DOCSLIB.ORG

Repositioning of Nitisinone to Treat Oculocutaneous Albinism

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Repositioning of Nitisinone to Treat Oculocutaneous Albinism Informed reasoning: repositioning of nitisinone to treat oculocutaneous albinism Prashiela Manga, Seth J. Orlow J Clin Invest. 2011;121(10):3828-3831. https://doi.org/10.1172/JCI59763. Commentary Oculocutaneous albinism (OCA) is a group of genetic disorders characterized by hypopigmentation of the skin, hair, and eyes. Affected individuals experience reduced visual acuity and substantially increased skin cancer risk. There are four major types of OCA (OCA1–OCA4) that result from disruption in production of melanin from tyrosine. Current treatment options for individuals with OCA are limited to attempts to correct visual problems and counseling to promote use of sun protective measures. However, Onojafe et al., reporting in this issue of the JCI, provide hope for a new treatment approach for OCA, as they demonstrate that treating mice that model OCA-1b with nitisinone, which is FDA approved for treating hereditary tyrosinemia type 1, elevates plasma tyrosine levels, and increases eye and hair pigmentation. Find the latest version: https://jci.me/59763/pdf commentaries Informed reasoning: repositioning of nitisinone to treat oculocutaneous albinism Prashiela Manga and Seth J. Orlow Ronald O. Perelman Department of Dermatology and Department of Cell Biology, New York University School of Medicine, New York, New York, USA. Oculocutaneous albinism (OCA) is a group of genetic disorders characterized Melanin synthesis and its disruption by hypopigmentation of the skin, hair, and eyes. Affected individuals experi- in OCA ence reduced visual acuity and substantially increased skin cancer risk. There Tyrosinase, a type I membrane protein, are four major types of OCA (OCA1–OCA4) that result from disruption in catalyzes the first and rate-limiting reac- production of melanin from tyrosine. Current treatment options for individ- tion during melanin synthesis. Unlike many uals with OCA are limited to attempts to correct visual problems and coun- membrane proteins that exit the ER rapidly, seling to promote use of sun protective measures. However, Onojafe et al., tyrosinase is retained for an unusually long reporting in this issue of the JCI, provide hope for a new treatment approach period prior to transport to the Golgi, which for OCA, as they demonstrate that treating mice that model OCA-1b with suggests that it undergoes highly regulated/ nitisinone, which is FDA approved for treating hereditary tyrosinemia type 1, complex early processing. Maturation of elevates plasma tyrosine levels, and increases eye and hair pigmentation. tyrosinase begins during translation, when the peptide is inserted into the ER mem- Oculocutaneous albinism dence of OCA4 is not known; however, it brane by Sec61, then bound by the folding Melanin is a biopolymer synthesized from appears to be more prevalent in Japanese chaperone BiP (also known as HSPA5) (Fig- tyrosine. Upon synthesis, it is deposited in populations (7). ure 1). Additional chaperones — calnexin, specialized organelles (melanosomes) in OCAs are characterized by decreased or then calreticulin — subsequently bind the neural crest–derived melanocytes found absent melanin in skin, hair, and eyes. In peptide to facilitate glycosylation. The fol- in the skin, hair follicles, iris, uveal tract, skin, melanin plays a central role in pro- dase ER protein 57 (ERp57) is also recruited and inner ear as well as in retinal pig- tection from UV-induced carcinogenesis. to the complex to catalyze disulfide bond mented epithelium (RPE) derived from Thus, individuals with OCA are highly formation after signal sequence cleavage. the optic cup. Oculocutaneous albinism susceptible to skin cancers, particularly The processed peptide is then subject to the (OCA) denotes a group of common auto- squamous cell carcinoma. During embryo- ER quality control system that ensures that somal-recessive disorders that result from genesis, melanin synthesis in the RPE only correctly folded proteins exit the ER. disruption of melanin synthesis. There are affects development of the fovea and of Correctly folded tyrosinase is transported to four major forms: OCA1, which is caused adjacent retinal ganglion cells, which in the Golgi, where it undergoes additional gly- by mutations in the tyrosinase gene (TYR) turn regulate decussation of the nerve con- cosylation. Misfolded tyrosinase is retained (1); OCA2, caused by mutations