cambridge, UK
| | - Simon C Ramsden
- Manchester Centre for Genomic Medicine, Saint Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Graeme C Black
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
- Manchester Centre for Genomic Medicine, Saint Mary's Hospital, Manchester University NHS Foundation Trust, Manchester, UK
| | - Benoit Arveiler
- Department of Medical Genetics, University Hospital of Bordeaux, Bordeaux, France
- INSERM U1211, Rare Diseases, Genetics and Metabolism, University of Bordeaux, Bordeaux, France
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Zhu YM, Li Q, Gao X, Li YF, Liu YL, Dai P, Li XP. Familial Temperature-Sensitive Auditory Neuropathy: Distinctive Clinical Courses Caused by Variants of the OTOF Gene. Front Cell Dev Biol 2021; 9:732930. [PMID: 34692690 PMCID: PMC8529165 DOI: 10.3389/fcell.2021.732930] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 08/31/2021] [Indexed: 11/13/2022] Open
Abstract
Objective: To investigate the clinical course and genetic etiology of familial temperature-sensitive auditory neuropathy (TSAN), which is a very rare subtype of auditory neuropathy (AN) that involves an elevation of hearing thresholds due to an increase in the core body temperature, and to evaluate the genotype-phenotype correlations in a family with TSAN. Methods: Six members of a non-consanguineous Chinese family, including four siblings complaining of communication difficulties when febrile, were enrolled in this study. The clinical and audiological profiles of the four siblings were fully evaluated during both febrile and afebrile episodes, and the genetic etiology of hearing loss (HL) was explored using next-generation sequencing (NGS) technology. Their parents, who had no complaints of fluctuating HL due to body temperature variation, were enrolled for the genetics portion only. Results: Audiological tests during the patients' febrile episodes met the classical diagnostic criteria for AN, including mild HL, poor speech discrimination, preserved cochlear microphonics (CMs), and absent auditory brainstem responses (ABRs). Importantly, unlike the pattern observed in previously reported cases of TSAN, the ABRs and electrocochleography (ECochG) signals of our patients improved to normal during afebrile periods. Genetic analysis identified a compound heterozygous variant of the OTOF gene (which encodes the otoferlin protein), including one previously reported pathogenic variant, c.5098G > C (p.Glu1700Gln), and one novel variant, c.4882C > A (p.Pro1628Thr). Neither of the identified variants affected the C2 domains related to the main function of otoferlin. Both variants faithfully cosegregated with TSAN within the pedigree, suggesting that OTOF is the causative gene of the autosomal recessive trait segregation in this family. Conclusion: The presence of CMs with absent (or markedly abnormal) ABRs is a reliable criterion for diagnosing AN. The severity of the phenotype caused by dysfunctional neurotransmitter release in TSAN may reflect variants that alter the C2 domains of otoferlin. The observations from this study enrich the current understanding of the phenotype and genotype of TSAN and may lay a foundation for further research on its pathogenesis.
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Affiliation(s)
- Yi-Ming Zhu
- Department of Otolaryngology-Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Otolaryngology-Head and Neck Surgery, Lanzhou University Second Hospital, Lanzhou, China
| | - Qi Li
- Department of Otolaryngology-Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Xue Gao
- Department of Otolaryngology, PLA Rocket Force Characteristic Medical Center, Beijing, China
| | - Yan-Fei Li
- Department of Otolaryngology-Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - You-Li Liu
- Department of Otolaryngology-Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Pu Dai
- Department of Otolaryngology-Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
- Department of Otolaryngology-Head and Neck Surgery, Chinese PLA General Hospital, Beijing, China
| | - Xiang-Ping Li
- Department of Otolaryngology-Head and Neck Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
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Characterization of Temperature-Dependent Kinetics of Oculocutaneous Albinism-Causing Mutants of Tyrosinase. Int J Mol Sci 2021; 22:ijms22157771. [PMID: 34360537 PMCID: PMC8346126 DOI: 10.3390/ijms22157771] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/12/2021] [Accepted: 07/16/2021] [Indexed: 01/06/2023] Open
Abstract
Human tyrosinase (Tyr) is a glycoenzyme that catalyzes the first and rate-limiting step in melanin production, and its gene (TYR) is mutated in many cases of oculocutaneous albinism type 1 (OCA1). The mechanisms by which individual mutations contribute to the diverse pigmentation phenotype in patients with OCA1 have only began to be examined and remain to be delineated. Here, we analyze the temperature-dependent kinetics of wild-type Tyr (WT) and two OCA1B mutant variants (R422Q and P406L) using Michaelis–Menten and Van’t Hoff analyses. Recombinant truncated human Tyr proteins (residues 19–469) were produced in the whole insect Trichoplusia Ni larvae. Proteins were purified by a combination of affinity and size-exclusion chromatography. The temperature dependence of diphenol oxidase protein activities and kinetic parameters were measured by dopachrome absorption. Using the same experimental conditions, computational simulations were performed to assess the temperature-dependent association of L-DOPA and Tyr. Our results revealed, for the first time, that the association of L-DOPA with R422Q and P406L followed by dopachrome formation is a complex reaction supported by enthalpy and entropy forces. We show that the WT has a higher turnover number as compared with both R422Q and P406L. Elucidating the kinetics and thermodynamics of mutant variants of Tyr in OCA1B helps to understand the mechanisms by which they lower Tyr catalytic activity and to discover novel therapies for patients.
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Bredrup C, Cristea I, Safieh LA, Di Maria E, Gjertsen BT, Tveit KS, Thu F, Bull N, Edward DP, Hennekam RCM, Høvding G, Haugen OH, Houge G, Rødahl E, Bruland O. Temperature-dependent autoactivation associated with clinical variability of PDGFRB Asn666 substitutions. Hum Mol Genet 2021; 30:72-77. [PMID: 33450762 PMCID: PMC8033145 DOI: 10.1093/hmg/ddab014] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 11/14/2022] Open
Abstract
Ocular pterygium-digital keloid dysplasia (OPDKD) presents in childhood with ingrowth of vascularized connective tissue on the cornea leading to severely reduced vision. Later the patients develop keloids on digits but are otherwise healthy. The overgrowth in OPDKD affects body parts that typically have lower temperature than 37°C. We present evidence that OPDKD is associated with a temperature sensitive, activating substitution, p.(Asn666Tyr), in PDGFRB. Phosphorylation levels of PDGFRB and downstream targets were higher in OPDKD fibroblasts at 37°C but were further greatly increased at the average corneal temperature of 32°C. This suggests that the substitution cause significant constitutive autoactivation mainly at lower temperature. In contrast, a different substitution in the same codon, p.(Asn666Ser), is associated with Penttinen type of premature aging syndrome. This devastating condition is characterized by widespread tissue degeneration, including pronounced chronic ulcers and osteolytic resorption in distal limbs. In Penttinen syndrome fibroblasts, equal and high levels of phosphorylated PDGFRB was present at both 32°C and 37°C. This indicates that this substitution causes severe constitutive autoactivation of PDGFRB regardless of temperature. In line with this, most downstream targets were not affected by lower temperature. However, STAT1, important for tissue wasting, did show further increased phosphorylation at 32°C. Temperature-dependent autoactivation offers an explanation to the strikingly different clinical outcomes of substitutions in the Asn666 codon of PDGFRB.
