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Kuht HJ, Thomas MG, McLean RJ, Sheth V, Proudlock FA, Gottlob I. Abnormal foveal morphology in carriers of oculocutaneous albinism. Br J Ophthalmol 2023; 107:1202-1208. [PMID: 35379600 PMCID: PMC10359511 DOI: 10.1136/bjophthalmol-2020-318192] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 03/18/2022] [Indexed: 01/04/2023]
Abstract
BACKGROUND/AIMS To investigate the foveal morphology in carriers of oculocutaneous albinism (OCA) using spectral domain optical coherence tomography (SD-OCT). A cross-sectional, observational study. METHODS Handheld SD-OCT (Envisu C2300) was used to acquire horizontal scans through the centre of the fovea in biological parents of patients with OCA (n=28; mean age±SD=40.43±8.07 years) and age-matched and ethnicity-matched controls (n=28; mean age±SD=38.04±10.27 years). Sequence analysis was performed for variants in known genes associated with OCA. Best-corrected visual acuity (BCVA), presence of foveal hypoplasia and grade, foveal, parafoveal and perifoveal thickness measurements of total retinal layers (TRL), inner retinal layers (IRL) and outer retinal layers (ORL) thickness were measured. RESULTS Foveal hypoplasia was identified in 32.14% of OCA carriers; grade 1 in all cases. OCA carriers demonstrated significant thicker TRL thickness (median difference: 13.46 µm, p=0.009) and IRL thickness (mean difference: 8.98 µm, p<0.001) at the central fovea compared with controls. BCVA of carriers was between -0.16 and 0.18 logMAR (mean: 0.0 logMAR). No significant differences in BCVA was noted between OCA carriers or controls (p=0.83). In the OCA carriers, we identified previously reported pathogenic variants in TYR, OCA2 and SLC45A2, novel OCA2 variants (n=3) and heterozygosity of the pathogenic TYR haplotype. CONCLUSION We have, for the first time, identified foveal abnormalities in OCA carriers. This provides clinical value, particularly in cases where limited phenotype data are available. Our findings raise the possibility that previously reported mild cases of foveal hypoplasia or isolated foveal hypoplasia could correspond to OCA carrier status.
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Affiliation(s)
- Helen J Kuht
- Ulverscroft Eye Unit, Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Mervyn G Thomas
- Ulverscroft Eye Unit, Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Rebecca J McLean
- Ulverscroft Eye Unit, Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Viral Sheth
- Ulverscroft Eye Unit, Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Frank A Proudlock
- Ulverscroft Eye Unit, Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
| | - Irene Gottlob
- Ulverscroft Eye Unit, Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, UK
- Cooper Medical School of Rowan University, Cooper Neurological Institute, Camden, New Jersey, USA
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2
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Arcadepani FB, Gadelha A, Margolis RL. Mutation of GPR143 Associated With Ocular Albinism Type 1, Intellectual Disability, and Schizophrenia: The Complex Biological and Social Interactions Between Genetic Syndromes and Mental Illness. J Psychiatr Pract 2023; 29:77-81. [PMID: 36649556 DOI: 10.1097/pra.0000000000000685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Copy number variations, which manifest primarily as deletions and duplications, contribute significantly to the genetic risk of schizophrenia. Specific syndromes associated with copy number variations, exemplified by the 22q11 deletion syndrome, confer both congenital abnormalities and an elevated risk of schizophrenia. We report the case of a patient with a deletion of exons 2 through 8 of GPR143. In addition to having the ophthalmologic disorder ocular albinism type 1 (OA1), a well-established consequence of mutations of GPR143, the patient is also intellectually impaired and impulsive, and he developed schizophrenia at age 15. Psychiatric manifestations of OA1 have not previously been reported, yet remain plausible, as the GPR143 protein is widely distributed in the brain and may function as an L-DOPA receptor. However, the patient described here also had a family history of psychiatric disorders independent of OA1, in utero exposure to heroin and cocaine, and challenging family circumstances. We suggest that the relationship between his GPR143 mutation and his psychiatric disorders is complex. The mutation may have directly contributed to his cognitive and psychiatric disorders, but we also suspect that OA1, present in multiple family members, contributed to multigenerational familial instability. Further, OA1 likely exacerbated our patient's cognitive and social impairment by interfering with his education, while his neuropsychiatric status frequently interfered with the assessment and treatment of his OA1. We conclude that the psychiatric and nonpsychiatric manifestations of a genetic syndrome are best managed in parallel and that psychiatrists and other mental health providers may be in the best position to assure that patients receive appropriate genetic and medical care.
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3
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Torriano S, Baulier E, Garcia Diaz A, Corneo B, Farber DB. CRISPR-AsCas12a Efficiently Corrects a GPR143 Intronic Mutation in Induced Pluripotent Stem Cells from an Ocular Albinism Patient. CRISPR J 2022; 5:457-471. [PMID: 35686978 PMCID: PMC9233509 DOI: 10.1089/crispr.2021.0110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Mutations in the GPR143 gene cause X-linked ocular albinism type 1 (OA1), a disease that severely impairs vision. We recently generated induced pluripotent stem cells (iPSCs) from skin fibroblasts of an OA1 patient carrying a point mutation in intron 7 of GPR143. This mutation activates a new splice site causing the incorporation of a pseudoexon. In this study, we present a high-performance CRISPR-Cas ribonucleoprotein strategy to permanently correct the GPR143 mutation in these patient-derived iPSCs. Interestingly, the two single-guide RNAs available for SpCas9 did not allow the cleavage of the target region. In contrast, the cleavage achieved with the CRISPR-AsCas12a system promoted homology-directed repair at a high rate. The CRISPR-AsCas12a-mediated correction did not alter iPSC pluripotency or genetic stability, nor did it result in off-target events. Moreover, we highlight that the disruption of the pathological splice site caused by CRISPR-AsCas12a-mediated insertions/deletions also rescued the normal splicing of GPR143 and its expression level.
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Affiliation(s)
- Simona Torriano
- Department of Ophthalmology, UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, California, USA
| | - Edouard Baulier
- Department of Ophthalmology, UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, California, USA
| | - Alejandro Garcia Diaz
- Stem Cell Core, Columbia Stem Cell Initiative, Columbia University Irving Medical Center, New York, New York, USA
| | - Barbara Corneo
- Stem Cell Core, Columbia Stem Cell Initiative, Columbia University Irving Medical Center, New York, New York, USA
| | - Debora B Farber
- Department of Ophthalmology, UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, California, USA.,Molecular Biology Institute and UCLA, Los Angeles, California, USA.,Brain Research Institute, UCLA, Los Angeles, California, USA
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4
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Galli J, Loi E, Morandi A, Scaglioni V, Rossi A, Molinaro A, Pasini N, Semeraro F, Ruberto G, Fazzi E. Neurodevelopmental Profile in Children Affected by Ocular Albinism. Neuropediatrics 2022; 53:7-14. [PMID: 34327695 DOI: 10.1055/s-0041-1732430] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
AIM The aim of this study was to detail the neurodevelopmental profile of subjects affected by ocular albinism (OA) and to collect data on GPR143 gene analysis. DESIGN The design of the study involves a retrospective longitudinal observational case series. METHODS We collected data on the neurodevelopmental profile of 13 children affected by OA from clinical annual assessments conducted for a period of 6 years after the first evaluation. We described visual profile, neuromotor development and neurological examination, cognitive profile, communication and language skills and behavioral characteristics. The GPR143 gene analysis was performed as well. RESULTS Children presented a variable combination of ocular and oculomotor disorders unchanged during the follow-up, a deficit in visual acuity and in contrast sensitivity that progressively improved. Abnormalities in pattern visual evoked potential were found. No deficits were detected at neurological examination and neuromotor development except for a mild impairment in hand-eye coordination observed in five cases. A language delay was observed in five cases, two of whom had also a developmental quotient delay at 2 years evolving to a borderline/deficit cognitive level at preschool age, difficulties in adaptive behavior and autistic-like features were found. Mutations in the GPR143 gene were identified in the two patients who presented the most severe clinical phenotype. CONCLUSION Children with OA may share, in addition to a variable combination of ocular signs and symptoms, a neurodevelopment impairment regarding mostly the cognitive, communicative, and social area, especially those with GPR143 mutation.
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Affiliation(s)
- Jessica Galli
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.,Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Erika Loi
- Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy.,Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Alessandra Morandi
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.,Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Vera Scaglioni
- Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Andrea Rossi
- Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Anna Molinaro
- Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Nadia Pasini
- Department of Neurological and Vision Sciences, ASST Spedali Civili of Brescia, Eye Clinic, Brescia, Italy
| | - Francesco Semeraro
- Department of Neurological and Vision Sciences, ASST Spedali Civili of Brescia and University of Brescia, Eye Clinic, Brescia, Italy
| | - Giulio Ruberto
- Department of Surgical and Clinical, Diagnostic and Pediatric Sciences, Section of Ophthalmology, Univeristy of Pavia, IRCCS Fondazione Policlinico San Matteo, Pavia, Italy
| | - Elisa Fazzi
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy.,Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
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5
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Zhong J, You B, Xu K, Zhang X, Xie Y, Li Y. GPR143 genotypic and ocular phenotypic characterisation in a Chinese cohort with ocular albinism. Ophthalmic Genet 2021; 42:717-724. [PMID: 34346269 DOI: 10.1080/13816810.2021.1958352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE Ocular albinism type I (OA1) is caused by mutations in the GPR143 gene. The purpose of this study was to describe the clinical and genetic findings in 13 patients from 12 unrelated Chinese pedigrees with a pathogenic variant of the GPR143 gene. METHODS Most patients underwent clinical examination, including best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, fundus examination, spectral domain optical coherence tomography, and full-field electroretinograms (ERG). A combination of molecular screening procedures, consisting of Sanger-DNA sequencing of GPR143 and targeted next-generation sequencing, was performed to identify each mutation. In silico programs were utilized to evaluate the pathogenicity of all the variants. RESULTS The 13 patients (mean age 21.75 ± 16.63 years, range 1-54 years) all presented with congenital nystagmus, different extents of visual impairment, and severe foveal hypoplasia. Their BCVA was between 0.05 and 0.3 (decimal notation). The patients and obligate carriers exhibited different extents of mild depigmentation of the iris and fundus. We detected 11 distinct mutations in this patient cohort, including 7 novel mutations. Most (82%) were null mutations and included frameshift indel, nonsense, splicing effect, and large genomic DNA deletions, while missense mutations only accounted for 18%. CONCLUSIONS Patients with GPR143 mutations all have congenital nystagmus, visual impairment, and foveal hypoplasia, whereas hypopigmentation in their iris and fundus is mild. They exhibit no evident genotype-phenotype correlations. GPR143 mutation screening is very important for establishing a precise diagnosis and for providing genetic counseling for patients and their families.