in OCA2 necting the retina to brain at the optic chi- in the ER, undergoing cycles of folding and (2); OCA3, caused by mutations in the asm. Numerous structural abnormalities unfolding, until it is eventually targeted for tyrosinase-related protein 1 gene (TYRP1) ensue if melanogenesis is deficient. In the proteasomal degradation (10). (3); and OCA4, caused by mutations in the adult eye, melanin appears important for Many OCA1-causing TYR mutations solute carrier family 45, member 2 gene reducing light scatter and aiding acuity. result in a protein that fails to fold and (SLC45A2) (4). OCA1 affects approximate- Individuals with OCA consequently suffer is therefore unable to exit the ER (11). ly 1 in 40,000 people worldwide and is the from nystagmus, strabismus, photophobia, Tyrosinase is also retained in the ER, due to most prevalent form of OCA among indi- and loss of visual acuity that can be severe unknown mechanisms, in OCA2 (12) and viduals of mixed European descent. OCA2 enough to render them legally blind (8). OCA3 (13), whereas in OCA4, tyrosinase affects 1 in 39,000 such individuals, with The highly visible OCA phenotype — exits the ER but is not correctly transported substantially higher prevalence in African- most dramatic in individuals with OCA1, to the melanosome (14). We have previously American and Amerindian populations. who have white hair, very pale skin, and demonstrated that ER retention of tyrosi- The carrier rate of a pathogenic deletion light-colored irides — is a source of sig- nase activates the unfolded protein response of OCA2 in African-American newborns is nificant emotional and psychological (UPR) (15), a highly conserved cell signaling estimated to be 1 in 235 (5); rates in some stress. Visual insufficiencies are often cascade that increases the capacity of a cell Amerindian populations reach 1 in 200 misinterpreted as intellectual deficits in to process misfolded proteins but can lead (6). OCA3 is rare, with notable frequency affected individuals, exacerbating feel- to apoptosis if ER stress is sustained. only in African populations (3). The inci- ings of alienation. A study of Nigerians The precise functions of the remaining with OCA2 found that they experienced OCA-related proteins (excepting tyrosi- Conflict of interest: In the past year, Seth J. Orlow alienation, avoided social interactions, nase) remain unclear. We have proposed served as a consultant to Astellas Pharmaceuticals, and were less emotionally stable. Further- that OCA2 mediates glutathione transport Bristol Myers Squibb, Galderma, Glaxo Smith Kline, Provectus Pharmaceuticals, and SkinMedica. more, affected individuals were less likely into the ER to promote disulfide bond Citation for this article: J Clin Invest. 2011; to complete schooling, find employment, formation during tyrosinase maturation 121(10):3828–3831. doi:10.1172/JCI59763. and find partners (9). (16) and that TYRP1 stabilizes tyrosinase 3828 The Journal of Clinical Investigation http://www.jci.org Volume 121 Number 10 October 2011 commentaries Figure 1 Synthesis and ER-based maturation of tyrosinase. Tyrosinase is synthesized on ribosomes and translocated into the ER membrane. (i) Tyrosi- nase is bound by the chaperones BiP, then calnexin (CNX), followed by ERp57 (ii) and calreticulin (CRT). Each chaperone is required to facilitate tyrosinase folding and glycosylation. In order to fold the peptide, protein disulfide isomerases (PDIs) such as ERp57 catalyze the formation of disulfide bonds. (iii) ERp57 is converted to a reduced state during catalysis. In order to recycle the protein, the ER oxidoreductin Ero1 oxidizes the PDI, generating ROS in the process. These ROS are detoxified by reduced glutathione (GSH), which is transported into the ER from the cytosol through a channel. Based on our studies (16), we hypothesize that the OCA2 protein serves as a GSH pump. (iv) ERp57 then catalyzes the isomerization of disulfide bonds to form a folded peptide. Correctly folded tyrosinase is released by the chaperones and then (v) recruited to a vesicle for transport to the Golgi. Recruitment may be facilitated by OCA2 and TYRP1. (vi) In the event that the protein is misfolded, disulfide bonds are removed by PDIs, which generates ROS that are removed by GSH, and tyrosinase is refolded. There are a limited number of protein refolding cycles, after which tyrosinase is transported to and degraded by proteasomes. GSSG, oxidized glutathione. (17). Costin et al. have proposed a role for TYR mutations can be improved by cultur- the melanocytes at the epidermal basal layer. the OCA4 protein, SLC45A2, in transport ing cells at temperatures of approximately Tyrosinase processing in cultured melano- of tyrosinase from Golgi to melanosomes, 31°C (11). In the early 1960s, long before cytes can be greatly improved by tyrosine, given that mutations in the SLC45A2 locus the tyrosinase-encoding gene was identi- DOPA (which is a cofactor for tyrosinase), result in trafficking of functional tyrosi- fied, researchers found that hair bulbs from and a variety of pH-altering agents, includ- nase to the plasma membrane (14). individuals with what we now call OCA-1A ing monensin