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Affiliation(s)
- Cecilie Bredrup
- Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway.,Department of Clinical Medicine, University of Bergen, Bergen 5020, Norway.,Department of Medical Genetics, Haukeland University Hospital, Bergen 5021, Norway
| | - Ileana Cristea
- Department of Clinical Medicine, University of Bergen, Bergen 5020, Norway
| | - Leen Abu Safieh
- Research Department, King Khaled Eye Specialist Hospital, Riyadh 11462, Kingdom of Saudi Arabia.,Genomics Research Department, Research Center, King Fahad Medical City, Riyadh 11564, Kingdom of Saudi Arabia
| | - Emilio Di Maria
- Department of Health Sciences, University of Genova, Genova 16132, Italy.,Unit of Medical Genetics, Galliera Hospital, Genova 16128, Italy
| | - Bjørn Tore Gjertsen
- Department of Oncology and Medical Physics, Haukeland University Hospital, Bergen 5021, Norway
| | - Kåre Steinar Tveit
- Department of Dermatology, Haukeland University Hospital, Bergen 5021, Norway
| | - Frode Thu
- Department of Orthopaedic Surgery, Oslo University Hospital, Oslo 4956, Norway
| | - Nils Bull
- Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway
| | - Deepak P Edward
- Research Department, King Khaled Eye Specialist Hospital, Riyadh 11462, Kingdom of Saudi Arabia.,Department of Ophthalmology and Visual Sciences, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Raoul C M Hennekam
- Department of Pediatrics, Amsterdam University Medical Center, University of Amsterdam, Amsterdam 1105AZ, the Netherlands
| | - Gunnar Høvding
- Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway.,Department of Clinical Medicine, University of Bergen, Bergen 5020, Norway
| | - Olav H Haugen
- Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway.,Department of Clinical Medicine, University of Bergen, Bergen 5020, Norway
| | - Gunnar Houge
- Department of Medical Genetics, Haukeland University Hospital, Bergen 5021, Norway
| | - Eyvind Rødahl
- Department of Ophthalmology, Haukeland University Hospital, Bergen 5021, Norway.,Department of Clinical Medicine, University of Bergen, Bergen 5020, Norway
| | - Ove Bruland
- Department of Medical Genetics, Haukeland University Hospital, Bergen 5021, Norway
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Okamura K, Suzuki T. Current landscape of Oculocutaneous Albinism in Japan. Pigment Cell Melanoma Res 2020; 34:190-203. [PMID: 32969595 DOI: 10.1111/pcmr.12927] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/05/2020] [Accepted: 09/10/2020] [Indexed: 12/16/2022]
Abstract
Oculocutaneous albinism (OCA), which is roughly divided into non-syndromic and syndromic OCA, is a group of autosomal recessive disorders caused by mutations in genes associated with pigmentation. Patients with OCA have hypopigmentation and ocular manifestations such as photophobia, amblyopia, and nystagmus. Hermansky-Pudlak syndrome (HPS), the most common syndromic OCA, is characterized by the additional features of a bleeding tendency and other critical systemic comorbidities such as pulmonary fibrosis and immunodeficiency. NGS-based gene analyses have identified several new causative genes for OCA and have detected rare subtypes of OCA with high accuracy including Japanese patients. In our survey of 190 Japanese OCA patients/families, OCA4 is the most common subtype (25.3%) followed by OCA1 (20.0%), HPS1 (14.7%), and OCA2 (8.4%). Similar to the A481T variant in OCA2, which is associated with a mild form of OCA2 and skin color variation, the c.-492_489delAATG variant located in the promoter region of SLC45A2 has been uniquely identified in Japanese patients with a mild form of OCA4. Further, rare OCA subtypes, including OCA3, HPS2, HPS3, HPS4, HPS5, HPS6, and HPS9, have also been identified in Japanese patients. The clinical characteristics and underlying molecular mechanisms of each subtype of OCA are concisely summarized in this review.
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Affiliation(s)
- Ken Okamura
- Department of Dermatology, Faculty of Medicine, Yamagata University, Yamagata, Japan
| | - Tamio Suzuki
- Department of Dermatology, Faculty of Medicine, Yamagata University, Yamagata, Japan
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Giocanti-Aurégan A, Gazeau G, Hrarat L, Lévy V, Amari F, Bodaghi B, Fajnkuchen F. Ethnic differences in normal retinal capillary density and foveal avascular zone measurements. Int Ophthalmol 2020; 40:3043-3048. [PMID: 32601962 DOI: 10.1007/s10792-020-01488-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 06/20/2020] [Indexed: 11/25/2022]
Abstract
BACKGROUND The purpose of this study was to quantify retinal capillary density and foveal avascular zone (FAZ) area in healthy subjects according to their ethnicity, using optical coherence tomography angiography (OCTA). METHODS In this cross-sectional study, all eyes underwent swept-source OCTA (Triton, Topcon, Tokyo, Japan). Macular OCTA scans (3 × 3 mm) were obtained in healthy white Caucasian and black African subjects. The FAZ area and capillary density in both the superficial (SCP) and deep capillary plexuses (DCP) were automatically measured using a custom-made software combining vessel binarization and skeletonization. RESULTS Twelve eyes of 12 healthy Caucasians and 15 eyes of 15 healthy black Africans were included in the analysis. The mean FAZ area was significantly smaller, and the overall vessel density (VD) was higher in the SCP and DCP of Caucasians compared to black Africans. The mean FAZ area was 0.26 ± 0.008 mm2 in the SCP and 0.25 ± 0.05 mm2 in the DCP in Caucasians versus 0.33 ± 0.08 mm2 in the SCP (p = 0.01) and 0.37 ± 0.1 mm2 in the DCP (p = 0.03) in Africans. In the SCP and DCP, the mean VD was, respectively, 40.5 ± 0.8% and 47.1 ± 0.5% in Caucasians versus 34.3 ± 1% (p = 0.008) and 40.6 ± 0.9% in Africans (p < 0.001). DISCUSSION/CONCLUSION In the SCP and DCP, VD is lower in black Africans compared to Caucasians. In OCTA studies on vascular diseases, ethnicity-matched measurements from healthy subjects should be used for comparisons.