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Affiliation(s)
- Junwei Zhong
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
| | - Bing You
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
| | - Ke Xu
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
| | - Xiaohui Zhang
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
| | - Yue Xie
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
| | - Yang Li
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing, China
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6
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McKay BS. Pigmentation and vision: Is GPR143 in control? J Neurosci Res 2019; 97:77-87. [PMID: 29761529 PMCID: PMC6235735 DOI: 10.1002/jnr.24246] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/21/2018] [Accepted: 03/21/2018] [Indexed: 12/30/2022]
Abstract
Albinism, typically characterized by decreased melanin synthesis, is associated with significant visual deficits owing to developmental changes during neurosensory retina development. All albinism is caused by genetic mutations in a group of diverse genes including enzymes, transporters, G-protein coupled receptor. Interestingly, these genes are not expressed in the neurosensory retina. Further, regardless of cause of albinism, all forms of albinism have the same retinal pathology, the extent of which is variable. In this review, we explore the possibility that this similarity in retinal phenotype is because all forms of albinism funnel through the same final common pathway. There are currently seven known genes linked to the seven forms of ocular cutaneous albinism. These types of albinism are the most common, and result in changes to all pigmented tissues (hair, skin, eyes). We will discuss the incidence and mechanism, where known, to develop a picture as to how the mutations cause albinism. Next, we will examine the one form of albinism which causes tissue-specific pathology, ocular albinism, where the eye exhibits the retinal albinism phenotype despite near normal melanin synthesis. We will discuss a potential way to treat the disease and restore normal retinal development. Finally, we will briefly discuss the possibility that this same pathway may intersect with the most common cause of permanent vision loss in the elderly.
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Affiliation(s)
- Brian S McKay
- Department of Ophthalmology and Vision Science, University of Arizona, Tucson, Arizona
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7
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Identification of a novel GPR143 mutation in X-linked ocular albinism with marked intrafamilial phenotypic variability. J Genet 2018. [DOI: 10.1007/s12041-018-1024-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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9
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Liu J, Jia Y, Wang L, Bu J. A previously unidentified deletion in G protein-coupled receptor 143 causing X-linked congenital nystagmus in a Chinese family. Indian J Ophthalmol 2017; 64:813-817. [PMID: 27958203 PMCID: PMC5200982 DOI: 10.4103/0301-4738.195593] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Background: Congenital nystagmus (CN) is characterized by conjugated, spontaneous, and involuntary ocular oscillations. It is an inherited disease and the most common inheritance pattern is X-linked CN. In this study, our aim is to identify the disease-causing mutation in a large sixth-generation Chinese family with X-linked CN. Methods: It has been reported that mutations in four-point-one, ezrin, radixin, moesin domain-containing 7 gene (FRMD7) and G protein-coupled receptor 143 gene (GPR143) account for the majority patients of X-linked nystagmus. We collected 8 ml blood samples from members of a large sixth-generation pedigree with X-linked CN and 100 normal controls. FRMD7 and GPR143 were scanned by polymerase chain reaction (PCR)-based DNA sequencing assays, and multiplex PCR assays were applied to detect deletions. Results: We identified a previously unreported deletion covering 7 exons in GPR143 in a Chinese family. The heterozygous deletion from exon 3 to exon 9 of GPR143 was detected in all affected males in the family, while it was not detected in other unaffected relatives or 100 normal controls. Conclusions: This is the first report of molecular characterization in GPR143 gene in the CN family. Our results expand the spectrum of GPR143 mutations causing CN and further confirm the role of GPR143 in the pathogenesis of CN.
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Affiliation(s)
- Jing Liu
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing 100191, P. R. China
| | - Yanlei Jia
- Department of ophthalmology, The Municipal Hospital of Zaozhuang, Shandong 277100, P. R. China
| | - Lejin Wang
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing 100191, P. R. China
| | - Juan Bu
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing 100191, P. R. China
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10
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Jia X, Yuan J, Jia X, Ling S, Li S, Guo X. GPR143 mutations in Chinese patients with ocular albinism type 1. Mol Med Rep 2017; 15:3069-3075. [PMID: 28339057 PMCID: PMC5428903 DOI: 10.3892/mmr.2017.6366] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 02/03/2017] [Indexed: 12/23/2022] Open
Abstract
The aim of the present study was to evaluate mutations of the G protein-coupled receptor 143 (GPR143) gene for ocular albinism type 1 (OA1) in Chinese patients. For the current study, 8 patients with OA1 were selected from the database of ocular genetic diseases. Genomic DNA of OA1 was prepared from venous leukocytes collected from the patients. Cycle sequencing was used to analyze the exons and adjacent introns of GPR143. The variation detected was analyzed by bidirectional DNA sequencing and further evaluated in 96 controls using heteroduplex-single strand conformational polymorphism analysis. Additionally, slit lamp photography of anterior segment, fundus photography and optical coherence tomography (OCT) were performed to identify the clinical features of OA1. In five patients with OA1, 5 GPR143 gene mutations were identified and four of them there were novel mutations. The screening rate is 62.5%, including c.333G>A (p.W111X), c.353G>A (p.G118E) (known mutation), C.658+2T>G (splice mutation), c.215_216insCGCTGC (p.71-72insAA) and c.17T>C (p. L6P). These mutations were absent in the 96 normal controls. Only one patient with OA1 in the present study was female. Patients with OA1 often have congenital nystagmus, refractive error, severe decline of visual acuity (from 0.1 to 0.4) and foveal hypoplasia. Different degrees of pigment loss were evident in the patients' iris and retina, whereas macular structure was not identified in the OCT examination. The findings of the present study expanded the gene mutation spectrum of GPR143 and investigated the clinical phenotype of patients with OA1 in the Chinese population. Additional evidence for clinical diagnosis was provided along with differential diagnosis and genetic counseling.
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Affiliation(s)
- Xiuhua Jia
- Department of Ophthalmology, The Third Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510630, P.R. China
| | - Jin Yuan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat‑sen University, Guangzhou, Guangdong 510060, P.R. China
| | - Xiaoyun Jia
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat‑sen University, Guangzhou, Guangdong 510060, P.R. China
| | - Shiqi Ling
- Department of Ophthalmology, The Third Affiliated Hospital, Sun Yat‑sen University, Guangzhou, Guangdong 510630, P.R. China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat‑sen University, Guangzhou, Guangdong 510060, P.R. China
| | - Xiangming Guo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat‑sen University, Guangzhou, Guangdong 510060, P.R. China
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11
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Clinical evaluation and molecular screening of a large consecutive series of albino patients. J Hum Genet 2016; 62:277-290. [PMID: 27734839 DOI: 10.1038/jhg.2016.123] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 09/08/2016] [Accepted: 09/10/2016] [Indexed: 12/26/2022]
Abstract
Oculocutaneous albinism (OCA) is characterized by hypopigmentation of the skin, hair and eye, and by ophthalmologic abnormalities caused by a deficiency in melanin biosynthesis. In this study we recruited 321 albino patients and screened them for the genes known to cause oculocutaneous albinism (OCA1-4 and OCA6) and ocular albinism (OA1). Our purpose was to detect mutations and genetic frequencies of the main causative genes, offering to albino patients an exhaustive diagnostic assessment within a multidisciplinary approach including ophthalmological, dermatological, audiological and genetic evaluations. We report 70 novel mutations and the frequencies of the major causative OCA genes that are as follows: TYR (44%), OCA2 (17%), TYRP1 (1%), SLC45A2 (7%) and SLC24A5 (<0.5%). An additional 5% of patients had GPR143 mutations. In 19% of cases, a second reliable mutation was not detected, whereas 7% of our patients remain still molecularly undiagnosed. This comprehensive study of a consecutive series of OCA/OA1 patients allowed us to perform a clinical evaluation of the different OCA forms.
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12
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Young A, Dandekar U, Pan C, Sader A, Zheng JJ, Lewis RA, Farber DB. GNAI3: Another Candidate Gene to Screen in Persons with Ocular Albinism. PLoS One 2016; 11:e0162273. [PMID: 27607449 PMCID: PMC5015898 DOI: 10.1371/journal.pone.0162273] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 08/21/2016] [Indexed: 11/18/2022] Open
Abstract
Ocular albinism type 1 (OA), caused by mutations in the OA1 gene, encodes a G-protein coupled receptor, OA1, localized in melanosomal membranes of the retinal pigment epithelium (RPE). This disorder is characterized by both RPE macro-melanosomes and abnormal decussation of ganglion cell axons at the brain's optic chiasm. We demonstrated previously that Oa1 specifically activates Gαi3, which also signals in the Oa1 transduction pathway that regulates melanosomal biogenesis. In this study, we screened the human Gαi3 gene, GNAI3, in DNA samples from 26 patients who had all clinical characteristics of OA but in whom a specific mutation in the OA1 gene had not been found, and in 6 normal control individuals. Using the Agilent HaloPlex Target Enrichment System and next-generation sequencing (NGS) on the Illumina MiSeq platform, we identified 518 variants after rigorous filtering. Many of these variants were corroborated by Sanger sequencing. Overall, 98.8% coverage of the GNAI3 gene was obtained by the HaloPlex amplicons. Of all variants, 6 non-synonymous and 3 synonymous were in exons, 41 in a non-coding exon embedded in the 3' untranslated region (UTR), 6 in the 5' UTR, and 462 in introns. These variants included novel SNVs, insertions, deletions, and a frameshift mutation. All were found in at least one patient but none in control samples. Using computational methods, we modeled the GNAI3 protein and its non-synonymous exonic mutations and determined that several of these may be the cause of disease in the patients studied. Thus, we have identified GNAI3 as a second gene possibly responsible for X-linked ocular albinism.
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Affiliation(s)
- Alejandra Young
- Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
- Molecular Biology Institute, UCLA, Los Angeles, CA, United States of America
| | - Uma Dandekar
- UCLA-GenoSeq Core, UCLA, Los Angeles, CA, United States of America
| | - Calvin Pan
- UCLA-GenoSeq Core, UCLA, Los Angeles, CA, United States of America
| | - Avery Sader
- Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
| | - Jie J. Zheng
- Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
| | - Richard A. Lewis
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States of America
| | - Debora B. Farber
- Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
- Molecular Biology Institute, UCLA, Los Angeles, CA, United States of America
- Brain Research Institute, UCLA, Los Angeles, CA, United States of America
- * E-mail:
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Hazlewood RJ, Roos BR, Solivan-Timpe F, Honkanen RA, Jampol LM, Gieser SC, Meyer KJ, Mullins RF, Kuehn MH, Scheetz TE, Kwon YH, Alward WLM, Stone EM, Fingert JH. Heterozygous triplication of upstream regulatory sequences leads to dysregulation of matrix metalloproteinase 19 in patients with cavitary optic disc anomaly. Hum Mutat 2015; 36:369-78. [PMID: 25581579 DOI: 10.1002/humu.22754] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 12/23/2014] [Indexed: 11/06/2022]
Abstract
Patients with a congenital optic nerve disease, cavitary optic disc anomaly (CODA), are born with profound excavation of the optic nerve resembling glaucoma. We previously mapped the gene that causes autosomal-dominant CODA in a large pedigree to a chromosome 12q locus. Using comparative genomic hybridization and quantitative PCR analysis of this pedigree, we report identifying a 6-Kbp heterozygous triplication upstream of the matrix metalloproteinase 19 (MMP19) gene, present in all 17 affected family members and no normal members. Moreover, the triplication was not detected in 78 control subjects or in the Database of Genomic Variants. We further detected the same 6-Kbp triplication in one of 24 unrelated CODA patients and in none of 172 glaucoma patients. Analysis with a Luciferase assay showed that the 6-Kbp sequence has transcription enhancer activity. A 773-bp fragment of the 6-Kbp DNA segment increased downstream gene expression eightfold, suggesting that triplication of this sequence may lead to dysregulation of the downstream gene, MMP19, in CODA patients. Lastly, immunohistochemical analysis of human donor eyes revealed strong expression of MMP19 in optic nerve head. These data strongly suggest that triplication of an enhancer may lead to overexpression of MMP19 in the optic nerve that causes CODA.