Load more

Recommended publications
  • Melanocytes and Their Diseases
    Downloaded from http://perspectivesinmedicine.cshlp.org/ on October 2, 2021 - Published by Cold Spring Harbor Laboratory Press Melanocytes and Their Diseases Yuji Yamaguchi1 and Vincent J. Hearing2 1Medical, AbbVie GK, Mita, Tokyo 108-6302, Japan 2Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892 Correspondence: [email protected] Human melanocytes are distributed not only in the epidermis and in hair follicles but also in mucosa, cochlea (ear), iris (eye), and mesencephalon (brain) among other tissues. Melano- cytes, which are derived from the neural crest, are unique in that they produce eu-/pheo- melanin pigments in unique membrane-bound organelles termed melanosomes, which can be divided into four stages depending on their degree of maturation. Pigmentation production is determined by three distinct elements: enzymes involved in melanin synthesis, proteins required for melanosome structure, and proteins required for their trafficking and distribution. Many genes are involved in regulating pigmentation at various levels, and mutations in many of them cause pigmentary disorders, which can be classified into three types: hyperpigmen- tation (including melasma), hypopigmentation (including oculocutaneous albinism [OCA]), and mixed hyper-/hypopigmentation (including dyschromatosis symmetrica hereditaria). We briefly review vitiligo as a representative of an acquired hypopigmentation disorder. igments that determine human skin colors somes can be divided into four stages depend- Pinclude melanin, hemoglobin (red), hemo- ing on their degree of maturation. Early mela- siderin (brown), carotene (yellow), and bilin nosomes, especially stage I melanosomes, are (yellow). Among those, melanins play key roles similar to lysosomes whereas late melanosomes in determining human skin (and hair) pigmen- contain a structured matrix and highly dense tation.
    [Show full text]
  • Natural Skin‑Whitening Compounds for the Treatment of Melanogenesis (Review)
    EXPERIMENTAL AND THERAPEUTIC MEDICINE 20: 173-185, 2020 Natural skin‑whitening compounds for the treatment of melanogenesis (Review) WENHUI QIAN1,2, WENYA LIU1, DONG ZHU2, YANLI CAO1, ANFU TANG1, GUANGMING GONG1 and HUA SU1 1Department of Pharmaceutics, Jinling Hospital, Nanjing University School of Medicine; 2School of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210002, P.R. China Received June 14, 2019; Accepted March 17, 2020 DOI: 10.3892/etm.2020.8687 Abstract. Melanogenesis is the process for the production of skin-whitening agents, boosted by markets in Asian countries, melanin, which is the primary cause of human skin pigmenta- especially those in China, India and Japan, is increasing tion. Skin-whitening agents are commercially available for annually (1). Skin color is influenced by a number of intrinsic those who wish to have a lighter skin complexions. To date, factors, including skin types and genetic background, and although numerous natural compounds have been proposed extrinsic factors, including the degree of sunlight exposure to alleviate hyperpigmentation, insufficient attention has and environmental pollution (2-4). Skin color is determined by been focused on potential natural skin-whitening agents and the quantity of melanosomes and their extent of dispersion in their mechanism of action from the perspective of compound the skin (5). Under physiological conditions, pigmentation can classification. In the present article, the synthetic process of protect the skin against harmful UV injury. However, exces- melanogenesis and associated core signaling pathways are sive generation of melanin can result in extensive aesthetic summarized. An overview of the list of natural skin-lightening problems, including melasma, pigmentation of ephelides and agents, along with their compound classifications, is also post‑inflammatory hyperpigmentation (1,6).
