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Ullah MI. Clinical and Mutation Spectrum of Autosomal Recessive Non-Syndromic Oculocutaneous Albinism (nsOCA) in Pakistan: A Review. Genes (Basel) 2022; 13:genes13061072. [PMID: 35741834 PMCID: PMC9222488 DOI: 10.3390/genes13061072] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 06/09/2022] [Accepted: 06/13/2022] [Indexed: 02/01/2023] Open
Abstract
Oculocutaneous albinism (OCA) is an autosomal recessive syndromic and non-syndromic defect with deficient or a complete lack of the melanin pigment. The characteristics of OCA appears in skin, hair, and eyes with variable degree of pigmentation. Clinical manifestations of OCA include nystagmus, photophobia, reduced visual acuity, hypo-plastic macula, and iris trans-illumination. There are eight OCA types (OCA1–8) documented with non-syndromic characteristics. Molecular studies identified seven genes linked to the OCA phenotype (TYR, OCA2, TYRP1, SLC45A2, SLC24A5, C10orf11, and DCT) and one locus (OCA5) in consanguineous and sporadic albinism. The complications of OCA result in skin cancer and variable syndromes such as Hermansky–Pudlak syndrome (HPS) Chediak–Higashi syndrome (CHS). In the Pakistani population, autosomal recessive non-syndromic OCA is common and is associated with a large number of consanguineous families, and mutations in genes of non-syndromic types are reported. This review highlights the updates on the genetic mutation of OCA genes reported from Pakistani families. Several studies reported the genetic mutations in OCA1, OCA2, OCA3, OCA4, and OCA6 albinism in Pakistani families. A locus, OCA5, was also reported from the Pakistani population, but the gene has not been identified. A new type of OCA8 was identified due to the DCT gene mutation, and it is also reviewed here.
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Affiliation(s)
- Muhammad Ikram Ullah
- Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, Jouf University, Sakaka 75471, Aljouf, Saudi Arabia
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2
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Saito T, Okamura K, Kosaki R, Wakamatsu K, Ito S, Nakajima O, Yamashita H, Hozumi Y, Suzuki T. Impact of a SLC24A5 variant on the retinal pigment epithelium of a Japanese patient with oculocutaneous albinism type 6. Pigment Cell Melanoma Res 2021; 35:212-219. [PMID: 34870899 DOI: 10.1111/pcmr.13024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/24/2021] [Accepted: 12/01/2021] [Indexed: 11/27/2022]
Abstract
Oculocutaneous albinism (OCA) 6 is a non-syndromic type of OCA that has distinct ocular symptoms and variable cutaneous hypopigmentation. The causative gene of OCA6 is SLC24A5, which encodes NCKX5, a K+ -dependent Na+ /Ca2+ exchanger 5. NCKX5 is involved in the maturation of melanosomes, but its function is still unclear. In this study, we characterized a Japanese patient with OCA6. Genetic analysis revealed compound heterozygous variants in SLC24A5, c.590 + 1dupG, and c.598G>A (p.G200R). To clarify the functional significance of the missense variant, we generated a knock-in (KI) mouse model carrying the mouse homolog of the G200R variant using the CRISPR/Cas9 system. Chemical analysis showed decreased amounts of eumelanin in the hair and skin of KI mice, while levels of benzothiazine units in pheomelanin were significantly increased in their hair. Retinal pigment was also decreased in KI mice. Notably, a histopathologic study revealed a significant pigment loss in the retinal pigment epithelium (RPE) but not in the choroid. Immunohistochemically, the expression of NCKX5 in the RPE was decreased but was maintained in the choroid of KI mice. These findings could explain the difference in phenotypic severity between eye symptoms and hypopigmentation in the skin/hair.