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Affiliation(s)
- Ralph J Hazlewood
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, Iowa; Stephen A. Wynn Institute for Vision Research, University of Iowa, Iowa City, Iowa
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14
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Deep intronic GPR143 mutation in a Japanese family with ocular albinism. Sci Rep 2015; 5:11334. [PMID: 26061757 PMCID: PMC4650666 DOI: 10.1038/srep11334] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/21/2015] [Indexed: 11/08/2022] Open
Abstract
Deep intronic mutations are often ignored as possible causes of human disease. Using whole-exome sequencing, we analysed genomic DNAs of a Japanese family with two male siblings affected by ocular albinism and congenital nystagmus. Although mutations or copy number alterations of coding regions were not identified in candidate genes, the novel intronic mutation c.659-131 T > G within GPR143 intron 5 was identified as hemizygous in affected siblings and as heterozygous in the unaffected mother. This mutation was predicted to create a cryptic splice donor site within intron 5 and activate a cryptic acceptor site at 41nt upstream, causing the insertion into the coding sequence of an out-of-frame 41-bp pseudoexon with a premature stop codon in the aberrant transcript, which was confirmed by minigene experiments. This result expands the mutational spectrum of GPR143 and suggests the utility of next-generation sequencing integrated with in silico and experimental analyses for improving the molecular diagnosis of this disease.
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Two novel splicing mutations in the SLC45A2 gene cause Oculocutaneous Albinism Type IV by unmasking cryptic splice sites. J Hum Genet 2015; 60:467-71. [PMID: 26016411 DOI: 10.1038/jhg.2015.56] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 03/30/2015] [Accepted: 04/26/2015] [Indexed: 11/08/2022]
Abstract
Oculocutaneous albinism (OCA) is characterized by hypopigmentation of the skin, hair and eye, and by ophthalmologic abnormalities caused by a deficiency in melanin biosynthesis. OCA type IV (OCA4) is one of the four commonly recognized forms of albinism, and is determined by mutation in the SLC45A2 gene. Here, we investigated the genetic basis of OCA4 in an Italian child. The mutational screening of the SLC45A2 gene identified two novel potentially pathogenic splicing mutations: a synonymous transition (c.888G>A) involving the last nucleotide of exon 3 and a single-nucleotide insertion (c.1156+2dupT) within the consensus sequence of the donor splice site of intron 5. As computer-assisted analysis for mutant splice-site prediction was not conclusive, we investigated the effects on pre-mRNA splicing of these two variants by using an in vitro minigene approach. Production of mutant transcripts in HeLa cells demonstrated that both mutations cause the almost complete abolishment of the physiologic donor splice site, with the concomitant unmasking of cryptic donor splice sites. To our knowledge, this work represents the first in-depth molecular characterization of splicing defects in a OCA4 patient.
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McCafferty BK, Wilk MA, McAllister JT, Stepien KE, Dubis AM, Brilliant MH, Anderson JL, Carroll J, Summers CG. Clinical Insights Into Foveal Morphology in Albinism. J Pediatr Ophthalmol Strabismus 2015; 52:167-72. [PMID: 26053207 PMCID: PMC4948980 DOI: 10.3928/01913913-20150427-06] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2014] [Accepted: 01/13/2015] [Indexed: 11/20/2022]
Abstract
PURPOSE A hallmark of albinism is foveal hypoplasia. However, literature suggests variable foveal development. This study evaluates the association between ocular phenotype and foveal morphology to demonstrate the broad structural and functional spectrum. METHODS Best-corrected visual acuity (BCVA), nystagmus, angle kappa, stereoacuity, iris transillumination, macular melanin presence, foveal avascular zone, and annular reflex were recorded in 14 patients with albinism. Spectral-domain optical coherence tomography provided macular images. RESULTS The clinical phenotype was broad, with BCVA varying from 20/20 to 20/100. Better BCVA was associated with a preserved foveal avascular zone, annular macular reflex, stereoacuity, and macular melanin. Imaging demonstrated a continuum of foveal development correlating with BCVA. Individuals with a rudimentary pit had normal inner and outer segment lengthening and better BCVA. CONCLUSIONS The spectrum of ocular structure and visual function in albinism is broad, suggesting a possible diagnosis of albinism in a patient with an even more normal clinical presentation.
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MESH Headings
- Adolescent
- Adult
- Aged, 80 and over
- Albinism, Ocular/diagnosis
- Albinism, Ocular/genetics
- Albinism, Ocular/physiopathology
- Albinism, Oculocutaneous/diagnosis
- Albinism, Oculocutaneous/genetics
- Albinism, Oculocutaneous/physiopathology
- Child
- DNA Mutational Analysis
- Depth Perception/physiology
- Evoked Potentials, Visual
- Eye Abnormalities/diagnosis
- Eye Abnormalities/genetics
- Eye Abnormalities/physiopathology
- Eye Proteins/genetics
- Female
- Fovea Centralis/abnormalities
- Fovea Centralis/pathology
- Humans
- Male
- Membrane Proteins/genetics
- Nystagmus, Pathologic/diagnosis
- Phenotype
- Polymerase Chain Reaction
- Prospective Studies
- Tomography, Optical Coherence
- Visual Acuity/physiology
- Young Adult
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Li Y, Pu J, Zhang B. Expression of a novel splice variant of FRMD7 in developing human fetal brains that is upregulated upon the differentiation of NT2 cells. Exp Ther Med 2014; 8:1131-1136. [PMID: 25187810 PMCID: PMC4151643 DOI: 10.3892/etm.2014.1916] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2014] [Accepted: 08/04/2014] [Indexed: 12/15/2022] Open
Abstract
FRMD7 mutations are associated with X-linked idiopathic congenital nystagmus (ICN); however, the underlying mechanisms whereby mutations of FRMD7 lead to ICN remain unclear. In a previous study, the first FRMD7 splice variant (FRMD7-S) was cloned and identified, and FRMD7-S was hypothesized to play a significant role in neuronal differentiation and development. The present study investigated a novel multiple exon-skipping mRNA splice variant of FRMD7, termed FRMD7_SV2, which was detected in NT2 cells using northern blotting. The mRNA expression levels of FRMD7_SV2 in the developing human fetal brain were examined using reverse transcription polymerase chain reaction (PCR), while the expression levels in NT2 cells treated with retinoid acid (RA) or bone morphogenetic protein-2 were investigated using quantitative PCR. The results revealed that the expression of FRMD7_SV2 was spatially and temporally restricted in human fetal brain development, and was upregulated upon RA-induced neuronal differentiation of the NT2 cells. These results indicated that as a novel splice variant of FRMD7, FRMD7_SV2 may play a role in neuronal development.
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Affiliation(s)
- Yingzhi Li
- Department of Neurology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Jiali Pu
- Department of Neurology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
| | - Baorong Zhang
- Department of Neurology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310009, P.R. China
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Wilk MA, McAllister JT, Cooper RF, Dubis AM, Patitucci TN, Summerfelt P, Anderson JL, Stepien KE, Costakos DM, Connor TB, Wirostko WJ, Chiang PW, Dubra A, Curcio CA, Brilliant MH, Summers CG, Carroll J. Relationship between foveal cone specialization and pit morphology in albinism. Invest Ophthalmol Vis Sci 2014; 55:4186-98. [PMID: 24845642 DOI: 10.1167/iovs.13-13217] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism. METHODS We recruited 32 subjects with a clinical diagnosis of albinism. DNA was obtained from 25 subjects, and known albinism genes were analyzed for mutations. Relative inner and outer segment (IS and OS) lengthening (fovea-to-perifovea ratio) was determined from manually segmented spectral domain-optical coherence tomography (SD-OCT) B-scans. Foveal pit morphology was quantified for eight subjects from macular SD-OCT volumes. Ten subjects underwent imaging with adaptive optics scanning light ophthalmoscopy (AOSLO), and cone density was measured. RESULTS We found mutations in 22 of 25 subjects, including five novel mutations. All subjects lacked complete excavation of inner retinal layers at the fovea, though four subjects had foveal pits with normal diameter and/or volume. Peak cone density and OS lengthening were variable and overlapped with that observed in normal controls. A fifth hyper-reflective band was observed in the outer retina on SD-OCT in the majority of the subjects with albinism. CONCLUSIONS Foveal cone specialization and pit morphology vary greatly in albinism. Normal cone packing was observed in the absence of a foveal pit, suggesting a pit is not required for packing to occur. The degree to which retinal anatomy correlates with genotype or visual function remains unclear, and future examination of larger patient groups will provide important insight on this issue.
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Affiliation(s)
- Melissa A Wilk
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - John T McAllister
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Robert F Cooper
- Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States
| | - Adam M Dubis
- Moorfields Eye Hospital, London, United Kingdom Institute of Ophthalmology, University College London, United Kingdom
| | - Teresa N Patitucci
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Phyllis Summerfelt
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | | | - Kimberly E Stepien
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Deborah M Costakos
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Thomas B Connor
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - William J Wirostko
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Pei-Wen Chiang
- Casey Eye Institute Molecular Diagnostics Laboratory, Portland, Oregon, United States
| | - Alfredo Dubra
- Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Christine A Curcio
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham, Alabama, United States
| | - Murray H Brilliant
- Center for Human Genetics, Marshfield Clinic, Marshfield, Wisconsin, United States
| | - C Gail Summers
- Departments of Ophthalmology and Visual Neurosciences and Pediatrics, University of Minnesota, Minneapolis, Minnesota, United States
| | - Joseph Carroll
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, Wisconsin, United States Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin, United States Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
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Functional characterization of two novel splicing mutations in the OCA2 gene associated with oculocutaneous albinism type II. Gene 2013; 537:79-84. [PMID: 24361966 DOI: 10.1016/j.gene.2013.11.102] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 11/10/2013] [Accepted: 11/27/2013] [Indexed: 02/07/2023]
Abstract
Oculocutaneous albinism (OCA) is characterized by hypopigmentation of the skin, hair and eye, and by ophthalmologic abnormalities caused by a deficiency in melanin biosynthesis. OCA type II (OCA2) is one of the four commonly-recognized forms of albinism, and is determined by mutation in the OCA2 gene. In the present study, we investigated the molecular basis of OCA2 in two siblings and one unrelated patient. The mutational screening of the OCA2 gene identified two hitherto-unknown putative splicing mutations. The first one (c.1503+5G>A), identified in an Italian proband and her affected sibling, lies in the consensus sequence of the donor splice site of OCA2 intron 14 (IVS14+5G>A), in compound heterozygosity with a frameshift mutation, c.1450_1451insCTGCCCTGACA, which is predicted to determine the premature termination of the polypeptide chain (p.I484Tfs*19). In-silico prediction of the effect of the IVS14+5G>A mutation on splicing showed a score reduction for the mutant splice site and indicated the possible activation of a newly-created deep-intronic acceptor splice site. The second mutation is a synonymous transition (c.2139G>A, p.K713K) involving the last nucleotide of exon 20. This mutation was found in a young African albino patient in compound heterozygosity with a previously-reported OCA2 missense mutation (p.T404M). In-silico analysis predicted that the mutant c.2139G>A allele would result in the abolition of the splice donor site. The effects on splicing of these two novel mutations were investigated using an in-vitro hybrid-minigene approach that led to the demonstration of the causal role of the two mutations and to the identification of aberrant transcript variants.