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Affiliation(s)
| | - Gaspard Gazeau
- Clinical Research Department, Avicenne Hospital, 125 rue de Stalingrad, Bobigny, France
| | - Linda Hrarat
- Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000, Bobigny, France
| | - Vincent Lévy
- Clinical Research Department, Avicenne Hospital, 125 rue de Stalingrad, Bobigny, France
| | - Fatima Amari
- Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000, Bobigny, France
| | - Bahram Bodaghi
- Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000, Bobigny, France
- Ophthalmology Department, Pitié Salpétrière Hospital, 91 boulevard de l'hôpital, Paris, France
| | - Franck Fajnkuchen
- Ophthalmology Department, Avicenne Hospital, 125 rue de Stalingrad, 93000, Bobigny, France
- Centre d'imagerie et de Laser, 11 rue Antoine Bourdelle, Paris, France
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Mériot M, Hitte C, Rimbault M, Dufaure de Citres C, Gache V, Abitbol M. Donskoy cats as a new model of oculocutaneous albinism with the identification of a splice-site variant in Hermansky-Pudlak Syndrome 5 gene. Pigment Cell Melanoma Res 2020; 33:814-825. [PMID: 32558164 DOI: 10.1111/pcmr.12906] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 06/05/2020] [Accepted: 06/11/2020] [Indexed: 01/15/2023]
Abstract
In the feline Donskoy breed, a phenotype that breeders call "pink-eye," with associated light-brown skin, yellow irises and red-eye effect, has been described. Genealogical data indicated an autosomal recessive inheritance pattern. A single candidate region was identified by genome-wide association study and SNP-based homozygosity mapping. Within that region, we further identified HPS5 (HPS5 Biogenesis Of Lysosomal Organelles Complex 2 Subunit 2) as a strong candidate gene, since HPS5 variants have been identified in humans and animals with Hermansky-Pudlak syndrome 5 or oculocutaneous albinism. A homozygous c.2571-1G>A acceptor splice-site variant located in intron 16 of HPS5 was identified in pink-eye cats. Segregation of the variant was 100% consistent with the inheritance pattern. Genotyping of 170 cats from 19 breeds failed to identify a single carrier in non-Donskoy cats. The c.2571-1G>A variant leads to HPS5 exon-16 splicing that is predicted to produce a 52 amino acids in-frame deletion in the protein. These results support an association of the pink-eye phenotype with the c.2571-1G>A variant. The pink-eye Donskoy cat extends the panel of reported HPS5 variants and offers an opportunity for in-depth exploration of the phenotypic consequences of a new HPS5 variant.
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Affiliation(s)
| | | | | | | | - Vincent Gache
- Univ Lyon, CNRS UMR5310, INSERM U1217, Université Claude Bernard Lyon I, Institut NeuroMyoGène, Lyon, France
| | - Marie Abitbol
- Univ Lyon, VetAgro Sup, Marcy l'Etoile, France.,Univ Lyon, CNRS UMR5310, INSERM U1217, Université Claude Bernard Lyon I, Institut NeuroMyoGène, Lyon, France
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Monfermé S, Lasseaux E, Duncombe-Poulet C, Hamel C, Defoort-Dhellemmes S, Drumare I, Zanlonghi X, Dollfus H, Perdomo Y, Bonneau D, Korobelnik JF, Plaisant C, Michaud V, Pennamen P, Rooryck-Thambo C, Morice-Picard F, Paya C, Arveiler B. Mild form of oculocutaneous albinism type 1: phenotypic analysis of compound heterozygous patients with the R402Q variant of the TYR gene. Br J Ophthalmol 2018; 103:1239-1247. [PMID: 30472657 DOI: 10.1136/bjophthalmol-2018-312729] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 10/23/2018] [Accepted: 11/08/2018] [Indexed: 11/03/2022]
Abstract
AIM Oculocutaneous albinism type 1 (OCA1) is due to TYR mutations. c.1205G>A/p.Arg402Gln (R402Q) is a thermosensitive variant of the TYR gene that has been reported to be responsible for mild forms of OCA1. The aim of our study was to define the phenotype associated with this variant. METHODS In our retrospective series, among 268 patients diagnosed with OCA1, 122 (45.5%) harboured one pathogenic variant of TYR, and the R402Q variant ensured to be in trans by segregation analysis in 69 patients (25.7%), constituting the 'R402Q-OCA1' group. 146 patients harboured two pathogenic variants of the TYR gene other than R402Q. Clinical records were available for 119 of them, constituting the 'Classical-OCA1' group. RESULTS Most R402Q-OCA1 patients presented with white or yellow-white hair at birth (71.43%), blond hair later (46.97%), a light phototype but with residual pigmentation (69.64%), and blue eyes (76.56%). Their pigmentation was significantly higher than in the classical-OCA1 group. All patients from the R402Q-OCA1 group presented with ocular features of albinism. However the prevalence of photophobia (78.13%) and iris transillumination (83.87%) and the severity scores of iris transillumination, retinal hypopigmentation and foveal hypoplasia were lower in the R402Q-OCA1 group. Visual acuity was higher in the R402Q-OCA1 group (0.38±0.21 logarithm of the minimum angle of resolution vs 0.76±0.24). Investigations concerning a possible additive effect of the c.575C>A/p.Ser192 (S192Y) variant of TYR in cis with R402Q, suggested by others, showed no significant impact on the phenotype. CONCLUSION The R402Q variant leads to variable but generally mild forms of albinism whose less typical presentation may lead to underdiagnosis.
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Affiliation(s)
| | - Eulalie Lasseaux
- Service de génétique médicale, CHU de Bordeaux, Bordeaux, France
| | | | - Christian Hamel
- Service d'ophtalmologie, Equipe maladies sensorielles génétiques, CHU de Montpellier, Montpellier, France
| | | | - Isabelle Drumare
- Service d'exploration de la vision et neuro-ophtalmologie, CHRU de Lille, Lille, France
| | | | - Hélène Dollfus
- Centre des affections rares en génétique ophtalmologique, CHU de Strasbourg, Strasbourg, France
| | - Yaurama Perdomo
- Centre des affections rares en génétique ophtalmologique, CHU de Strasbourg, Strasbourg, France
| | | | | | - Claudio Plaisant
- Service de génétique médicale, CHU de Bordeaux, Bordeaux, France
| | - Vincent Michaud
- Service de génétique médicale, CHU de Bordeaux, Bordeaux, France
| | - Perrine Pennamen
- Service de génétique médicale, CHU de Bordeaux, Bordeaux, France.,INSERM U1211, Maladies Rares, Génétique et Métabolisme, Université de Bordeaux, Bordeaux, France
| | - Caroline Rooryck-Thambo
- Service de génétique médicale, CHU de Bordeaux, Bordeaux, France.,INSERM U1211, Maladies Rares, Génétique et Métabolisme, Université de Bordeaux, Bordeaux, France
| | - Fanny Morice-Picard
- Service de dermatologie, Unité de dermato-pédiatrie du CHU de Bordeaux, Bordeaux, France
| | - Clement Paya
- Centre d'ophtalmologie du Palais Gallien, Bordeaux, France
| | - Benoit Arveiler
- Service de génétique médicale, CHU de Bordeaux, Bordeaux, France.,INSERM U1211, Maladies Rares, Génétique et Métabolisme, Université de Bordeaux, Bordeaux, France
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10
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Degradation of Tyrosinase by Melanosomal pH Change and a New Mechanism of Whitening with Propylparaben. COSMETICS 2017. [DOI: 10.3390/cosmetics4040043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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11
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Shahzad M, Yousaf S, Waryah YM, Gul H, Kausar T, Tariq N, Mahmood U, Ali M, Khan MA, Waryah AM, Shaikh RS, Riazuddin S, Ahmed ZM. Molecular outcomes, clinical consequences, and genetic diagnosis of Oculocutaneous Albinism in Pakistani population. Sci Rep 2017; 7:44185. [PMID: 28266639 PMCID: PMC5339803 DOI: 10.1038/srep44185] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/03/2017] [Indexed: 12/31/2022] Open
Abstract
Nonsyndromic oculocutaneous Albinism (nsOCA) is clinically characterized by the loss of pigmentation in the skin, hair, and iris. OCA is amongst the most common causes of vision impairment in children. To date, pathogenic variants in six genes have been identified in individuals with nsOCA. Here, we determined the identities, frequencies, and clinical consequences of OCA alleles in 94 previously unreported Pakistani families. Combination of Sanger and Exome sequencing revealed 38 alleles, including 22 novel variants, segregating with nsOCA phenotype in 80 families. Variants of TYR and OCA2 genes were the most common cause of nsOCA, occurring in 43 and 30 families, respectively. Twenty-two novel variants include nine missense, four splice site, two non-sense, one insertion and six gross deletions. In vitro studies revealed retention of OCA proteins harboring novel missense alleles in the endoplasmic reticulum (ER) of transfected cells. Exon-trapping assays with constructs containing splice site alleles revealed errors in splicing. As eight alleles account for approximately 56% (95% CI: 46.52–65.24%) of nsOCA cases, primarily enrolled from Punjab province of Pakistan, hierarchical strategies for variant detection would be feasible and cost-efficient genetic tests for OCA in families with similar origin. Thus, we developed Tetra-primer ARMS assays for rapid, reliable, reproducible and economical screening of most of these common alleles.