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Affiliation(s)
- Toru Saito
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Ken Okamura
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Rika Kosaki
- Division of Medical Genetics, Department of Medical Subspecialties, National Center for Child Health and Development, Tokyo, Japan
| | - Kazumasa Wakamatsu
- Institute for Melanin Chemistry, Fujita Health University, Toyoake, Japan
| | - Shosuke Ito
- Institute for Melanin Chemistry, Fujita Health University, Toyoake, Japan
| | - Osamu Nakajima
- Research Center for Molecular Genetics, Institute for Promotion of Medical Science Research, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Hidetoshi Yamashita
- Department of Ophthalmology, Yssamagata University Faculty of Medicine, Yamagata, Japan
| | - Yutaka Hozumi
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Tamio Suzuki
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
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3
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Okamura K, Suzuki T. Current landscape of Oculocutaneous Albinism in Japan. Pigment Cell Melanoma Res 2020; 34:190-203. [PMID: 32969595 DOI: 10.1111/pcmr.12927] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/05/2020] [Accepted: 09/10/2020] [Indexed: 12/16/2022]
Abstract
Oculocutaneous albinism (OCA), which is roughly divided into non-syndromic and syndromic OCA, is a group of autosomal recessive disorders caused by mutations in genes associated with pigmentation. Patients with OCA have hypopigmentation and ocular manifestations such as photophobia, amblyopia, and nystagmus. Hermansky-Pudlak syndrome (HPS), the most common syndromic OCA, is characterized by the additional features of a bleeding tendency and other critical systemic comorbidities such as pulmonary fibrosis and immunodeficiency. NGS-based gene analyses have identified several new causative genes for OCA and have detected rare subtypes of OCA with high accuracy including Japanese patients. In our survey of 190 Japanese OCA patients/families, OCA4 is the most common subtype (25.3%) followed by OCA1 (20.0%), HPS1 (14.7%), and OCA2 (8.4%). Similar to the A481T variant in OCA2, which is associated with a mild form of OCA2 and skin color variation, the c.-492_489delAATG variant located in the promoter region of SLC45A2 has been uniquely identified in Japanese patients with a mild form of OCA4. Further, rare OCA subtypes, including OCA3, HPS2, HPS3, HPS4, HPS5, HPS6, and HPS9, have also been identified in Japanese patients. The clinical characteristics and underlying molecular mechanisms of each subtype of OCA are concisely summarized in this review.
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Affiliation(s)
- Ken Okamura
- Department of Dermatology, Faculty of Medicine, Yamagata University, Yamagata, Japan
| | - Tamio Suzuki
- Department of Dermatology, Faculty of Medicine, Yamagata University, Yamagata, Japan
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Yousaf S, Sethna S, Chaudhary MA, Shaikh RS, Riazuddin S, Ahmed ZM. Molecular characterization of SLC24A5 variants and evaluation of Nitisinone treatment efficacy in a zebrafish model of OCA6. Pigment Cell Melanoma Res 2020; 33:556-565. [PMID: 32274888 DOI: 10.1111/pcmr.12879] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 02/26/2020] [Accepted: 03/30/2020] [Indexed: 02/06/2023]
Abstract
Skin pigmentation is a highly heterogeneous trait with diverse consequences worldwide. SLC24A5, encoding a potent K+ -dependent Na+ /Ca2+ exchanger, is among the known color-coding genes that participate in melanogenesis by maintaining pH in melanosomes. Deficient SLC24A5 activity results in oculocutaneous albinism (OCA) type 6 in humans. In this study, by utilizing a exome sequencing (ES) approach, we identified two new variants [p. (Gly110Arg) and p. (IIe189Ilefs*1)] of SLC24A5 cosegregating with the OCA phenotype, including nystagmus, strabismus, foveal hypoplasia, albinotic fundus, and vision impairment, in three large consanguineous Pakistani families. Both of these variants failed to rescue the pigmentation in zebrafish slc24a5 morphants, confirming the pathogenic effects of the variants. We also phenotypically characterized a commercially available zebrafish mutant line (slc24a5ko ) that harbors a nonsense (p.Tyr208*) allele of slc24a5. Similar to morphants, homozygous slc24a5ko mutants had significantly reduced melanin content and pigmentation. Next, we used these slc24a5ko zebrafish mutants to test the efficacy of nitisinone, a compound known to increase ocular and fur pigmentation in OCA1 (TYR) mutant mice. Treatment of slc24a5ko mutant zebrafish embryos with varying doses of nitisinone did not improve melanin production and pigmentation, suggesting that treatment with nitisinone is unlikely to be therapeutic in OCA6 patients.