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A constitutively active Gαi3 protein corrects the abnormal retinal pigment epithelium phenotype of Oa1-/- mice. PLoS One 2013; 8:e76240. [PMID: 24098784 PMCID: PMC3787026 DOI: 10.1371/journal.pone.0076240] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 08/23/2013] [Indexed: 11/19/2022] Open
Abstract
PURPOSE Ocular Albinism type 1 (OA1) is a disease caused by mutations in the OA1 gene and characterized by the presence of macromelanosomes in the retinal pigment epithelium (RPE) as well as abnormal crossing of the optic axons at the optic chiasm. We showed in our previous studies in mice that Oa1 activates specifically Gαi3 in its signaling pathway and thus, hypothesized that a constitutively active Gαi3 in the RPE of Oa1-/- mice might keep on the Oa1 signaling cascade and prevent the formation of macromelanosomes. To test this hypothesis, we have generated transgenic mice that carry the constitutively active Gαi3 (Q204L) protein in the RPE of Oa1-/- mice and are now reporting the effects that the transgene produced on the Oa1-/- RPE phenotype. METHODS Transgenic mice carrying RPE-specific expression of the constitutively active Gαi3 (Q204L) were generated by injecting fertilized eggs of Oa1-/- females with a lentivirus containing the Gαi3 (Q204L) cDNA. PCR, Southern blots, Western blots and confocal microscopy were used to confirm the presence of the transgene in the RPE of positive transgenic mice. Morphometrical analyses were performed using electron microscopy to compare the size and number of melanosomes per RPE area in putative Oa1-/-, Gαi3 (Q204L) transgenic mice with those of wild-type NCrl and Oa1-/- mice. RESULTS We found a correlation between the presence of the constitutively active Gαi3 (Q204L) transgene and the rescue of the normal phenotype of RPE melanosomes in Oa1-/-, Gαi3 (Q204L) mice. These mice have higher density of melanosomes per RPE area and a larger number of small melanosomes than Oa1-/- mice, and their RPE phenotype is similar to that of wild-type mice. CONCLUSIONS Our results show that a constitutively active Gαi3 protein can by-pass the lack of Oa1 protein in Oa1-/- mice and consequently rescue the RPE melanosomal phenotype.
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Yan N, Liao X, Cai SP, Lan C, Wang Y, Zhou X, Yin Y, Yu W, Liu X. A novel nonsense mutation of the GPR143 gene identified in a Chinese pedigree with ocular albinism. PLoS One 2012; 7:e43177. [PMID: 22916221 PMCID: PMC3423421 DOI: 10.1371/journal.pone.0043177] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 07/18/2012] [Indexed: 02/05/2023] Open
Abstract
Background The purpose of this study was to elucidate the molecular basis of ocular albinism type I in a Chinese pedigree. Methodology/Principal Findings Complete ophthalmologic examinations were performed on 4 patients, 7 carriers and 17 unaffected individuals in this five-generation family. All coding exons of four-point-one (4.1), ezrin, radixin, moesin (FERM) domain-containing 7 (FRMD7) and G protein-coupled receptor 143 (GPR143) genes were amplified by polymerase chain reaction (PCR), sequenced and compared with a reference database. Ocular albinism and nystagmus were found in all patients of this family. Macular hypoplasia was present in the patients including the proband. A novel nonsense hemizygous mutation c.807T>A in the GPR143 gene was identified in four patients and the heterozygous mutation was found in seven asymptomatic individuals. This mutation is a substitution of tyrosine for adenine which leads to a premature stop codon at position 269 (p.Y269X) of GPR143. Conclusions/Significance This is the first report that p.Y269X mutation of GPR143 gene is responsible for the pathogenesis of familial ocular albinism. These results expand the mutation spectrum of GPR143, and demonstrate the clinical characteristics of ocular albinism type I in Chinese population.
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Affiliation(s)
- Naihong Yan
- State Key Laboratory of Biotherapy, Ophthalmic Laboratories, Department of Ophthalmology, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, People’s Republic of China
| | - Xuan Liao
- State Key Laboratory of Biotherapy, Ophthalmic Laboratories, Department of Ophthalmology, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, People’s Republic of China
- Department of Ophthalmology, North Sichuan Medical College, Nanchong, People’s Republic of China
| | - Su-ping Cai
- Shenzhen Eye Hospital, Jinan University, Shenzhen, People’s Republic of China
| | - Changjun Lan
- Department of Ophthalmology, North Sichuan Medical College, Nanchong, People’s Republic of China
| | - Yun Wang
- State Key Laboratory of Biotherapy, Ophthalmic Laboratories, Department of Ophthalmology, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, People’s Republic of China
| | - Xiaomin Zhou
- State Key Laboratory of Biotherapy, Ophthalmic Laboratories, Department of Ophthalmology, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, People’s Republic of China
| | - Yan Yin
- State Key Laboratory of Biotherapy, Ophthalmic Laboratories, Department of Ophthalmology, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, People’s Republic of China
| | - Wenhan Yu
- State Key Laboratory of Biotherapy, Ophthalmic Laboratories, Department of Ophthalmology, Translational Neuroscience Center, West China Hospital, Sichuan University, Chengdu, People’s Republic of China
| | - Xuyang Liu
- Shenzhen Eye Hospital, Jinan University, Shenzhen, People’s Republic of China
- * E-mail:
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Trebušak Podkrajšek K, Stirn Kranjc B, Hovnik T, Kovač J, Battelino T. GPR143 gene mutation analysis in pediatric patients with albinism. Ophthalmic Genet 2012; 33:167-70. [PMID: 22486324 DOI: 10.3109/13816810.2011.559651] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND X-linked ocular albinism type 1 is difficult to differentiate clinically from other forms of albinism in young patients. X-linked ocular albinism type 1 is caused by mutations in the GPR143 gene, encoding melanosome specific G-protein coupled receptor. Patients typically present with moderately to severely reduced visual acuity, nystagmus, strabismus, photophobia, iris translucency, hypopigmentation of the retina, foveal hypoplasia and misrouting of optic nerve fibers at the chiasm. MATERIALS AND METHODS Following clinical ophthalmological evaluation, GPR143 gene mutational analyses were performed in a cohort of 15 pediatric male patients with clinical signs of albinism. RESULTS Three different mutations in the GPR143 gene were identified in four patients, including a novel c.886G>A (p.Gly296Arg) mutation occurring "de novo" and a novel intronic c.360 + 5G>A mutation, identified in two related boys. CONCLUSIONS Four patients with X-linked ocular albinism type 1 were identified from a cohort of 15 boys with clinical signs of albinism using mutation detection methods. Genetic analysis offers the possibility of early definitive diagnosis of ocular albinism type 1 in a significant portion of boys with clinical signs of albinism.
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Ghosh A, Sonavane U, Andhirka SK, Aradhyam GK, Joshi R. Structural insights into human GPCR protein OA1: a computational perspective. J Mol Model 2011; 18:2117-33. [DOI: 10.1007/s00894-011-1228-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 08/18/2011] [Indexed: 11/24/2022]
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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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Hofreiter M, Schöneberg T. The genetic and evolutionary basis of colour variation in vertebrates. Cell Mol Life Sci 2010; 67:2591-603. [PMID: 20229234 PMCID: PMC11115542 DOI: 10.1007/s00018-010-0333-7] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Accepted: 02/24/2010] [Indexed: 12/21/2022]
Abstract
Variation in pigmentation is one of the most conspicuous phenotypic traits in vertebrates. Although mammals show less variation in body pigmentation than other vertebrate groups, the genetics of colour determination and variation is best understood for them. More than 150 genes have been identified that influence pigmentation, and in many cases, the cause for variation in pigmentation has been identified down to the underlying nucleotide changes. These studies show that while some genes are often responsible for deviating pigmentation, similar or almost identical phenotypes even in the same species may be due to mutations in different genes. In this review we will first discuss the current knowledge about the genes and their functions underlying the biochemical pathways that determine pigmentation and then give examples where the mutations responsible for colour variation have been determined. Finally, we will discuss potential evolutionary causes for and consequences of differences in pigmentation between individuals.
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Martinez-Garcia M, Riveiro-Alvarez R, Villaverde-Montero C, Cantalapiedra D, Garcia-Sandoval B, Ayuso C, Trujillo-Tiebas MJ. Identification of a novel deletion in the OA1 gene: report of the first Spanish family with X-linked ocular albinism. Clin Exp Ophthalmol 2010; 38:489-95. [DOI: 10.1111/j.1442-9071.2010.02282.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Micale L, Augello B, Fusco C, Turturo MG, Granatiero M, Piemontese MR, Zelante L, Cecconi A, Merla G. GPR143 mutational analysis in two Italian families with X-linked ocular albinism. Genet Test Mol Biomarkers 2009; 13:527-31. [PMID: 19604113 DOI: 10.1089/gtmb.2009.0030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
X-linked ocular albinism type 1 (OA1) is caused by mutations in G protein-coupled receptor 143 (GPR143) gene, which encodes a membrane glycoprotein localized to melanosomes. GPR143 mainly affects pigment production in the eye, resulting in optic changes associated with albinism, including hypopigmentation of the retina, nystagmus, strabismus, foveal hypoplasia, abnormal crossing of the optic fibers, and reduced visual acuity. We report the mutational analysis of the GPR143 gene on two unrelated families with OA1 using direct sequencing and real-time quantitative polymerase chain reaction. We identified the c.564_565delCT, a 2-bp deletion in family 1, and we mapped the breakpoints at nucleotide level of the novel intragenic deletion g.5360_6371del1012, encompassing exon 2, in family 2. Our results confirm that GPR143 is the major locus for OA1 and that exon 2 is a region of high susceptibility to deletions. Finally, we emphasize the quantitative polymerase chain reaction as a valid tool for diagnosis of deletions in the GPR143 gene.