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Affiliation(s)
- Mohsin Shahzad
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Sairah Yousaf
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.,Institute of Molecular Biology &Biotechnology, Bahauddin Zakariya University, Multan, Pakistan
| | - Yar M Waryah
- Molecular Biology &Genetics Department, Medical Research Center, Liaquat University of Medical &Health Sciences, Jamshoro, Pakistan
| | - Hadia Gul
- Gomal Centre of Biochemistry and Biotechnology, Gomal University, D.I. Khan, Pakistan
| | - Tasleem Kausar
- Institute of Molecular Biology &Biotechnology, Bahauddin Zakariya University, Multan, Pakistan
| | - Nabeela Tariq
- Institute of Molecular Biology &Biotechnology, Bahauddin Zakariya University, Multan, Pakistan
| | - Umair Mahmood
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Muhammad Ali
- Government College University, Faisalabad, Pakistan
| | - Muzammil A Khan
- Gomal Centre of Biochemistry and Biotechnology, Gomal University, D.I. Khan, Pakistan
| | - Ali M Waryah
- Molecular Biology &Genetics Department, Medical Research Center, Liaquat University of Medical &Health Sciences, Jamshoro, Pakistan
| | - Rehan S Shaikh
- Institute of Molecular Biology &Biotechnology, Bahauddin Zakariya University, Multan, Pakistan
| | - Saima Riazuddin
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Zubair M Ahmed
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA
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Gradstein L, Hansen RM, Cox GF, Altschwager P, Fulton AB. Progressive retinal degeneration in a girl with Knobloch syndrome who presented with signs of ocular albinism. Doc Ophthalmol 2017; 134:135-140. [DOI: 10.1007/s10633-017-9574-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 01/16/2017] [Indexed: 10/20/2022]
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Lai X, Soler-Lopez M, Wichers HJ, Dijkstra BW. Large-Scale Recombinant Expression and Purification of Human Tyrosinase Suitable for Structural Studies. PLoS One 2016; 11:e0161697. [PMID: 27551823 PMCID: PMC4994950 DOI: 10.1371/journal.pone.0161697] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 08/10/2016] [Indexed: 12/02/2022] Open
Abstract
Human tyrosinase (TYR) is a glycoprotein that initiates the first two reactions in the melanin biosynthesis pathway. Mutations in its encoding gene cause Oculocutaneous Albinism type I (OCA1), the most severe form of albinism, which is a group of autosomal recessive disorders characterized by reduced or absent production of melanin in skin, hair and eyes. Despite extensive structural and characterization studies of its homologues in lower eukaryotic organisms, the catalytic mechanism of human TYR and the molecular basis of OCA1 are largely unknown. In this work, we have carried out a large-scale recombinant expression of TYR that has enabled us to obtain high yields of pure and active protein, required for crystallization trials and screening of skin whitening agents, which is highly demanded in the cosmetic industry. Addition of an N-terminal honeybee melittin signal peptide for secretion of the produced protein into the (protein-free) medium, as well as a cleavable His-tag at the C-terminus, was crucial for increasing the yield of pure protein. We have successfully crystallized two TYR variants, in both glycosylated and deglycosylated forms, showing preliminary X-ray diffraction patterns at 3.5 Å resolution. Hence, we have established an expression and purification protocol suitable for the crystal structure determination of human TYR, which will give unique atomic insight into the nature and conformation of the residues that shape the substrate binding pocket that will ultimately lead to efficient compound design.
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Affiliation(s)
- Xuelei Lai
- Laboratory of Biophysical Chemistry, University of Groningen, Groningen, The Netherlands
- ESRF-The European Synchrotron, Grenoble, France
| | | | - Harry J. Wichers
- Laboratory of Food Chemistry, Wageningen University, Wageningen, The Netherlands
| | - Bauke W. Dijkstra
- Laboratory of Biophysical Chemistry, University of Groningen, Groningen, The Netherlands
- * E-mail:
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Jagirdar K, Smit DJ, Ainger SA, Lee KJ, Brown DL, Chapman B, Zhen Zhao Z, Montgomery GW, Martin NG, Stow JL, Duffy DL, Sturm RA. Molecular analysis of common polymorphisms within the human Tyrosinase locus and genetic association with pigmentation traits. Pigment Cell Melanoma Res 2014; 27:552-64. [PMID: 24739399 DOI: 10.1111/pcmr.12253] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 04/14/2014] [Indexed: 01/13/2023]
Abstract
We have compared the melanogenic activities of cultured melanocytes carrying two common TYR alleles as homozygous 192S-402R wild-type, heterozygous and homozygous variant. This includes assays of TYR protein, DOPAoxidase activity, glycosylation and temperature sensitivity of protein and DOPAoxidase levels. Homozygous wild-type strains on average had higher levels of TYR protein and enzyme activity than other genotypes. Homozygous 402Q/Q melanocytes produced significantly less TYR protein, displayed altered trafficking and glycosylation, with reduced DOPAoxidase. However, near wild-type TYR activity levels could be recovered at lower growth temperature. In a sample population from Southeast Queensland, these two polymorphisms were present on four TYR haplotypes, designated as WT 192S-402R, 192Y-402R and 192S-402Q with a double-variant 192Y-402Q of low frequency at 1.9%. Based on cell culture findings and haplotype associations, we have used an additive model to assess the penetrance of the ten possible TYR genotypes derived from the combination of these haplotypes.