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Affiliation(s)
- Sairah Yousaf
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.,Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan
| | - Saumil Sethna
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA
| | | | - Rehan S Shaikh
- Institute of Molecular Biology & Biotechnology, Bahauddin Zakariya University, Multan, Pakistan
| | - Saima Riazuddin
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.,Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Zubair M Ahmed
- Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, Baltimore, MD, USA.,Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD, USA.,Department of Ophthalmology and Visual Sciences, School of Medicine, University of Maryland, Baltimore, MD, USA
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5
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Zhang Y, Zhang Y, Liu T, Bai D, Yang X, Li W, Wei A. Identification of two Chinese oculocutaneous albinism type 6 patients and mutation updates of the
SLC
24A5
gene. J Dermatol 2019; 46:1027-1030. [DOI: 10.1111/1346-8138.15065] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Accepted: 08/01/2019] [Indexed: 11/29/2022]
Affiliation(s)
- Yunlan Zhang
- Department of Dermatology Beijing Tongren Hospital Capital Medical University BeijingChina
| | - Yingzi Zhang
- Department of Dermatology Shunyi Women and Children's Hospital of Beijing Children's Hospital BeijingChina
| | - Teng Liu
- Department of Dermatology Beijing Tongren Hospital Capital Medical University BeijingChina
| | - Dayong Bai
- Department of Ophthalmology Beijing Children's Hospital Capital Medical University BeijingChina
| | - Xiumin Yang
- Department of Dermatology Beijing Tongren Hospital Capital Medical University BeijingChina
| | - Wei Li
- Laboratory for Genetics of Birth Defects Beijing Pediatric Research Institute Beijing Children's Hospital Capital Medical University National Center for Children's Health BeijingChina
- Shunyi Women and Children's Hospital of Beijing Children's Hospital Beijing China
| | - Aihua Wei
- Department of Dermatology Beijing Tongren Hospital Capital Medical University BeijingChina
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Zhong Z, Gu L, Zheng X, Ma N, Wu Z, Duan J, Zhang J, Chen J. Comprehensive analysis of spectral distribution of a large cohort of Chinese patients with non-syndromic oculocutaneous albinism facilitates genetic diagnosis. Pigment Cell Melanoma Res 2019; 32:672-686. [PMID: 31077556 PMCID: PMC6852118 DOI: 10.1111/pcmr.12790] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 03/31/2019] [Accepted: 05/05/2019] [Indexed: 12/25/2022]
Abstract
Non-syndromic oculocutaneous albinism (nsOCA) is a group of genetically heterogeneous autosomal recessive disorders with complete lack or decrease pigmentation in skin, hair, and eyes. TYR, OCA2, TYRP1, SLC45A2, SLC24A5, and LRMDA were reported to cause OCA1-4 and OCA6-7, respectively. By sequencing all the known nsOCA genes in 114 unrelated Chinese nsOCA patients combined with In silico analyses, splicing assay, and classification of variants according to the standards and guidelines of American College of Medical Genetics and Genomics, we detected seventy-one different OCA-causing variants separately in TYR, OCA2, SLC45A2, and SLC24A5, including thirty-one novel variants (13 in TYR, 11 in OCA2, and 7 in SLC45A2). This study shows that OCA1 is the most common (75/114) and OCA2 ranks the second most common (16/114) in Chinese. 99 patients of our cohort were caused by variants of all the known nsOCA genes. Cutaneous phenotypes of OCA1, OCA2, and OCA4 patients were shown in this study. The second OCA6 case in China was identified here. These data expand the spectrum of OCA variants as well phenotype and facilitate clinical implement of Chinese OCA patients.