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Affiliation(s)
- Lucia Micale
- Medical Genetics Unit, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy
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Wang Y, Guo X, Wei A, Zhu W, Li W, Lian S. Identification of a novel mutation in a Chinese family with X-linked ocular albinism. Eur J Ophthalmol 2009; 19:124-8. [PMID: 19123159 DOI: 10.1177/112067210901900118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE The purpose of the study was to evaluate the GPR143 gene (G-protein coupled receptor 143) in a Chinese three-generation family with OA1, including four carriers and a proband with clinical features of X-linked ocular albinism. METHODS The proband underwent a detailed ophthalmologic evaluation. Blood samples of family members were obtained and genomic DNA isolated. Mutational analysis by SSCP and direct sequencing of the GPR143 gene was used to screen all nine exons including the intron/exon junctions. The novel mutation c.943G>T (p.G315X) found in the study was confirmed by DHPLC to exclude the possibility of polymorphism. RESULTS Ophthalmic features of the proband were characteristic of X-linked ocular albinism. The authors identified a novel nonsense mutation p.G315X on exon 8 that was not found in 100 non-albinism subjects by DHPLC. This novel mutation in the GPR143 gene is predicted to subject to nonsense mediated decay. CONCLUSIONS The novel mutation p.G315X in the OA1 gene was identified in a Chinese family with ocular albinism, which is predicted to generate a premature stop codon. These findings extend the mutational spectrum of GPR143 gene and will be useful for gene diagnosis and genetic counseling in Chinese OA1 patients.
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Affiliation(s)
- Y Wang
- Department of Dermatology, Xuan Wu Hospital, Capital Medical University, Beijing, China
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Lopez VM, Decatur CL, Stamer WD, Lynch RM, McKay BS. L-DOPA is an endogenous ligand for OA1. PLoS Biol 2008; 6:e236. [PMID: 18828673 PMCID: PMC2553842 DOI: 10.1371/journal.pbio.0060236] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Accepted: 08/18/2008] [Indexed: 11/25/2022] Open
Abstract
Albinism is a genetic defect characterized by a loss of pigmentation. The neurosensory retina, which is not pigmented, exhibits pathologic changes secondary to the loss of pigmentation in the retina pigment epithelium (RPE). How the loss of pigmentation in the RPE causes developmental defects in the adjacent neurosensory retina has not been determined, but offers a unique opportunity to investigate the interactions between these two important tissues. One of the genes that causes albinism encodes for an orphan GPCR (OA1) expressed only in pigmented cells, including the RPE. We investigated the function and signaling of OA1 in RPE and transfected cell lines. Our results indicate that OA1 is a selective L-DOPA receptor, with no measurable second messenger activity from two closely related compounds, tyrosine and dopamine. Radiolabeled ligand binding confirmed that OA1 exhibited a single, saturable binding site for L-DOPA. Dopamine competed with L-DOPA for the single OA1 binding site, suggesting it could function as an OA1 antagonist. OA1 response to L-DOPA was defined by several common measures of G-protein coupled receptor (GPCR) activation, including influx of intracellular calcium and recruitment of β-arrestin. Further, inhibition of tyrosinase, the enzyme that makes L-DOPA, resulted in decreased PEDF secretion by RPE. Further, stimulation of OA1 in RPE with L-DOPA resulted in increased PEDF secretion. Taken together, our results illustrate an autocrine loop between OA1 and tyrosinase linked through L-DOPA, and this loop includes the secretion of at least one very potent retinal neurotrophic factor. OA1 is a selective L-DOPA receptor whose downstream effects govern spatial patterning of the developing retina. Our results suggest that the retinal consequences of albinism caused by changes in melanin synthetic machinery may be treated by L-DOPA supplementation. Albinism is the loss of pigmentation caused by mutations in one of several different genes that alter pigment synthesis by different mechanisms. In the eye, albinism impairs sensory retina development and causes significant vision problems. Regardless of the genetic mutation that causes albinism, the associated vision problems are the same. Interestingly, none of the pigmentation genes are expressed by the sensory retinal cells affected by albinism but by neighboring, retinal pigment epithelial cells (RPE). Furthermore, loss of pigmentation in RPE somehow leads to imprecise retinal development. To investigate this cellular relationship, we studied OA1, which is encoded by a gene in which mutations cause ocular albinism. OA1 is unique among proteins involved with albinism because OA1 is a potential receptor that could participate in signal transduction rather than being a direct member of the pigment synthesis machinery. We show that the ligand for OA1 is L-DOPA, thus removing OA1 from orphan G-protein coupled receptor (GPCR) status. L-DOPA is a by-product of pigment synthesis, indicating that pigment synthesis and OA1 signaling are intertwined. OA1 signaling is highly selective for L-DOPA, and we show that two closely related molecules, dopamine and tyrosine, bind to OA1 but fail to stimulate signaling. We also show that OA1 signaling controls secretion of a potent neuron survival factor. Taken together, our data suggest that all forms of albinism produce the same retinal defects because of a final common pathway through OA1 signaling with downstream effects on RPE neurotrophic factor secretion. Albinism produces retinal defects, and OA1 is an orphan G-protein-coupled receptor that leads to albinism without acting directly on melanin synthesis. Here the ligand is identified and a mechanism is proposed by which the various forms of albinism signal through OA1, resulting in the same retinal phenotype.
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Affiliation(s)
- Vanessa M Lopez
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
| | - Christina L Decatur
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
| | - W. Daniel Stamer
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
- Department of Physiology, The University of Arizona, Tucson, Arizona, United States of America
| | - Ronald M Lynch
- Department of Physiology, The University of Arizona, Tucson, Arizona, United States of America
| | - Brian S McKay
- Department of Ophthalmology and Vision Science, The University of Arizona, Tucson, Arizona, United States of America
- Department of Cell Biology and Anatomy, The University of Arizona, Tucson, Arizona, United States of America
- * To whom correspondence should be addressed. E-mail:
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Young A, Powelson EB, Whitney IE, Raven MA, Nusinowitz S, Jiang M, Birnbaumer L, Reese BE, Farber DB. Involvement of OA1, an intracellular GPCR, and G alpha i3, its binding protein, in melanosomal biogenesis and optic pathway formation. Invest Ophthalmol Vis Sci 2008; 49:3245-52. [PMID: 18378571 DOI: 10.1167/iovs.08-1806] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Ocular albinism type 1 (OA1) is characterized by abnormalities in retinal pigment epithelium (RPE) melanosomes and misrouting of optic axons. The OA1 gene encodes a G-protein-coupled receptor (GPCR) that coimmunoprecipitates with the G alpha i-subunit of heterotrimeric G-proteins from human melanocyte extracts. This study was undertaken to test whether one of the G alpha i proteins, G alpha i3, signals in the same pathway as OA1 to regulate melanosome biogenesis and axonal growth through the optic chiasm. METHODS Adult G alpha i3(-/-) and Oa1(-/-) mice were compared with their respective control mice (129Sv and B6/NCrl) to study the effects of the loss of G alpha i3 or Oa1 function. Light and electron microscopy were used to analyze the morphology of the retina and the size and density of RPE melanosomes, electroretinograms to study retinal function, and retrograde labeling to investigate the size of the uncrossed optic pathway. RESULTS Although G alpha i3(-/-) and Oa1(-/-) photoreceptors were comparable to those of the corresponding control retinas, the density of their RPE melanosomes was significantly lower than in control RPEs. In addition, the RPE cells of G alpha i3(-/-) and Oa1(-/-) mice showed abnormal melanosomes that were far larger than the largest 129Sv and B6/NCrl melanosomes, respectively. Although G alpha i3(-/-) and Oa1(-/-) mice had normal results on electroretinography, retrograde labeling showed a significant reduction from control in the size of their ipsilateral retinofugal projections. CONCLUSIONS These results indicate that G alpha i3, like Oa1, plays an important role in melanosome biogenesis. Furthermore, they suggest a common Oa1-G alpha i3 signaling pathway that ultimately affects axonal growth through the optic chiasm.
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Affiliation(s)
- Alejandra Young
- Jules Stein Eye Institute, University of California, Los Angeles School of Medicine, Los Angeles, California 90095, USA
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Roma C, Ferrante P, Guardiola O, Ballabio A, Zollo M. New mutations identified in the ocular albinism type 1 gene. Gene 2007; 402:20-7. [PMID: 17822861 DOI: 10.1016/j.gene.2007.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2007] [Revised: 07/05/2007] [Accepted: 07/10/2007] [Indexed: 10/23/2022]
Abstract
As the most common form of ocular albinism, ocular albinism type I (OA1) is an X-linked disorder that has an estimated prevalence of about 1:50,000. We searched for mutations through the human genome sequence draft by direct sequencing on eighteen patients with OA1, both within the coding region and in a thousand base pairs upstream of its start site. Here, we have identified eight new mutations located in the coding region of the gene. Two independent mutations, both located in the most carboxyterminal protein regions, were further characterized by immunofluorescence confocal microscopy, thus showing an impairment in their subcellular distribution into the lysosomal compartment of Cos-7A cells. The mutations found can result in protein misfolding, thus underlining the importance of the structure-function relationships of the protein as a major pathogenic mechanism in ocular albinism. Seven individuals out of eighteen (38.9%) with a clinical diagnosis of ocular albinism showed mutations, thus underlining the discrepancies between the clinical phenotype features and their genotype correlations. We postulate that mutations that have not yet been identified are potentially located in non-coding conserved regions or regulatory sequences of the OA1 gene.
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Fairbank PD, Lee C, Ellis A, Hildebrand JD, Gross JM, Wallingford JB. Shroom2 (APXL) regulates melanosome biogenesis and localization in the retinal pigment epithelium. Development 2006; 133:4109-18. [PMID: 16987870 DOI: 10.1242/dev.02563] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Shroom family proteins have been implicated in the control of the actin cytoskeleton, but so far only a single family member has been studied in the context of developing embryos. Here, we show that the Shroom-family protein,Shroom2 (previously known as APXL) is both necessary and sufficient to govern the localization of pigment granules at the apical surface of epithelial cells. In Xenopus embryos that lack Shroom2 function, we observed defects in pigmentation of the eye that stem from failure of melanosomes to mature and to associate with the apical cell surface. Ectopic expression of Shroom2 in naïve epithelial cells facilitates apical pigment accumulation, and this activity specifically requires the Rab27a GTPase. Most interestingly, we find that Shroom2, like Shroom3 (previously called Shroom),is sufficient to induce a dramatic apical accumulation of the microtubule-nucleating protein γ-tubulin at the apical surfaces of naïve epithelial cells. Together, our data identify Shroom2 as a central regulator of RPE pigmentation, and suggest that, despite their diverse biological roles, Shroom family proteins share a common activity. Finally,because the locus encoding human SHROOM2 lies within the critical region for two distinct forms of ocular albinism, it is possible that SHROOM2mutations may be a contributing factor in these human visual system disorders.