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Affiliation(s)
- Kasturee Jagirdar
- Institute for Molecular Bioscience, University of Queensland, Brisbane, Qld, Australia
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Rooryck C, Morice F, Lacombe D, Taieb A, Arveiler B. Genetic basis of oculocutaneous albinism. ACTA ACUST UNITED AC 2014. [DOI: 10.1586/edm.09.53] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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17
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Jaworek TJ, Kausar T, Bell SM, Tariq N, Maqsood MI, Sohail A, Ali M, Iqbal F, Rasool S, Riazuddin S, Shaikh RS, Ahmed ZM. Molecular genetic studies and delineation of the oculocutaneous albinism phenotype in the Pakistani population. Orphanet J Rare Dis 2012; 7:44. [PMID: 22734612 PMCID: PMC3537634 DOI: 10.1186/1750-1172-7-44] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 04/30/2012] [Indexed: 02/01/2023] Open
Abstract
Background Oculocutaneous albinism (OCA) is caused by a group of genetically heterogeneous inherited defects that result in the loss of pigmentation in the eyes, skin and hair. Mutations in the TYR, OCA2, TYRP1 and SLC45A2 genes have been shown to cause isolated OCA. No comprehensive analysis has been conducted to study the spectrum of OCA alleles prevailing in Pakistani albino populations. Methods We enrolled 40 large Pakistani families and screened them for OCA genes and a candidate gene, SLC24A5. Protein function effects were evaluated using in silico prediction algorithms and ex vivo studies in human melanocytes. The effects of splice-site mutations were determined using an exon-trapping assay. Results Screening of the TYR gene revealed four known (p.Arg299His, p.Pro406Leu, p.Gly419Arg, p.Arg278*) and three novel mutations (p.Pro21Leu, p.Cys35Arg, p.Tyr411His) in ten families. Ex vivo studies revealed the retention of an EGFP-tagged mutant (p.Pro21Leu, p.Cys35Arg or p.Tyr411His) tyrosinase in the endoplasmic reticulum (ER) at 37°C, but a significant fraction of p.Cys35Arg and p.Tyr411His left the ER in cells grown at a permissive temperature (31°C). Three novel (p.Asp486Tyr, p.Leu527Arg, c.1045-15 T > G) and two known mutations (p.Pro743Leu, p.Ala787Thr) of OCA2 were found in fourteen families. Exon-trapping assays with a construct containing a novel c.1045-15 T > G mutation revealed an error in splicing. No mutation in TYRP1, SLC45A2, and SLC24A5 was found in the remaining 16 families. Clinical evaluation of the families segregating either TYR or OCA2 mutations showed nystagmus, photophobia, and loss of pigmentation in the skin or hair follicles. Most of the affected individuals had grayish-blue colored eyes. Conclusions Our results show that ten and fourteen families harbored mutations in the TYR and OCA2 genes, respectively. Our findings, along with the results of previous studies, indicate that the p.Cys35Arg, p.Arg278* and p.Gly419Arg alleles of TYR and the p.Asp486Tyr and c.1045-15 T > G alleles of OCA2 are the most common causes of OCA in Pakistani families. To the best of our knowledge, this study represents the first documentation of OCA2 alleles in the Pakistani population. A significant proportion of our cohort did not have mutations in known OCA genes. Overall, our study contributes to the development of genetic testing protocols and genetic counseling for OCA in Pakistani families.
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Affiliation(s)
- Thomas J Jaworek
- Division of Pediatric Ophthalmology, Cincinnati Children's Hospital Research Foundation, Cincinnati, OH 45229, USA
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Gargiulo A, Testa F, Rossi S, Di Iorio V, Fecarotta S, de Berardinis T, Iovine A, Magli A, Signorini S, Fazzi E, Galantuomo MS, Fossarello M, Montefusco S, Ciccodicola A, Neri A, Macaluso C, Simonelli F, Surace EM. Molecular and clinical characterization of albinism in a large cohort of Italian patients. Invest Ophthalmol Vis Sci 2011; 52:1281-9. [PMID: 20861488 DOI: 10.1167/iovs.10-6091] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The purpose of this study was to identify the molecular basis of albinism in a large cohort of Italian patients showing typical ocular landmarks of the disease and to provide a full characterization of the clinical ophthalmic manifestations. METHODS DNA samples from 45 patients with ocular manifestations of albinism were analyzed by direct sequencing analysis of five genes responsible for albinism: TYR, P, TYRP1, SLC45A2 (MATP), and OA1. All patients studied showed a variable degree of skin and hair hypopigmentation. Eighteen patients with distinct mutations in each gene associated with OCA were evaluated by detailed ophthalmic analysis, optical coherence tomography (OCT), and fundus autofluorescence. RESULTS Disease-causing mutations were identified in more than 95% of analyzed patients with OCA (28/45 [62.2%] cases with two or more mutations; 15/45 [33.3%] cases with one mutation). Thirty-five different mutant alleles were identified of which 15 were novel. Mutations in TYR were the most frequent (73.3%), whereas mutations in P occurred more rarely (13.3%) than previously reported. Novel mutations were also identified in rare loci such as TYRP1 and MATP. Mutations in the OA1 gene were not detected. Clinical assessment revealed that patients with iris and macular pigmentation had significantly higher visual acuity than did severe hypopigmented phenotypes. CONCLUSIONS TYR gene mutations represent a relevant cause of oculocutaneous albinism in Italy, whereas mutations in P present a lower frequency than that found in other populations. Clinical analysis revealed that the severity of the ocular manifestations depends on the degree of retinal pigmentation.
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Kondo T, Hearing VJ. Update on the regulation of mammalian melanocyte function and skin pigmentation. EXPERT REVIEW OF DERMATOLOGY 2011; 6:97-108. [PMID: 21572549 PMCID: PMC3093193 DOI: 10.1586/edm.10.70] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Melanogenesis is the unique process of producing pigmented biopolymers that are sequestered within melanosomes, which provides color to the skin, hair and eyes of animals and, in the case of human skin, also protects the underlying tissues from UV damage. We review the current understanding of melanogenesis, focusing on factors important to the biochemistry of pigment synthesis, the biogenesis of melanosomes, signaling pathways and factors that regulate melanogenesis, intramelanosomal pH, transport and transfer of melanosomes, and pigmentary disorders related to the dysfunction of melanosome-related proteins. Although it has been known for some time that many of the factors that affect melanogenesis are derived from keratinocytes, fibroblasts, endothelial cells, hormones, inflammatory cells and nerves, a number of new factors that are involved in that regulation have recently been reported, such as factors that regulate melanosome pH and ion transport.
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Affiliation(s)
- Taisuke Kondo
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Vincent J Hearing
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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Chiaverini C, Charlesworth AV, Youssef M, Cuny JF, Rabia SH, Lacour JP, Meneguzzi G. Inversa Dystrophic Epidermolysis Bullosa Is Caused by Missense Mutations at Specific Positions of the Collagenic Domain of Collagen Type VII. J Invest Dermatol 2010; 130:2508-11. [DOI: 10.1038/jid.2010.159] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Molecular and functional studies of tyrosinase variants among Indian oculocutaneous albinism type 1 patients. J Invest Dermatol 2010; 131:260-2. [PMID: 20861851 DOI: 10.1038/jid.2010.274] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Beaumont KA, Liu YY, Sturm RA. The melanocortin-1 receptor gene polymorphism and association with human skin cancer. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 88:85-153. [PMID: 20374726 DOI: 10.1016/s1877-1173(09)88004-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The melanocortin-1 receptor (MC1R) is a key gene involved in the regulation of melanin synthesis and encodes a G-protein coupled receptor expressed on the surface of the melanocyte in the skin and hair follicles. MC1R activation after ultraviolet radiation exposure results in the production of the dark eumelanin pigment and the tanning process in humans, providing physical protection against DNA damage. The MC1R gene is highly polymorphic in Caucasian populations with a number of MC1R variant alleles associated with red hair, fair skin, freckling, poor tanning, and increased risk of melanoma and nonmelanoma skin cancer. Variant receptors have shown alterations in biochemical function, largely due to intracellular retention or impaired G-protein coupling, but retain some signaling ability. The association of MC1R variant alleles with skin cancer risk remains after correction for pigmentation phenotype, indicating regulation of nonpigmentary pathways. Notably, MC1R activation has been linked to DNA repair and may also contribute to the regulation of immune responses.