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Affiliation(s)
- Zilin Zhong
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China.,Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai, China
| | - Li Gu
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China
| | - Xiujie Zheng
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China
| | - Nengjun Ma
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China
| | - Zehua Wu
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China
| | - Juan Duan
- Department of Auxiliary Reproductive, Jiujiang Maternal and Child Health Hospital, Jiujiang, China
| | - Jun Zhang
- Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai, China
| | - Jianjun Chen
- Department of Pediatrics of Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Medical Genetics, Tongji University School of Medicine, Shanghai, China.,Department of Regenerative Medicine, Tongji University School of Medicine, Shanghai, China
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7
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Comprehensive Review of the Genetics of Albinism. JOURNAL OF VISUAL IMPAIRMENT & BLINDNESS 2018. [DOI: 10.1177/0145482x1811200604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Introduction It is important to understand albinism, since it is a disorder associated with visual impairment, predisposition to malignant melanomas, and social stigma. The main objective of this article is to review the genetics and biologic mechanisms of the non-syndromic albinism subtypes and to describe associated clinical manifestations. We also discuss research on its treatments. Methods A review of the published literature on albinism subtypes was performed, spanning basic laboratory research, published case reports, and experiences of people with albinism. Results Clear progress has been made in comprehending the causes of albinism; research has shed light on the complexity of the disorder and has led to the molecular classification of subtypes. Discussion Despite the increase in knowledge with regards to albinism, gaps still exist. It is important to continue the pursuit of unraveling the mechanism of the disorder and to monitor the frequency of the subtypes worldwide in order to aid in the development of treatments. Furthermore, disseminating knowledge of albinism is crucial for future progress. Implications for practitioners Albinism is a disorder characterized by hypopigmentation of the hair, skin, and eyes, with accompanying ocular abnormalities that remain relatively stable throughout life. The disorder is defined by a spectrum of pigmentation where albinism is more evident among individuals of dark complexion than their lighter-pigmented peers. Patients with albinism require protection against sun exposure and special resources to address visual impairments. When albinism patients are diagnosed and properly accommodated, they generally report a positive quality of life.
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Wang Y, Zhou YF, Shen N, Zhu YW, Tan K, Wang X. Identification of a Homozygous Missense Mutation in the TYR Gene in a Chinese Family with OCA1. Curr Med Sci 2018; 38:932-936. [PMID: 30341532 DOI: 10.1007/s11596-018-1965-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 09/20/2018] [Indexed: 12/28/2022]
Abstract
Oculocutaneous albinism (OCA) is an autosomal recessive pigmentation abnormality, characterized by variable hair, skin, and ocular hypopigmentation. OCA1 is the most frequent subtype of OCA, caused by mutations in the tyrosinase gene (TYR). In this study, we investigated the genetic mutation of a Chinese family with a female OCA patient who came for genetic counseling before pregnancy. Complete physical examination was performed, and DNA from blood samples was collected from the family members. Mutations of TYR, OCA2, and SLC45A2 genes were examined in the proband, and verified in her parents by Sanger sequencing. Large deletion or duplication of TYR and OCA2 genes was detected by multiplex ligation-dependent probe amplification (MLPA). A homozygous TYR c.307T>C (p.Cys103Arg) missense mutation was identified in the proband, and both parents were heterozygous carriers. No large deletion or duplication was found in the proband. This mutation was absent in 1000G, ExAC, or HGMD database, and multiple lines of in silico tools supported a deleterious effect. These results suggest that TYR c.307T>C mutation might be responsible for OCA1, and our study further expands the mutation spectrum of OCA1 in the Chinese population.
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Affiliation(s)
- Yan Wang
- Department of Neurosurgery, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yi-Fan Zhou
- Reproductive Medicine Center, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Na Shen
- Department of Laboratory Medicine, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yao-Wu Zhu
- Department of Laboratory Medicine, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Kun Tan
- Department of Infection Control, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
| | - Xiong Wang
- Department of Laboratory Medicine, Huazhong University of Science and Technology, Wuhan, 430030, China.
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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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