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Affiliation(s)
- Pamela D Fairbank
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA
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Sallmann GB, Bray PJ, Rogers S, Quince A, Cotton RGH, Carden SM. Scanning the ocular albinism 1 (OA1) gene for polymorphisms in congenital nystagmus by DHPLC. Ophthalmic Genet 2006; 27:43-9. [PMID: 16754205 DOI: 10.1080/13816810600677834] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
BACKGROUND Nystagmus is common to all types of albinism. Some subjects with nystagmus lack convincing signs of albinism, have no other visual pathway disease, and are classified as possessing congenital idiopathic nystagmus (CN). It has been postulated that CN may be a form of ocular albinism. METHODS The presence of nystagmus, iris transillumination, and visual acuity were recorded in 39 CN and albino patients and their families. Physical characteristics were also noted. DNA from buccal swabs was obtained for use in denaturing high performance liquid chromatography (DHPLC) and chemical cleavage of mismatch (CCM) to scan several hotspots for X-linked ocular albinism (OA1) mutations. RESULTS Two previously reported polymorphisms were confirmed: neither was found to be a causative mutation. CONCLUSION No correlation was identified between nystagmus and OA1.
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Affiliation(s)
- Georgina B Sallmann
- Genomic Disorders Research Centre, St. Vincent's Hospital, Victoria, Australia
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Vetrini F, Tammaro R, Bondanza S, Surace EM, Auricchio A, De Luca M, Ballabio A, Marigo V. Aberrant splicing in the ocular albinism type 1 gene (OA1/GPR143) is corrected in vitro by morpholino antisense oligonucleotides. Hum Mutat 2006; 27:420-6. [PMID: 16550551 DOI: 10.1002/humu.20303] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
An intronic point mutation was identified in the ocular albinism type 1 (OA1) gene (HUGO symbol, GPR143) in a family with the X-linked form of ocular albinism. Interestingly, the mutation creates a new acceptor splice site in intron 7 of the OA1 gene. In addition to low levels of normally spliced mRNA product of the OA1 gene, the patient samples contained also an aberrantly spliced mRNA with a 165 bp fragment of intron 7 (from position +750 to +914) inserted between exons 7 and 8. The abnormal transcript contained a premature stop codon and was unstable, as revealed by Northern blot analysis. We defined that mutation NC_000023.8:g.25288G>A generated a consensus binding motif for the splicing factor enhancer ASF/SF2, which most likely favored transcription of the aberrant mRNA. Furthermore, it activated a cryptic donor-splice site causing the inclusion between exons 7 and 8 of the 165 bp intronic fragment. Thus, the aberrant splicing is most likely explained by the generation of a de novo splicing enhancer motif. Finally, to rescue OA1 expression in the patient's melanocytes, we designed an antisense morpholino modified oligonucleotide complementary to the mutant sequence. The morpholino oligonucleotide (MO) was able to rescue OA1 expression and restore the OA1 protein level in the patient's melanocytes through skipping of the aberrant inclusion. The use of MO demonstrated that the lack of OA1 was caused by the generation of a new splice site. Furthermore, this technique will lead to new approaches to correct splice site mutations that cause human diseases.
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Dietz ML, Bernaciak TM, Vendetti F, Kielec JM, Hildebrand JD. Differential actin-dependent localization modulates the evolutionarily conserved activity of Shroom family proteins. J Biol Chem 2006; 281:20542-54. [PMID: 16684770 DOI: 10.1074/jbc.m512463200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Shroom is an actin-associated determinant of cell morphology that is required for neural tube closure in both mice and frogs. Shroom regulates this process by causing apical constriction of epithelial cells via a pathway involving myosin II. Here we report on characterization of the Shroom-related proteins Apxl and KIAA1202 and their role in cell architecture. Shroom, Apxl, and KIAA1202 exhibit differing abilities to interact with the actin cytoskeleton. In fibroblasts, Shroom readily associates with actin stress fibers and induces bundling, Apxl is found on cortical actin, and KIAA1202 is localized to a cytoplasmic population of F-actin. In epithelial cells, Apxl and KIAA1202 do not induce apical constriction as Shroom does, but have the capacity to do so if targeted to the apical junctional complex. To determine whether the activity of Shroom-like proteins is conserved in invertebrates, we have tested the ability of the lone Shroomrelated protein in Drosophila, CG8603, to activate the constriction pathway. A chimeric protein consisting of the Shroom targeting domain and the Drosophila protein elicits constriction. Finally, we show that Apxl is involved in regulating the cytoskeletal organization and architecture of endothelial cells. We predict that the ability of Shroom-like proteins to regulate cellular morphology is conserved in evolution and is regulated in part by subcellular localization.
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Affiliation(s)
- Megan L Dietz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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Mayeur H, Roche O, Vêtu C, Jaliffa C, Marchant D, Dollfus H, Bonneau D, Munier FL, Schorderet DF, Levin AV, Héon E, Sutherland J, Lacombe D, Said E, Mezer E, Kaplan J, Dufier JL, Marsac C, Menasche M, Abitbol M. Eight previously unidentified mutations found in the OA1 ocular albinism gene. BMC MEDICAL GENETICS 2006; 7:41. [PMID: 16646960 PMCID: PMC1468396 DOI: 10.1186/1471-2350-7-41] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Accepted: 04/28/2006] [Indexed: 11/24/2022]
Abstract
Background Ocular albinism type 1 (OA1) is an X-linked ocular disorder characterized by a severe reduction in visual acuity, nystagmus, hypopigmentation of the retinal pigmented epithelium, foveal hypoplasia, macromelanosomes in pigmented skin and eye cells, and misrouting of the optical tracts. This disease is primarily caused by mutations in the OA1 gene. Methods The ophthalmologic phenotype of the patients and their family members was characterized. We screened for mutations in the OA1 gene by direct sequencing of the nine PCR-amplified exons, and for genomic deletions by PCR-amplification of large DNA fragments. Results We sequenced the nine exons of the OA1 gene in 72 individuals and found ten different mutations in seven unrelated families and three sporadic cases. The ten mutations include an amino acid substitution and a premature stop codon previously reported by our team, and eight previously unidentified mutations: three amino acid substitutions, a duplication, a deletion, an insertion and two splice-site mutations. The use of a novel Taq polymerase enabled us to amplify large genomic fragments covering the OA1 gene. and to detect very likely six distinct large deletions. Furthermore, we were able to confirm that there was no deletion in twenty one patients where no mutation had been found. Conclusion The identified mutations affect highly conserved amino acids, cause frameshifts or alternative splicing, thus affecting folding of the OA1 G protein coupled receptor, interactions of OA1 with its G protein and/or binding with its ligand.
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Affiliation(s)
- Hélène Mayeur
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
| | - Olivier Roche
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
- Service d'ophtalmologie, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, 75015 Paris, France
| | - Christelle Vêtu
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
| | - Carolina Jaliffa
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
| | - Dominique Marchant
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
| | - Hélène Dollfus
- Laboratoire de diagnostic génétique, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | | | | | | | - Alex V Levin
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8, Canada
| | - Elise Héon
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8, Canada
| | - Joanne Sutherland
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, M5G 1X8, Canada
| | - Didier Lacombe
- Service de Génétique Médicale, Hôpital Pellegrin-Enfants, Bordeaux, France
| | - Edith Said
- Department of Pediatrics and Medical Genetics, St. Luke's Hospital, Gwardamangia, Malta
| | - Eedy Mezer
- Alberto Moscona Department of Ophthalmology, Rambam Health Care Campus, Haifa, Israel
| | - Josseline Kaplan
- Service de Génétique Médicale du CHU Necker-Enfants Malades, Unité INSERM 393, 149 rue de Sèvres, 75015, Paris, France
| | - Jean-Louis Dufier
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
- Service d'ophtalmologie, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, 75015 Paris, France
| | - Cécile Marsac
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
| | - Maurice Menasche
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
| | - Marc Abitbol
- EA no 2502 du ministère de la Recherche, de l'Enseignement Supérieur et la Technologie, CEntre de Recherches Thérapeutiques en Ophtalmologie, (CERTO), Université René Descartes-Paris V, Faculté de Médecine René Descartes-Site Necker, 156 rue de Vaugirard, 75015 Paris cedex, France
- Service d'ophtalmologie, Hôpital Necker-Enfants Malades, 149 rue de Sèvres, 75015 Paris, France
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Schiaffino MV, Tacchetti C. The ocular albinism type 1 (OA1) protein and the evidence for an intracellular signal transduction system involved in melanosome biogenesis. ACTA ACUST UNITED AC 2006; 18:227-33. [PMID: 16029416 DOI: 10.1111/j.1600-0749.2005.00240.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ocular albinism type 1 is an X-linked disorder characterized by severe reduction of visual acuity, retinal hypopigmentation, foveal hypoplasia, optic misrouting and the presence of giant melanosomes (macromelanosomes) in skin melanocytes and retinal pigment epithelium. The protein product of the OA1 gene is a pigment cell specific membrane glycoprotein, displaying structural and functional features of G protein-coupled receptors (GPCRs). However, in contrast to all other previously characterized GPCRs, OA1 is not localized to the plasma membrane, but is targeted to intracellular organelles, namely late endosomes/lysosomes and melanosomes. These unique characteristics suggest that OA1 represents the first example described so far of an exclusively intracellular GPCR and regulates melanosome biogenesis by transducing signals from the organelle lumen to the cytosol. These findings support previous hypotheses that GPCR-mediated signaling might also operate at the internal membranes in mammalian cells.
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Dobson-Stone C, Velayos-Baeza A, Jansen A, Andermann F, Dubeau F, Robert F, Summers A, Lang AE, Chouinard S, Danek A, Andermann E, Monaco AP. Identification of a VPS13A founder mutation in French Canadian families with chorea-acanthocytosis. Neurogenetics 2005; 6:151-8. [PMID: 15918062 DOI: 10.1007/s10048-005-0220-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Accepted: 04/27/2005] [Indexed: 02/03/2023]
Abstract
Mutations in VPS13A cause chorea-acanthocytosis (ChAc), an autosomal recessive neurodegenerative disorder. VPS13A is located in a tail-to-tail arrangement with GNA14 on chromosome 9q21. ChAc shows substantial allelic heterogeneity, with no single VPS13A mutation causing the majority of cases. We examined 11 patients in four French Canadian ChAc pedigrees for mutations in VPS13A. Affected members of three families were homozygous for a 37-kb deletion of the four terminal exons of VPS13A (EX70_EX73del). This deletion also encompasses the two terminal exons of GNA14. Two affected females in family 4 were homozygous for the splicing mutation 4242+1G>T. Remarkably, the affected males in this highly consanguineous pedigree were compound heterozygotes for EX70_EX73del and 4242+1G>T. PCR analysis of the deletion breakpoint junction revealed that an additional patient with French Canadian ancestry was heterozygous for the EX70_EX73del allele. The identification of a common 9q21 haplotype associated with EX70_EX73del in at least four apparently unrelated ChAc families implies that ChAc shows a founder effect in French Canadians, and that routine testing for EX70_EX73del in suspected ChAc cases may therefore be worthwhile in this population. The deletion breakpoint PCR described here will enable rapid identification of both homozygous and heterozygous carriers of EX70_EX73del.