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Affiliation(s)
- Kimberley A Beaumont
- Melanogenix Group, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Qld 4072, Australia
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Abstract
The genetic basis of melanoma is complex and has both inherited and acquired components. Different genomic approaches have been used to identify a number of inherited risk factors, which can be stratified by penetrance and prevalence. Rare high-penetrance factors are expressed in familial clustering of melanoma and include mutations in CDKN2A (encoding p16(INK4a) and p14(ARF)) and CDK4. These genes are involved in cell-cycle arrest and melanocyte senescence and are nearly invariably targeted by somatic mutations during melanoma progression. Low-penetrance factors are common in the general population and include single-nucleotide polymorphisms in or near MC1R, ASIP, TYR and TYRP1. These genes are major determinants of hair and skin pigmentation, but their role in melanoma development remains unclear. This review describes the efforts that have led to the current understanding of melanoma susceptibility as the result of complex gene-gene and gene-environment interactions. Despite the significant advances, the majority of familial cases remain unaccounted for.
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Dessinioti C, Stratigos AJ, Rigopoulos D, Katsambas AD. A review of genetic disorders of hypopigmentation: lessons learned from the biology of melanocytes. Exp Dermatol 2009; 18:741-9. [PMID: 19555431 DOI: 10.1111/j.1600-0625.2009.00896.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Inherited diseases of pigmentation were among the first traits studied in humans because of their easy recognition. The discovery of genes that regulate melanocytic development and function and the identification of disease-causative mutations have greatly improved our understanding of the molecular basis of pigmentary genodermatoses and their underlying pathogenetic mechanisms. Pigmentation mutants can account for hypo-/amelanosis, with or without altered melanocyte number, resulting in different phenotypes, such as Waardenburg syndrome, piebaldism, Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, oculocutaneous albinism and Griscelli syndrome. In this review, we summarize the basic concepts of melanocyte biology and discuss how molecular defects in melanocyte development and function can result in the development of hypopigmentary hereditary skin diseases.
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Affiliation(s)
- Clio Dessinioti
- Department of Dermatology, A. Sygros Hospital, University of Athens, Athens, Greece
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Giebel LB, Spritz RA. The molecular basis of type I (tyrosinase-deficient) human oculocutaneous albinism. PIGMENT CELL RESEARCH 2008; Suppl 2:101-6. [PMID: 1409411 DOI: 10.1111/j.1600-0749.1990.tb00357.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- L B Giebel
- Department of Medical Genetics, University of Wisconsin, Madison 53706
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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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27
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ASIP and TYR pigmentation variants associate with cutaneous melanoma and basal cell carcinoma. Nat Genet 2008; 40:886-91. [PMID: 18488027 DOI: 10.1038/ng.161] [Citation(s) in RCA: 239] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Accepted: 04/23/2008] [Indexed: 11/08/2022]
Abstract
Fair color increases risk of cutaneous melanoma (CM) and basal cell carcinoma (BCC). Recent genome-wide association studies have identified variants affecting hair, eye and skin pigmentation in Europeans. Here, we assess the effect of these variants on risk of CM and BCC in European populations comprising 2,121 individuals with CM, 2,163 individuals with BCC and over 40,000 controls. A haplotype near ASIP, known to affect a similar spectrum of pigmentation traits as MC1R variants, conferred significant risk of CM (odds ratio (OR) = 1.45, P = 1.2 x 10(-9)) and BCC (OR = 1.33, P = 1.2 x 10(-6)). The variant in TYR encoding the R402Q amino acid substitution, previously shown to affect eye color and tanning response, conferred risk of CM (OR = 1.21, P = 2.8 x 10(-7)) and BCC (OR = 1.14, P = 6.1 x 10(-4)). An eye color variant in TYRP1 was associated with risk of CM (OR = 1.15, P = 4.6 x 10(-4)). The association of all three variants is robust with respect to adjustment for the effect of pigmentation.
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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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Florell SR, Meyer LJ, Boucher KM, Hart M, Cannon-Albright LA, Harris RM, Grossman D, Samlowski WE, Zone JJ, Brinton JP, Leachman SA. Nevus Distribution in a Utah Melanoma Kindred with a Temperature-Sensitive CDKN2A Mutation. J Invest Dermatol 2005; 125:1310-2. [PMID: 16354203 DOI: 10.1111/j.0022-202x.2005.23945.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Gilbert SF. Mechanisms for the environmental regulation of gene expression: ecological aspects of animal development. J Biosci 2005; 30:65-74. [PMID: 15824442 DOI: 10.1007/bf02705151] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The environment can play a significant role in the production of phenotypes. However, the developmental mechanisms by which the environmental agents effect normal development are just becoming known. At least three paths have been found through which the environment can modify gene activity. The first is the neuroendocrine route. Here, the nervous system monitors the environment and transfers signals to the endocrine system. The endocrine hormones can then alter gene expression. The second route involves environmental factors that change the methylation pattern of genes, thereby altering their transcriptional capabilities. The third route involves the direct induction of gene expression in the host by microbial symbionts. The normal regulation of phenotype production by the environment should be considered a normal component of development and developmental biology.
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Affiliation(s)
- Scott F Gilbert
- Department of Biology, Swarthmore College, 500 College Avenue, Swarthmore, PA 19081 USA.
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31
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Schmidt-Küntzel A, Eizirik E, O'Brien SJ, Menotti-Raymond M. Tyrosinase and tyrosinase related protein 1 alleles specify domestic cat coat color phenotypes of the albino and brown loci. ACTA ACUST UNITED AC 2005; 96:289-301. [PMID: 15858157 DOI: 10.1093/jhered/esi066] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The genes encoding enzymes of the tyrosinase family are strong candidates for coat color variation in mammals. To investigate their influence in domestic cat coat color, we determined the complete nucleotide coding sequence of the domestic cat genes tyrosinase (TYR)--a plausible candidate gene for the albino (C) locus, and tyrosinase related protein 1 (TYRP1)--a candidate gene for the brown (B) locus. Sequence variants between individuals exhibiting variation in pigmentation were submitted to association studies. In TYR, two nonsynonymous substitutions encoding TYR-G301R and TYR-G227W were associated with the siamese and burmese phenotypes of the albino locus, respectively. TYRP1 was mapped on chromosome D4 within 5 cM of a highly polymorphic microsatellite, previously found to be fixed in a cat breed selected for the chocolate (b) allele of the B locus, which reinforced TYRP1 as a candidate gene for the B locus in the domestic cat. Two DNA polymorphisms, one leading to a TYRP1-A3G substitution in the signal peptide and another to an in-frame insertion TYRP1-421ins17/18 caused by a donor splice site mutation in intron 6, were associated with the chocolate (b) allele. A premature UAG stop codon at position 100 of TYRP1 was associated with a second allele of the B locus, cinnamon (b(l)). The results provide very strong evidence that the specific nucleotide variants of feline TYR (chromosome D1) are causative of the siamese (c(s)) and burmese (c(b)) alleles of the albino locus, as well as nucleotide variants of TYRP1 (chromosome D4) as specifying the chocolate (b) and cinnamon (b(l)) alleles of the B locus.
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Affiliation(s)
- A Schmidt-Küntzel
- Basic Research Program, SAIC-Frederick, NCI Frederick, Frederick, MD 21702, USA.