    [Show full text]
  • EXTENDED CARRIER SCREENING Peace of Mind for Planned Pregnancies
    Focusing on Personalised Medicine EXTENDED CARRIER SCREENING Peace of Mind for Planned Pregnancies Extended carrier screening is an important tool for prospective parents to help them determine their risk of having a child affected with a heritable disease. In many cases, parents aren’t aware they are carriers and have no family history due to the rarity of some diseases in the general population. What is covered by the screening? Genomics For Life offers a comprehensive Extended Carrier Screening test, providing prospective parents with the information they require when planning their pregnancy. Extended Carrier Screening has been shown to detect carriers who would not have been considered candidates for traditional risk- based screening. With a simple mouth swab collection, we are able to test for over 419 genes associated with inherited diseases, including Fragile X Syndrome, Cystic Fibrosis and Spinal Muscular Atrophy. The assay has been developed in conjunction with clinical molecular geneticists, and includes genes listed in the NIH Genetic Test Registry. For a list of genes and disorders covered, please see the reverse of this brochure. If your gene of interest is not covered on our Extended Carrier Screening panel, please contact our friendly team to assist you in finding a gene test panel that suits your needs. Why have Extended Carrier Screening? Extended Carrier Screening prior to pregnancy enables couples to learn about their reproductive risk and consider a complete range of reproductive options, including whether or not to become pregnant, whether to use advanced reproductive technologies, such as preimplantation genetic diagnosis, or to use donor gametes.
    [Show full text]
  • Dermatologic Manifestations of Hermansky-Pudlak Syndrome in Patients with and Without a 16–Base Pair Duplication in the HPS1 Gene
    STUDY Dermatologic Manifestations of Hermansky-Pudlak Syndrome in Patients With and Without a 16–Base Pair Duplication in the HPS1 Gene Jorge Toro, MD; Maria Turner, MD; William A. Gahl, MD, PhD Background: Hermansky-Pudlak syndrome (HPS) con- without the duplication were non–Puerto Rican except sists of oculocutaneous albinism, a platelet storage pool de- 4 from central Puerto Rico. ficiency, and lysosomal accumulation of ceroid lipofuscin. Patients with HPS from northwest Puerto Rico are homozy- Results: Both patients homozygous for the 16-bp du- gous for a 16–base pair (bp) duplication in exon 15 of HPS1, plication and patients without the duplication dis- a gene on chromosome 10q23 known to cause the disorder. played skin color ranging from white to light brown. Pa- tients with the duplication, as well as those lacking the Objective: To determine the dermatologic findings of duplication, had hair color ranging from white to brown patients with HPS. and eye color ranging from blue to brown. New findings in both groups of patients with HPS were melanocytic Design: Survey of inpatients with HPS by physical ex- nevi with dysplastic features, acanthosis nigricans–like amination. lesions in the axilla and neck, and trichomegaly. Eighty percent of patients with the duplication exhibited fea- Setting: National Institutes of Health Clinical Center, tures of solar damage, including multiple freckles, stel- Bethesda, Md (a tertiary referral hospital). late lentigines, actinic keratoses, and, occasionally, basal cell or squamous cell carcinomas. Only 8% of patients Patients: Sixty-five patients aged 3 to 54 years were di- lacking the 16-bp duplication displayed these findings.
    [Show full text]
  • Aberrant Colourations in Wild Snakes: Case Study in Neotropical Taxa and a Review of Terminology
    SALAMANDRA 57(1): 124–138 Claudio Borteiro et al. SALAMANDRA 15 February 2021 ISSN 0036–3375 German Journal of Herpetology Aberrant colourations in wild snakes: case study in Neotropical taxa and a review of terminology Claudio Borteiro1, Arthur Diesel Abegg2,3, Fabrício Hirouki Oda4, Darío Cardozo5, Francisco Kolenc1, Ignacio Etchandy6, Irasema Bisaiz6, Carlos Prigioni1 & Diego Baldo5 1) Sección Herpetología, Museo Nacional de Historia Natural, Miguelete 1825, Montevideo 11800, Uruguay 2) Instituto Butantan, Laboratório Especial de Coleções Zoológicas, Avenida Vital Brasil, 1500, Butantã, CEP 05503-900 São Paulo, SP, Brazil 3) Universidade de São Paulo, Instituto de Biociências, Departamento de Zoologia, Programa de Pós-Graduação em Zoologia, Travessa 14, Rua do Matão, 321, Cidade Universitária, 05508-090, São Paulo, SP, Brazil 4) Universidade Regional do Cariri, Departamento de Química Biológica, Programa de Pós-graduação em Bioprospecção Molecular, Rua Coronel Antônio Luiz 1161, Pimenta, Crato, Ceará 63105-000, CE, Brazil 5) Laboratorio de Genética Evolutiva, Instituto de Biología Subtropical (CONICET-UNaM), Facultad de Ciencias Exactas Químicas y Naturales, Universidad Nacional de Misiones, Felix de Azara 1552, CP 3300, Posadas, Misiones, Argentina 6) Alternatus Uruguay, Ruta 37, km 1.4, Piriápolis, Uruguay Corresponding author: Claudio Borteiro, e-mail: [email protected] Manuscript received: 2 April 2020 Accepted: 18 August 2020 by Arne Schulze Abstract. The criteria used by previous authors to define colour aberrancies of snakes, particularly albinism, are varied and terms have widely been used ambiguously. The aim of this work was to review genetically based aberrant colour morphs of wild Neotropical snakes and associated terminology. We compiled a total of 115 cases of conspicuous defective expressions of pigmentations in snakes, including melanin (black/brown colour), xanthins (yellow), and erythrins (red), which in- volved 47 species of Aniliidae, Boidae, Colubridae, Elapidae, Leptotyphlopidae, Typhlopidae, and Viperidae.