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Affiliation(s)
- Carol Dobson-Stone
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Headington, Oxford, OX3 7BN, UK
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Lauronen L, Jalkanen R, Huttunen J, Carlsson E, Tuupanen S, Lindh S, Forsius H, Sankila EM, Alitalo T. Abnormal crossing of the optic fibres shown by evoked magnetic fields in patients with ocular albinism with a novel mutation in the OA1 gene. Br J Ophthalmol 2005; 89:820-4. [PMID: 15965158 PMCID: PMC1772728 DOI: 10.1136/bjo.2004.060582] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
AIM To perform genealogical and clinical studies in Finnish families with X linked ocular albinism (OA1), including characterisation of the potential misrouting of optic fibres by evaluating visual evoked magnetic fields (VEFs), and to determine the mutation behind the disease. METHODS Three families with OA1 were clinically examined. VEFs were measured in two affected males and in one female carrier to characterise the cortical activation pattern after monocular visual stimulation. The neuronal sources of the VEFs were modelled with equivalent current dipoles (ECDs) in a spherical head model. All coding exons of the OA1 gene were screened for mutations by single strand conformation analysis and direct polymerase chain reaction sequencing. RESULTS Genealogical studies revealed that the three families were all related. The affected males had foveal hypoplasia with reduced visual acuity varying from 20/200 to 20/50, variable nystagmus, iris transillumination, and hypopigmentation of the retinal pigment epithelium. The ECD locations corresponding to the VEFs revealed abnormal crossing of the optic fibres in both affected males, but not in the carrier female. A novel point mutation, leading to a STOP codon, was identified in the fifth exon of the OA1 gene. CONCLUSIONS The data indicate that the novel mutation 640C>T in the OA1 gene is the primary cause of the eye disease in the family studied. VEFs with ECD analysis was successfully used to demonstrate abnormal crossing of the optic fibres.
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Affiliation(s)
- L Lauronen
- Department of Ophthalmology, Helsinki University Central Hospital, Helsinki, Finland
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Boccia A, Petrillo M, di Bernardo D, Guffanti A, Mignone F, Confalonieri S, Luzi L, Pesole G, Paolella G, Ballabio A, Banfi S. DG-CST (Disease Gene Conserved Sequence Tags), a database of human-mouse conserved elements associated to disease genes. Nucleic Acids Res 2005; 33:D505-10. [PMID: 15608249 PMCID: PMC539965 DOI: 10.1093/nar/gki011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The identification and study of evolutionarily conserved genomic sequences that surround disease-related genes is a valuable tool to gain insight into the functional role of these genes and to better elucidate the pathogenetic mechanisms of disease. We created the DG-CST (Disease Gene Conserved Sequence Tags) database for the identification and detailed annotation of human–mouse conserved genomic sequences that are localized within or in the vicinity of human disease-related genes. CSTs are defined as sequences that show at least 70% identity between human and mouse over a length of at least 100 bp. The database contains CST data relative to over 1088 genes responsible for monogenetic human genetic diseases or involved in the susceptibility to multifactorial/polygenic diseases. DG-CST is accessible via the internet at http://dgcst.ceinge.unina.it/ and may be searched using both simple and complex queries. A graphic browser allows direct visualization of the CSTs and related annotations within the context of the relative gene and its transcripts.
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Tsuda H, Birrer MJ, Ito YM, Ohashi Y, Lin M, Lee C, Wong WH, Rao PH, Lau CC, Berkowitz RS, Wong KK, Mok SC. Identification of DNA copy number changes in microdissected serous ovarian cancer tissue using a cDNA microarray platform. ACTA ACUST UNITED AC 2005; 155:97-107. [PMID: 15571795 DOI: 10.1016/j.cancergencyto.2004.03.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2003] [Revised: 02/26/2004] [Accepted: 03/03/2004] [Indexed: 11/30/2022]
Abstract
We have established a method for using a cDNA array platform in combination with degenerate oligonucleotide primer polymerase chain reaction (DOP-PCR) and taramide signal amplification (TSA) to identify DNA copy number abnormalities (CNA) in cancer cell lines and cancer cells procured with laser-based microdissection. To determine the sensitivity and specificity for detecting single-copy gain and loss, receiver-operator curve analysis was performed on hybridization signal ratios generated from non-DOP and DOP amplified female and male DNA using a 10,816-element cDNA microarray. A cutoff value of 1.12 and 1.07 average signal ratio for X-chromosomal genes versus autosomal genes provided a sensitivity and specificity of 50 and 79%, respectively, for non-DOP amplified DNA and a sensitivity and specificity of 50 and 72%, respectively, for DOP amplified DNA. We used this approach to identify DNA copy number abnormalities in the ovarian cancer cell line OVCA633, which has previously been shown to have 12p amplification. Transcription profiling of OVCA633 was also performed. Two amplified and overexpressed genes located on 12p11, KRAS2 and LRMP, were identified; these were validated with quantitative real-time PCR. Subsequently, the same approach was used to identify CNAs and gene expression alterations in 11 microdissected serous ovarian adenocarcinoma cases. Validated data revealed amplification and overexpression of ERBB3 and FOS and deletion and underexpression of KRT6 and APXL in more than 50% of the tissue samples. These results show the feasibility of using the cDNA array platform to identify changes in DNA and mRNA copy number simultaneously in microdissected tumor tissues.
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Affiliation(s)
- Hiroshi Tsuda
- Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Laboratory of Gynecologic Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, BLI-447, 221 Longwood Avenue, Boston, MA 02115, USA
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Faugère V, Tuffery-Giraud S, Hamel C, Claustres M. Identification of three novel OA1 gene mutations identified in three families misdiagnosed with congenital nystagmus and carrier status determination by real-time quantitative PCR assay. BMC Genet 2003; 4:1. [PMID: 12515581 PMCID: PMC140306 DOI: 10.1186/1471-2156-4-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2002] [Accepted: 01/07/2003] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND X-linked ocular albinism type 1 (OA1) is caused by mutations in OA1 gene, which encodes a membrane glycoprotein localised to melanosomes. OA1 mainly affects pigment production in the eye, resulting in optic changes associated with albinism including hypopigmentation of the retina, nystagmus, strabismus, foveal hypoplasia, abnormal crossing of the optic fibers and reduced visual acuity. Affected Caucasian males usually appear to have normal skin and hair pigment. RESULTS We identified three previously undescribed mutations consisting of two intragenic deletions (one encompassing exon 6, the other encompassing exons 7-8), and a point mutation (310delG) in exon 2. We report the development of a new method for diagnosis of heterozygous deletions in OA1 gene based on measurement of gene copy number using real-time quantitative PCR from genomic DNA. CONCLUSION The identification of OA1 mutations in families earlier reported as families with hereditary nystagmus indicate that ocular albinism type 1 is probably underdiagnosed. Our method of real-time quantitative PCR of OA1 exons with DMD exon as external standard performed on the LightCycler trade mark allows quick and accurate carrier-status assessment for at-risk females.
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Affiliation(s)
- Valérie Faugère
- Laboratoire de Génétique Moléculaire, Institut Universitaire de Recherche Clinique IURC et CHU, 641 Avenue du Doyen Gaston Giraud, 34093 Montpellier cedex 5, France
| | - Sylvie Tuffery-Giraud
- Laboratoire de Génétique Moléculaire, Institut Universitaire de Recherche Clinique IURC et CHU, 641 Avenue du Doyen Gaston Giraud, 34093 Montpellier cedex 5, France
| | | | - Mireille Claustres
- Laboratoire de Génétique Moléculaire, Institut Universitaire de Recherche Clinique IURC et CHU, 641 Avenue du Doyen Gaston Giraud, 34093 Montpellier cedex 5, France
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Hegde M, Lewis RA, Richards CS. Diagnostic DNA testing for X-linked ocular albinism (OA1) with a hierarchical mutation screening protocol. GENETIC TESTING 2002; 6:7-14. [PMID: 12180081 DOI: 10.1089/109065702760093852] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Albinism is a group of inherited conditions in which affected individuals have less than normal pigment in the eyes, skin, and hair compared to others of the same race and ethnic background. The prevalence of all types of albinism in the United States is estimated at 1 in 20,000, based on poor epidemiological data. X-linked Nettleship-Falls ocular albinism (XLOA, OA1) affects approximately 1/150,000 males in the population. XLOA effects reduce visual acuity and nystagmus, result in a mild skin and hair phenotype, and occur mostly in XY males. Female carriers of XLOA have normal visual acuity, but often show iris punctate transillumination and a classic pattern of mosaic retinal pigmentation, coarse and grainy in the macula and becoming increasingly reticular into the periphery of the retinal pigment epithelium. Studies of OA1 have shown linkage of a single gene to markers at Xp22.3-p22.2. About 48% of the reported mutations in the OA1 gene are intragenic deletions and about 43% are point mutations. We present a hierarchical strategy for mutation screening for diagnostic testing for OA1 that comprises two tiers: first, multiplex PCR to detect intragenic deletions in the OA1 gene with denaturing high-performance liquid chromatography (dHPLC), and, second, heteroduplex analysis with dHPLC to scan for mutations, with subsequent sequencing of variants to confirm putative mutations in the OA1 gene. Prenatal diagnosis can be provided for families when the mutation has been firmly identified. We have validated this procedure with positive controls that were identified in patients by Southern blot, single-stranded conformation polymorphism (SSCP), and sequencing. In this hierarchical strategy, these procedures have an analytical sensitivity of > 99%.
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Affiliation(s)
- M Hegde
- Diagnostic Sequencing Laboratory, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
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Schiaffino MV, Dellambra E, Cortese K, Baschirotto C, Bondanza S, Clementi M, Nucci P, Ballabio A, Tacchetti C, De Luca M. Effective retrovirus-mediated gene transfer in normal and mutant human melanocytes. Hum Gene Ther 2002; 13:947-57. [PMID: 12031127 DOI: 10.1089/10430340252939050] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Melanocytes represent the second most important cell type in the skin and are primarily responsible for the pigmentation of skin, hair, and eyes. Their function may be affected in a number of inherited and acquired disorders, characterized by hyperpigmentation or hypopigmentation, consequent aesthetic problems, and increased susceptibility to sun-mediated skin damage and photocarcinogenesis. Nevertheless, the possibility of genetically manipulating human melanocytes has been hampered so far by a number of limitations, including their resistance to retroviral infection. To address the problem of human melanocyte transduction, we generated a melanocyte culture from a patient affected with ocular albinism type 1 (OA1), an X-linked pigmentation disorder, characterized by severe reduction of visual acuity, retinal hypopigmentation, and the presence of macromelanosomes in skin melanocytes and retinal pigment epithelium (RPE). The cultured patient melanocytes displayed a significant impairment in replication ability and showed complete absence of endogenous OA1 protein, thus representing a suitable model for setting up an efficient gene transfer procedure. To correct the genetic defect in these cells, we used a retroviral vector carrying the OA1 cDNA and exploited a melanocyte-keratinocyte coculturing approach. Despite their lower replication rate with respect to wildtype cells, the patient melanocytes were efficiently transduced and readily selected in vitro, and were found to express, process, and properly sort large amounts of recombinant OA1 protein. These results indicate the feasibility of efficiently and stably transducing in vitro not only normal neonatal, but also mutant adult, human melanocytes with nonmitogenic genes.