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Tomita Y, Suzuki T. Genetics of pigmentary disorders. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2005; 131C:75-81. [PMID: 15452859 DOI: 10.1002/ajmg.c.30036] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The genetic and molecular bases of various types of congenital pigmentary disorders have been classified in the past 10 years, as follows: (1) disorders of melanoblast migration in the embryo from the neural crest to the skin: piebaldism; Waardenburg syndrome 1-4 (WS1-WS4); dyschromatosis symmetrica hereditaria. (2) Disorders of melanosome formation in the melanocyte: Hermansky-Pudlak syndrome 1-7 (HPS1-7); Chediak-Higashi syndrome 1 (CHS1). (3) Disorders of melanin synthesis in the melanosome: oculocutaneous albinism 1-4 (OCA1-4). (4) Disorders of mature melanosome transfer to the tips of the dendrites Griscelli syndrome 1-3 (GS1-3). These disorders are presented and their gene mutations and pathogenesis are discussed.
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Affiliation(s)
- Yasushi Tomita
- Department of Dermatology, Nagoya University Graduate School of Medicine, Showa-ku, Japan.
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Abstract
The environment can play a significant role in the production of phenotypes. However, the developmental mechanisms by which the environment can affect normal development are only now being elucidated. At least three paths have been found through which the environment can modify gene expression. The first is the neuroendocrine route, wherein the nervous system transmits signals from the environment to the endocrine system and the hormones alter gene expression. The second pathway involves environmental agents that change the methylation pattern of genes, thereby altering their transcriptional capacities. The third route involves the direct induction of gene expression in the host by its microbial symbionts. The normal environmental regulation of phenotype production should be considered a normal component of development and developmental biology.
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Affiliation(s)
- Scott F Gilbert
- Department of Biology, Swarthmore College, Swarthmore, Pennsylvania 19081, USA.
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34
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Abstract
Over the past decade, there has been an exponential increase in our knowledge of heritable eye conditions. Coincidentally, our ability to provide accurate genetic diagnoses has allowed appropriate counseling to patients and families. A summary of our current understanding of ocular genetics will prove useful to clinicians, researchers, and students as an introduction to the subject.
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Affiliation(s)
- Ian M MacDonald
- Department of Ophthalmology, University of Alberta, Edmonton, Alberta, Canada
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Suzuki T, Miyamura Y, Inagaki K, Tomita Y. Characterization of the human RAB38 and RAB7 genes: exclusion of new major pathological loci for Japanese OCA. J Dermatol Sci 2003; 32:131-6. [PMID: 12850305 DOI: 10.1016/s0923-1811(03)00071-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Oculocutaneous albinisms (OCAs) are due to various gene mutations that cause a disruption of melanogenesis in the melanocyte. Four different genes associated with human OCA have been reported, however, not all of OCA patients can be classified according to these four genes. We have sought to find a new major locus for Japanese OCA. Recently two genes, RAB38 and RAB7, were reported to play an important role in melanogenesis in the melanocyte, suggesting that these two genes could be good candidates for new OCA loci. OBJECTIVE To determine the structures of the human RAB38 and RAB7 genes, and examine if the two genes are new major loci for Japanese OCA. METHODS We screened mutations in these genes of 25 Japanese OCA patients who lacked mutations in the OCA1 and OCA2 genes with SSCP/heteroduplexes method. RESULTS We determined the both genes, and their genomic organizations to design the primers for SSCP/heteroduplexes method. And then we screened mutations, but no mutation was detected. CONCLUSION Neither of the genes is a new major locus for Japanese OCA.
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Affiliation(s)
- Tamio Suzuki
- Department of Dermatology, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, 466-8550, Nagoya, Japan.
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Oetting WS, Fryer JP, Shriram S, King RA. Oculocutaneous albinism type 1: the last 100 years. PIGMENT CELL RESEARCH 2003; 16:307-11. [PMID: 12753405 DOI: 10.1034/j.1600-0749.2003.00045.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Research on human albinism has been central to many of the major discoveries in human genetics. These include the first evidence that Mendel's rules of genetic segregation apply to humans, first published in 1903. Contrary to initial thought that albinism is caused by mutations in a single gene, we now know that the genetics of albinism are complex. The complexity of albinism was hinted at, in early publications, but has only recently been fully appreciated with the advent of molecular techniques. Currently, 12 different genes have been identified, that when mutated, result in a different type of albinism. Oculocutaneous albinism type 1 (OCA1), resulting from mutations of the tyrosinase gene, is genetically and biochemically the best understood type of albinism. Though much of the research in albinism has involved OCA1, there are many unanswered questions about OCA1 and albinism, in general. The next 100 yr should still provide many surprises as did the first 100 yr.
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Affiliation(s)
- William S Oetting
- Department of Medicine, University of Minnesota, Minneapolis, MN, USA.
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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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Toyofuku K, Wada I, Spritz RA, Hearing VJ. The molecular basis of oculocutaneous albinism type 1 (OCA1): sorting failure and degradation of mutant tyrosinases results in a lack of pigmentation. Biochem J 2001; 355:259-69. [PMID: 11284711 PMCID: PMC1221735 DOI: 10.1042/0264-6021:3550259] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Oculocutaneous albinism type 1 (OCA1) is an autosomal recessive disease resulting from mutations of the tyrosinase gene (TYR). To elucidate the molecular basis of OCA1 phenotypes, we analysed the early processing and maturation of several different types of mutant tyrosinase with various degrees of structural abnormalities (i.e. two large deletion mutants, two missense mutants that completely destroy catalytic function and three missense mutants that have a temperature-sensitive phenotype). When expressed in COS7 cells, all mutant tyrosinases were sensitive to endoglycosidase H digestion, and immunostaining showed their localization in the endoplasmic reticulum (ER) and their failure to be sorted further to their target organelles. Pulse-chase experiments showed that all mutant tyrosinases were retained by calnexin in the ER and that they were degraded at similarly rapid rates, which coincided with their dissociation from calnexin. Temperature-sensitive mutant enzymes were sorted more efficiently at 31 degrees C than at 37 degrees C, and their degradation was accelerated at 37 degrees C compared with 31 degrees C. Thus in contrast to the current concept that mutant tyrosinases are transported to melanosomes but are functionally inactive there, our results suggest that mutant tyrosinases may not be transported to melanosomes in the first place. We conclude that a significant component of mutant tyrosinase malfunction in OCA1 results from their retention and degradation in the ER compartment. This quality-control process is highly sensitive to minimal changes in protein folding, and so even relatively minor mutations in peripheral sequences of the enzyme not involved with catalytic activity may result in a significant reduction of functional enzyme in melanosomes.