    [Show full text]
  • Colorado Birds | Summer 2021 | Vol
    PROFESSOR’S CORNER Learning to Discern Color Aberration in Birds By Christy Carello Professor of Biology at The Metropolitan State University of Denver Melanin, the pigment that results in the black coloration of the flight feathers in this American White Pelican, also results in stronger feathers. Photo by Peter Burke. 148 Colorado Birds | Summer 2021 | Vol. 55 No.3 Colorado Birds | Summer 2021 | Vol. 55 No.3 149 THE PROFESSOR’S CORNER IS A NEW COLORADO BIRDS FEATURE THAT WILL EXPLORE A WIDE RANGE OF ORNITHOLOGICAL TOPICS FROM HISTORY AND CLASSIFICATION TO PHYSIOLOGY, REPRODUCTION, MIGRATION BEHAVIOR AND BEYOND. AS THE TITLE SUGGESTS, ARTICLES WILL BE AUTHORED BY ORNI- THOLOGISTS, BIOLOGISTS AND OTHER ACADEMICS. Did I just see an albino bird? Probably not. Whenever humans, melanin results in our skin and hair color. we see an all white or partially white bird, “albino” In birds, tiny melanin granules are deposited in is often the first word that comes to mind. In feathers from the feather follicles, resulting in a fact, albinism is an extreme and somewhat rare range of colors from dark black to reddish-brown condition caused by a genetic mutation that or even a pale yellow appearance. Have you ever completely restricts melanin throughout a bird’s wondered why so many mostly white birds, such body. Many birders have learned to substitute the as the American White Pelican, Ring-billed Gull and word “leucistic” for “albino,” which is certainly a Swallow-tailed Kite, have black wing feathers? This step in the right direction, however, there are many is due to melanin.
    [Show full text]
  • Preconception Carrier Screening
    Focusing on Personalised Medicine PRECONCEPTION CARRIER SCREENING Preconception carrier screening is an important tool for prospective parents to help them determine their risk of having a child affected with a heritable disease. In many cases, parents aren’t aware they are carriers and have no family history due to the rarity of some diseases in the general population. What is covered by the screening? Our Inherited Disease Panel tests over 300 genes associated with more than 700 unique commonly inherited diseases, including common forms of inherited deafness, blindness, heart disease, Parkinson’s disease, immunodeficiency, and various ataxias, anaemias, and treatable metabolic syndromes. The assay has been developed in conjunction with clinical molecular geneticists, and includeds genes listed in the NIH Genetic Test Registry. For a full list of genes and disorders covered, please see the reverse of this brochure. Why have Preconception Carrier Screening? Carrier screening prior to pregnancy enables couples to learn about their reproductive risk and consider a complete range of reproductive options, including whether or not to become pregnant, whether to use advanced reproductive technologies, such as preimplantation genetic diagnosis, or use donor gametes. Screening also allows couples to consider prenatal diagnosis and pregnancy management options in the event of an affected fetus. Whilst individually each disease tested is rare, around 25% of people will carry at least one abnormal mutation. These disorders are usually autosomal recessive, which means that a child must inherit a defective gene from each parent to have the disease. For autosomal recessive conditions, if a person is a carrier of the disease, they have one defective copy of the gene and one normal copy and typically don’t have any symptoms of the disease.