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Oetting WS. New insights into ocular albinism type 1 (OA1): Mutations and polymorphisms of the OA1 gene. Hum Mutat 2002; 19:85-92. [PMID: 11793467 DOI: 10.1002/humu.10034] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Albinism ocular type 1 (OA1) is an X-linked type of albinism that mainly effects pigment production in the eye, resulting in hypopigmentation of the retina, nystagmus, strabismus, foveal hypoplasia, abnormal crossing of the optic fibers, and reduced visual acuity. The OA1 gene is located on chromosome Xp22.32 and the coding sequence is divided into nine exons. The protein is an integral transmembrane protein that has weak similarities to G protein-coupled receptors. A total of 25 missense, two nonsense, nine frameshift, and five splicing mutations have been reported in the OA1 gene associated with OA1. There are also several deletions of some or all exons of the OA1 gene with deletions of exon 2 resulting from unequal crossing-over, due to flanking Alu repeats. Mutation and polymorphism data on this gene is available from the International Albinism Center - Albinism Database web site (http://www.cbc.umn.edu/tad).
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Affiliation(s)
- William S Oetting
- Department of Medicine and Institute of Human Genetics, University of Minnesota, Minneapolis, Minnesota, USA
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Preising M, Op de Laak JP, Lorenz B. Deletion in the OA1 gene in a family with congenital X linked nystagmus. Br J Ophthalmol 2001; 85:1098-103. [PMID: 11520764 PMCID: PMC1724103 DOI: 10.1136/bjo.85.9.1098] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIMS To elucidate the molecular genetic defect of X linked congenital nystagmus associated with macular hypoplasia in three white males of a three generation family with clear features of ocular albinism in only one of them. METHODS A three generation family with congenital nystagmus following X linked inheritance, and associated with macular hypoplasia was clinically examined (three males and two obligate carriers). Flash VEP was performed to look for albino misrouting. DNA samples were subjected to PCR and subsequent analysis using SSCP for all exons of the OA1 gene. RT-PCR was performed on a mRNA preparation from a naevus from one patient. PCR products presenting divergent banding patterns in SSCP and from the RT-PCR were sequenced directly using cycle sequencing with fluorescent chain termination nucleotides and electrophoresis in a capillary sequencer. RESULTS The index case (patient 1, IV.1) was diagnosed with X linked OA1 at the age of 3 months because of typical clinical features: congenital nystagmus, iris translucency, macular hypoplasia, fundus hypopigmentation, normal pigmentation of skin and hair, and typical carrier signs of OA1 in his mother and maternal grandmother. Pigmentation of the iris and fundus had increased at the last examination at age 4 years. Albino misrouting was present at this age. In the maternal uncle (III.3, 51 years) who also suffered from congenital nystagmus there was clear macular hypoplasia and stromal focal hypopigmentation of the iris but no iris translucency or fundus hypopigmentation. Patient 3 (II.3, 79 years, maternal uncle of patient III.3) had congenital nystagmus and was highly myopic. The fundus appearance was typical for excessive myopia including macular changes. The iris did not show any translucency. Molecular genetic analysis revealed a novel 14 bp deletion of the OA1 gene at nt816 in exon 6. The mutation abolishes four amino acids (Leu 253-Ile-Ile-Cys) and covers the splice site. Nucleotides 814/815 are used as a new splice donor thus producing a frame shift in codon 252 and a new stop codon at codon 259. CONCLUSIONS Macular hypoplasia without clinically detectable hypopigmentation as the only sign of X linked OA1 has been reported occasionally in African-American, Japanese, and white patients. The present family shows absent hypopigmentation in two patients of a white family with a deletion in the OA1 gene. We propose a model of OA1 that allows increase of pigmentation with age. We hypothesise that macular hypoplasia in all forms of albinism depends on the extracellular DOPA level during embryogenesis, and that in OA1 postnatal normalisation of the extracellular DOPA level due to delayed distribution and membrane budding/fusion of melanosomes in melanocytes results in increasing pigmentation.
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Affiliation(s)
- M Preising
- Department of Paediatric Ophthalmology, Strabismology, and Ophthalmogenetics, University of Regensburg, 93042 Regensburg, Germany.
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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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Shen B, Rosenberg B, Orlow SJ. Intracellular distribution and late endosomal effects of the ocular albinism type 1 gene product: consequences of disease-causing mutations and implications for melanosome biogenesis. Traffic 2001; 2:202-11. [PMID: 11260525 DOI: 10.1034/j.1600-0854.2001.020306.x] [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: 11/23/2022]
Abstract
To investigate the function of ocular albinism type 1 (OA1), the gene responsible for X-linked ocular albinism, we employed a construct containing murine Oa1 fused to green fluorescent protein (GFP) in a heterologous COS cell expression system. The cellular distribution of wild-type (WT) Oa1 protein and Oa1 proteins reflecting mutations causing X-linked ocular albinism were examined. Comparison with different organelle markers revealed that Oa1-GFP localized to the late endolysosomal compartments. Some Oa1 mutant proteins failed to exit the endoplasmic reticulum (ER) (Class I mutants), while other mutants partially (Class II mutants) or fully (Class III mutants) exited the ER and trafficked to endolysosomal compartments. We observed that expression of WT Oa1-GFP in COS cells caused an apparent enlargement of late endosomes and a redistribution of the mannose-6-phosphate receptor (M6PR). None of the mutants displayed the full range of effects on the redistribution of M6PR exhibited by WT Oa1. The effects of Oa1 on late endosome structure and content are thus likely to reflect an important biological property of Oa1. We propose that OA1 is involved in reorganizing the endolysosomal compartment as a necessary step in ocular melanosome biogenesis.
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Affiliation(s)
- B Shen
- The Ronald O. Perelman Department of Dermatology and the Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA
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Sankaranarayanan K, Chakraborty R. Ionizing radiation and genetic risks. XII. The concept of "potential recoverability correction factor" (PRCF) and its use for predicting the risk of radiation-inducible genetic disease in human live births. Mutat Res 2000; 453:129-81. [PMID: 11024484 DOI: 10.1016/s0027-5107(00)00107-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Genetic risks of radiation exposure of humans are generally expressed as expected increases in the frequencies of genetic diseases over those that occur naturally in the population as a result of spontaneous mutations. Since human data on radiation-induced germ cell mutations and genetic diseases remain scanty, the rates derived from the induced frequencies of mutations in mouse genes are used for this purpose. Such an extrapolation from mouse data to the risk of genetic diseases will be valid only if the average rates of inducible mutations in human genes of interest and the average rates of induced mutations in mice are similar. Advances in knowledge of human genetic diseases and in molecular studies of radiation-induced mutations in experimental systems now question the validity of the above extrapolation. In fact, they (i) support the view that only in a limited number of genes in the human genome, induced mutations may be compatible with viability and hence recoverable in live births and (ii) suggest that the average rate of induced mutations in human genes of interest from the disease point of view will be lower than that assumed from mouse results. Since, at present, there is no alternative to the use of mouse data on induced mutation rates, there is a need to bridge the gap between these and the risk of potentially inducible genetic diseases in human live births. In this paper, we advance the concept of what we refer to here as "the potential recoverability correction factor" (PRCF) to bridge the above gap in risk estimation and present a method to estimate PRCF. In developing the concept of PRCF, we first used the available information on radiation-induced mutations recovered in experimental studies to define some criteria for assessing potential recoverability of induced mutations and then applied these to human genes on a gene-by-gene basis. The analysis permitted us to estimate unweighted PRCFs (i.e. the fraction of genes among the total studied that might contribute to recoverable induced mutations) and weighted PRCFs (i.e. PRCFs weighted by the incidences of the respective diseases). The estimates are: 0.15 (weighted) to 0.30 (unweighted) for autosomal dominant and X-linked diseases and 0.02 (weighted) to 0.09 (unweighted) for chronic multifactorial diseases. The PRCF calculations are unnecessary for autosomal recessive diseases since the risks projected for the first few generations even without using PRCFs are already very small. For congenital abnormalities, PRCFs cannot be reliably estimated. With the incorporation of PRCF into the equation used for predicting risk, the risk per unit dose becomes the product of four quantities (risk per unit dose=Px(1/DD)xMCxPRCF) where P is the baseline frequency of the genetic disease, 1/DD is the relative mutation risk per unit dose, MC is the mutation component and PRCF is the disease-class-specific potential recoverability correction factor instead of the first three (as has been the case thus far). Since PRCF is a fraction, it is obvious that the estimate of risk obtained with the revised risk equation will be smaller than previously calculated values.
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Affiliation(s)
- K Sankaranarayanan
- Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, Sylvius Laboratories, Wassenaarseweg 72, 2333, AL Leiden, The Netherlands.
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Samaraweera P, Donatien PD, Qazi S, Kobayashi T, Hearing VJ, Panthier JJ, Orlow SJ. Identification and characterization of a melanocyte-specific novel 65-kDa peripheral membrane protein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 266:924-34. [PMID: 10583387 DOI: 10.1046/j.1432-1327.1999.00930.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In order to study proteins of the melanosome, we developed a panel of antisera against various protein fractions of melanosomes from B16 melanoma cells. An antiserum raised against a Triton X-100 insoluble fraction of melanosomes recognized a 65-kDa protein in melanocytes from mice homozygous for the buff mutation, but not in their wild type counterparts. Further studies were conducted using a specific, second generation antiserum raised against the purified protein. The protein was also detected in melanocytes cultured from albino mice, but absent in cultured mouse cell lines not of melanocyte origin. Density gradient centrifugation of subcellular organelles and indirect immunofluorescent cell staining, indicated that the protein was associated with melanosomes and vesicles. The protein on intact organelles could be made soluble using sodium carbonate, and digested with proteases in the absence of detergent suggesting that it was a peripheral membrane protein localized on the cytosolic face of organelle membranes. Metabolic labelling of cells and N-glycosidase F digestion of cell extracts indicated that the protein was not N-glycosylated. Based on its intracellular localization and biochemical defects in the buff mouse, a potential role has been suggested for the 65-kDa protein in intracellular membrane trafficking.
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Affiliation(s)
- P Samaraweera
- Department of Dermatology, New York University School of Medicine, New York, NY, USA
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