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Affiliation(s)
- K Toyofuku
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Building 37, Room 1B25, Bethesda, MD 20892, USA
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Berson JF, Frank DW, Calvo PA, Bieler BM, Marks MS. A common temperature-sensitive allelic form of human tyrosinase is retained in the endoplasmic reticulum at the nonpermissive temperature. J Biol Chem 2000; 275:12281-9. [PMID: 10766867 DOI: 10.1074/jbc.275.16.12281] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Oculocutaneous albinism type 1TS is caused by mutations that render the melanocyte-specific enzyme tyrosinase temperature-sensitive (ts); the enzyme is inactive in cells grown at 37 degrees C but displays full activity in cells grown at 31 degrees C. To distinguish whether the ts phenotype of the common R402Q variant of human tyrosinase is due to altered enzymatic activity or to misfolding and a defect in intracellular trafficking, we analyzed its localization and processing in transiently transfected HeLa cells. R402Q tyrosinase accumulates in the endoplasmic reticulum (ER) at 37 degrees C but exits the ER and accumulates in endosomal structures in cells grown at 31 degrees C. The inability of the R402Q variant to exit the ER is confirmed by the failure to acquire endoglycosidase H resistance at 37 degrees C and cannot be accounted for solely by enhanced proteasome-mediated degradation. ER retention at 37 degrees C is mediated by the lumenal domain of R402Q tyrosinase, is not dependent on tethering to the membrane, and is irreversible. Finally, a wild-type allelic form of tyrosinase is partially ts in transiently transfected HeLa cells. The data show that human tyrosinase expressed in non-melanogenic cells folds and exits the ER inefficiently and that R402Q tyrosinase exaggerates this defect, resulting in a failure to exit the ER at physiologic temperatures.
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Affiliation(s)
- J F Berson
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6082, USA
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Parry D, Peters G. Temperature-sensitive mutants of p16CDKN2 associated with familial melanoma. Mol Cell Biol 1996; 16:3844-52. [PMID: 8668202 PMCID: PMC231381 DOI: 10.1128/mcb.16.7.3844] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Altered expression or function of the p16CDKN2 tumor suppressor gene on chromosome 9p21 occurs in a wide range of human tumors, and mutations in the gene have been shown to segregate with familial predisposition to malignant melanoma. We have used a variety of assays to examine the functional properties of tumor-associated alleles, including eight premature termination mutants, eight missense mutants, and three isoforms of p16 initiated at different amino-terminal methionine codons. The amino- and carboxy-terminal domains of the protein, outside the ankyrin-like repeats, appeared to be dispensable, but the majority of the premature termination mutations led to loss of function. Of the missense mutations tested, four displayed clear loss of function whereas two behaved like the wild type under all conditions tested. The remaining two mutations, a G-to-W mutation at position 101 (Gl01W) and V126D, both of which are associated with familial melanoma, were found to be temperature sensitive for binding to Cdk4 and Cdk6 in vitro, for inhibiting cyclin D1-Cdk4 in a reconstituted pRb-kinase assay, and for increasing the proportion of G1-phase cells following transfection. These findings clarify previous disparities and argue strongly that p16CDKN2 is a bona fide tumor suppressor associated with familial melanoma.
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Affiliation(s)
- D Parry
- Imperial Cancer Research Fund Laboratories, London, United Kingdom
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Summers CG. Vision in albinism. TRANSACTIONS OF THE AMERICAN OPHTHALMOLOGICAL SOCIETY 1996; 94:1095-155. [PMID: 8981720 PMCID: PMC1312119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
PURPOSE The purpose of this investigation was to study vision in albinism from 3 perspectives: first, to determine the characteristics of grating acuity development in children with albinism; second, to study the effect of illumination on grating acuity; and third, to define the effect of melanin pigment in the macula on visual acuity. METHODS I. Binocular and monocular grating acuity was measured with the acuity card procedure in 40 children with albinism during the first 3 years of life. Recognition acuity was eventually measured in 27 of these patients. Ocular pigment was documented by a previously established method of grading iris transillumination and macular transparency. II. Grating acuity under standard and increased illumination levels was measured in 20 adults with albinism (group I) compared with that in 20 adults with nystagmus due to conditions other than albinism (group II) and 20 adults without ocular abnormalities (group III). Recognition acuity measured with the ETDRS charts was also recorded for each group. III. Best-corrected binocular acuity was measured in 29 patients with albinism who were identified with melanin pigment in their maculas by direct ophthalmoscopy. RESULTS I. Both binocular and monocular grating acuity was reduced 2 to 3 octaves below the norm for ages 6 months to 3 years. Limited data available in the first 6 months of life did not show failure of vision to develop. Grating acuity measurements overestimated eventual recognition acuity. Mean recognition acuity was 20/111. A relationship between grating acuity development and presence or absence of ocular pigment was not found. II. Grating acuity was significantly better for groups I and II under the condition of increased illumination (P < .03). For patients with albinism, grating acuity under standard illumination was significantly better than recognition acuity (P < .001). For all groups, grating acuity under increased illumination was significantly better than recognition acuity (P < .01). III. Mean recognition acuity in patients with albinism and melanin pigment in their maculas (20/47) was significantly better than measured recognition acuity in Project I (P < .001). All had foveal hypoplasia, but 8 patients had an incompletely developed annular reflex in the macula, 6 patients showed stereoacuity, and 3 patients had no nystagmus. CONCLUSIONS I. Grating acuity development in albinism seems to progress along a curve that is asymptotic to visual development in a normal population. II. Increasing illumination does not reduce grating acuity in patients with albinism. Grating acuity overestimates recognition acuity in these patients. III. Ophthalmoscopic detection of melanin pigment in the macula in patients with albinism is associated with better vision.
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Vijayasaradhi S, Houghton AN. Melanoma and melanocytes: pigmentation, tumor progression, and the immune response to cancer. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1995; 32:343-74. [PMID: 7748799 DOI: 10.1016/s1054-3589(08)61017-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- S Vijayasaradhi
- Memorial Sloan-Kettering Cancer Center, New York, New York 10021, 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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Orlow SJ, Lamoreux ML, Pifko-Hirst S, Zhou BK. Pathogenesis of the platinum (cp) mutation, a model for oculocutaneous albinism. J Invest Dermatol 1993; 101:137-40. [PMID: 7688401 DOI: 10.1111/1523-1747.ep12363621] [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: 01/26/2023]
Abstract
The platinum mutation at the C (albino) locus in the mouse is a potential model for oculocutaneous albinism in humans other than type IA (tyrosinase-negative) albinism. Although tissues from mice homozygous for the mutation display substantial tyrosinase activity, cutaneous and ocular pigmentation is severely restricted in affected animals. Using specific antipeptide antisera, we demonstrate that ocular extracts from wild-type mice contain two isoforms of tyrosinase bearing either the amino-terminal PEP5 epitope or the carboxy-terminal PEP7 epitope. The latter isoform participates in a high-molecular-weight complex detectable on sucrose density gradients. In platinum mice, antiserum to the PEP7 epitope fails to recognize any protein species, and the high-molecular-weight form of tyrosinase is not detectable. Our results support a key role for this high-molecular-weight complex in melanogenesis, and suggest that mutations that interfere with the ability of tyrosinase to participate in a multimeric complex may be a cause of oculocutaneous albinism in people.
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Affiliation(s)
- S J Orlow
- Ronald O. Perelman Department of Dermatology, New York University School of Medicine, NY 10016
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Ito S. High-Performance Liquid Chromatography (HPLC) Analysis of Eu- and Pheomelanin in Melanogenesis Control. J Invest Dermatol 1993. [DOI: 10.1111/1523-1747.ep12465109] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Ito S. High-Performance Liquid Chromatography (HPLC) Analysis of Eu- and Pheomelanin in Melanogenesis Control. J Invest Dermatol 1993. [DOI: 10.1038/jid.1993.71] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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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