    [Show full text]
  • Amino Acid Disorders
    471 Review Article on Inborn Errors of Metabolism Page 1 of 10 Amino acid disorders Ermal Aliu1, Shibani Kanungo2, Georgianne L. Arnold1 1Children’s Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; 2Western Michigan University Homer Stryker MD School of Medicine, Kalamazoo, MI, USA Contributions: (I) Conception and design: S Kanungo, GL Arnold; (II) Administrative support: S Kanungo; (III) Provision of study materials or patients: None; (IV) Collection and assembly of data: E Aliu, GL Arnold; (V) Data analysis and interpretation: None; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. Correspondence to: Georgianne L. Arnold, MD. UPMC Children’s Hospital of Pittsburgh, 4401 Penn Avenue, Suite 1200, Pittsburgh, PA 15224, USA. Email: [email protected]. Abstract: Amino acids serve as key building blocks and as an energy source for cell repair, survival, regeneration and growth. Each amino acid has an amino group, a carboxylic acid, and a unique carbon structure. Human utilize 21 different amino acids; most of these can be synthesized endogenously, but 9 are “essential” in that they must be ingested in the diet. In addition to their role as building blocks of protein, amino acids are key energy source (ketogenic, glucogenic or both), are building blocks of Kreb’s (aka TCA) cycle intermediates and other metabolites, and recycled as needed. A metabolic defect in the metabolism of tyrosine (homogentisic acid oxidase deficiency) historically defined Archibald Garrod as key architect in linking biochemistry, genetics and medicine and creation of the term ‘Inborn Error of Metabolism’ (IEM). The key concept of a single gene defect leading to a single enzyme dysfunction, leading to “intoxication” with a precursor in the metabolic pathway was vital to linking genetics and metabolic disorders and developing screening and treatment approaches as described in other chapters in this issue.
    [Show full text]
  • Oculocutaneous Albinism: an African Perspective
    Br Ir Orthopt J 2014; 11: 3–8 Oculocutaneous albinism: an African perspective GERALDINE R. McBRIDE1,2 MSc 1Orthoptic Department, Eye Clinic, University Hospital Galway, Galway, Ireland 2Kwale District Eye Centre, Kwale, Mombasa, Kenya Abstract behind OCA, and explore OCA in an African context in terms of the effects on the health and education of Aim: To describe the genetics behind oculocutaneous individuals with OCA. The outcome of this review will albinism (OCA), and explore OCA in an African be to provide useful advice to those with OCA and those context in terms of the effects on the health and working with or teaching students with OCA. education of individuals with OCA. Methods: A literature-based review was conducted using Pubmed. Searches were restricted to English- Genetics based publications, focusing on OCA in Africa. There are four different types of OCA, which result from Results: The genetics behind OCA and the effects of a mutation in one of several genes (Table 1).1,2,4 Each of OCA in terms of visual impairment and skin cancer these genes is chemically coded to produce proteins are explained along with a description of what low which are involved in the production of melanin. The vision services and low vision aids are available to mutation can result in the reduction of melanin pro- those with OCA in Africa. duction, or no melanin production.1 All four types of Conclusions: The review concludes with useful advice OCA are autosomal recessive. Therefore if both parents to those with OCA and those working with or are carriers of the mutated gene there is a 25% chance of teaching students with OCA.
    [Show full text]
  • Oculocutaneous Albinism, a Family Matter Summer Moon, DO,* Katherine Braunlich, DO,** Howard Lipkin, DO,*** Annette Lacasse, DO***
    Oculocutaneous Albinism, A Family Matter Summer Moon, DO,* Katherine Braunlich, DO,** Howard Lipkin, DO,*** Annette LaCasse, DO*** *Dermatology Resident, 3rd year, Botsford Hospital Dermatology Residency Program, Farmington Hills, MI **Traditional Rotating Intern, Largo Medical Center, Largo, FL ***Program Director, Botsford Hospital Dermatology Residency Program, Farmington Hills, MI Disclosures: None Correspondence: Katherine Braunlich, DO; [email protected] Abstract Oculocutaneous albinism (OCA) is a group of autosomal-recessive conditions characterized by mutations in melanin biosynthesis with resultant absence or reduction of melanin in the melanocytes. Herein, we present a rare case of two Caucasian sisters diagnosed with oculocutaneous albinism type 1 (OCA1). On physical exam, the sisters had nominal cutaneous evidence of OCA. This case highlights the difficulty of diagnosing oculocutaneous albinism in Caucasians. Additionally, we emphasize the uncommon underlying genetic mutations observed in individuals with oculocutaneous albinism. 2,5 Introduction people has one of the four types of albinism. of exon 4. Additionally, patient A was found to Oculocutaneous albinism (OCA) is a group of We present a rare case of sisters diagnosed with possess the c.21delC frameshift mutation in the autosomal-recessive conditions characterized by oculocutaneous albinism type 1, emphasizing the C10orf11 gene. Patient B was found to possess the mutations in melanin biosynthesis with resultant uncommon genetic mutations we observed in these same heterozygous mutation and deletion in the two individuals. absence or reduction of melanin in the melanocytes. Figure 1 Melanin-poor, pigment-poor melanocytes phenotypically present as hypopigmentation of the Case Report 1,2 Two Caucasian sisters were referred to our hair, skin, and eyes. dermatology clinic after receiving a diagnosis of There are four genes responsible for the four principal oculocutaneous albinism type 1.
    [Show full text]
  • Albinism: Modern Molecular Diagnosis
    British Journal of Ophthalmology 1998;82:189–195 189 Br J Ophthalmol: first published as 10.1136/bjo.82.2.189 on 1 February 1998. Downloaded from PERSPECTIVE Albinism: modern molecular diagnosis Susan M Carden, Raymond E Boissy, Pamela J Schoettker, William V Good Albinism is no longer a clinical diagnosis. The past cytes and into which melanin is confined. In the skin, the classification of albinism was predicated on phenotypic melanosome is later transferred from the melanocyte to the expression, but now molecular biology has defined the surrounding keratinocytes. The melanosome precursor condition more accurately. With recent advances in arises from the smooth endoplasmic reticulum. Tyrosinase molecular research, it is possible to diagnose many of the and other enzymes regulating melanin synthesis are various albinism conditions on the basis of genetic produced in the rough endoplasmic reticulum, matured in causation. This article seeks to review the current state of the Golgi apparatus, and translocated to the melanosome knowledge of albinism and associated disorders of hypo- where melanin biosynthesis occurs. pigmentation. Tyrosinase is a copper containing, monophenol, mono- The term albinism (L albus, white) encompasses geneti- oxygenase enzyme that has long been known to have a cally determined diseases that involve a disorder of the critical role in melanogenesis.5 It catalyses three reactions melanin system. Each condition of albinism is due to a in the melanin pathway. The rate limiting step is the genetic mutation on a diVerent chromosome. The cutane- hydroxylation of tyrosine into dihydroxyphenylalanine ous hypopigmentation in albinism ranges from complete (DOPA) by tyrosinase, but tyrosinase does not act alone.
    [Show full text]
  • A Neuroendocrine Theory for the Etiology of Vitiligo
    Cush ZM, J Med Stud Res 2018, 1: 007 DOI: 10.24966/MSR-5657/100007 HSOA Journal of Medicine: Study & Research Research Article of the skin, the melanocytes. The triggers, which range from sunburn A Neuroendocrine Theory for to mechanical trauma and chemical exposures, ultimately cause an autoimmune response those targets melanocytes, driving progressive the Etiology of Vitiligo skin depigmentation [3]. Zakiya M Cush* The New York Medical College, Valhalla, New York, USA Figure 1: Vitiligo is a condition in which the skin loses its pigment cells (melanocytes). This can result in discolored patches in different areas of the body, including the skin, hair, retina and mucous membranes [2]. Biochemistry of melanin formation Abstract According to published research, the adenylate cyclase signaling It has long been believed that vitiligo is an autoimmune disease. pathway, the stimulation of protein kinase C via DAG and the ty- And while there are many theories of this disease process, which rosine kinase activity mechanism (Figure 2) are responsible for the include cytotoxic and hereditary, there is another approach, which proliferation of melanocytes in mammals [4]. has yet to be considered. This paper will present a neuroendocrine hypothesis to why vitiligo occurs. With the understanding of the ty- rosinase enzyme, tyrosine kinase activity, and the Melanocytic Stim- ulating Hormone (MSH-α) and its effect on melanocyte production, an alternative approach to vitiligo should be considered, and it be- gins in the brain. Introduction What is vitiligo? Vitiligo is an acquired cutaneous disorder of pigmentation, with an incidence of 0.5% to 2% worldwide which, manifests as white mac- ules on the skin (Figure 1) and can cause significant psychological stress and stigmatization [1,2].
    [Show full text]