Oculocutaneous albinism

Genetic variants in melanogenesis proteins TYRP1 and TYR are associated with the golden rhesus macaque phenotype

Nonhuman primates (NHPs) are vital translational research models due to their high genetic, physiological, and anatomical homology with humans. The "golden" rhesus macaque (Macaca mulatta) phenotype is a naturally occurring, inherited trait with a visually distinct pigmentation pattern resulting in light blonde colored fur. Retinal imaging also reveals consistent hypopigmentation and occasional foveal hypoplasia. Here, we describe the use of genome-wide association in 2 distinct NHP populations to identify candidate variants in genes linked to the golden phenotype. Two missense variants were identified in the Tyrosinase-related protein 1 gene (Asp343Gly and Leu415Pro) that segregate with the phenotype. An additional and distinct association was also found with a Tyrosinase variant (His256Gln), indicating the light-colored fur phenotype can result from multiple genetic mechanisms. The implicated genes are related through their contribution to the melanogenesis pathway. Variants in these 2 genes are known to cause pigmentation phenotypes in other species and to be associated with oculocutaneous albinism in humans. The novel associations presented in this study will permit further investigations into the role these proteins and variants play in the melanogenesis pathway and model the effects of genetic hypopigmentation and altered melanogenesis in a naturally occurring nonhuman primate model.

Ophthalmological Manifestations of Oculocutaneous and Ocular Albinism: Current Perspectives

Albinism describes a heterogeneous group of genetically determined disorders characterized by disrupted synthesis of melanin and a range of developmental ocular abnormalities. The main ocular features common to both oculocutaneous albinism (OCA), and ocular albinism (OA) include reduced visual acuity, refractive errors, foveal hypoplasia, congenital nystagmus, iris and fundus hypopigmentation and visual pathway misrouting, but clinical signs vary and there is phenotypic overlap with other pathologies. This study reviews the prevalence, genetics and ocular manifestations of OCA and OA, including abnormal development of the optic chiasm. The role of visual electrophysiology in the detection of chiasmal dysfunction and visual pathway misrouting is emphasized, highlighting how age-associated changes in visual evoked potential (VEP) test results must be considered to enable accurate diagnosis, and illustrated further by the inclusion of novel VEP data in genetically confirmed cases. Differential diagnosis is considered in the context of suspected retinal and other disorders, including rare syndromes that may masquerade as albinism.

In vitro disease modeling of oculocutaneous albinism type 1 and 2 using human induced pluripotent stem cell-derived retinal pigment epithelium

Oculocutaneous albinism (OCA) encompasses a set of autosomal recessive genetic conditions that affect pigmentation in the eye, skin, and hair. OCA patients display reduced best-corrected visual acuity, reduced to absent ocular pigmentation, abnormalities in fovea development, and/or abnormal decussation of optic nerve fibers. It has been hypothesized that improving eye pigmentation could prevent or rescue some of the vision defects. The goal of the present study was to develop an in vitro model for studying pigmentation defects in human retinal pigment epithelium (RPE). We developed a “disease in a dish” model for OCA1A and OCA2 types using induced pluripotent stem cells to generate RPE. The RPE is a monolayer of cells that are pigmented, polarized, and polygonal in shape, located between the neural retina and choroid, with an important role in vision. Here we show that RPE tissue derived in vitro from OCA patients recapitulates the pigmentation defects seen in albinism, while retaining the apical-basal polarity and normal polygonal morphology of the constituent RPE cells.

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We established a human iPSC-based in vitro model for oculocutaneous albinism (OCA)

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iRPE derived from OCA-iPSC retains apical-basal polarity and polygonal morphology

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OCA-iRPE recapitulates the pigmentation defect seen in albinism

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Excess pre-melanosomes and scarce mature melanosomes are found in OCA-iRPE

Factors Associated with Skin Cancers in People with Albinism in Togo

Objective

The aim of this study was to identify the factors associated with skin cancers in people with albinism (PWA) in Togo.

Method

This is a retrospective analytical study of the records of PWA examined during five dermatological consultation campaigns from 2019 to 2021.

Results

During the study period, 517 PWA were seen. Sixty-four (12.3%) of these PWA had presented with 137 cases of skin cancer. The sex ratio (M/F) was 0.9. The average age of PWA with skin cancer was 39.69 ± 15.61 years and that of PWA without skin cancer was 19.17 ± 15.24 years (p ≤ 0.001). The 137 cases of skin cancers were dominated by basal cell carcinomas (45.9%). These skin cancers were located preferentially in the cephalic region (77 cases; 56.2%), followed by the upper limbs (33 cases; 24.1%). In multivariate analysis, the risk factors for skin cancers in PWA were age over 39 years (p ≤ 0.001) and the presence of actinic keratoses (p ≤ 0.001). In contrast, the presence of ephelides (p=0.018) was a protective factor.

Conclusion

This study confirms that advanced age and actinic keratoses are risk factors for skin cancer in PWA, in connection with the cumulative role of solar radiation. Its originality lies in the identification of ephelides as a protective factor. The knowledge and consideration of these risk factors will make it possible to optimise strategies for the prevention of skin cancers in PWA.

Management of albinism: French guidelines for diagnosis and care

Albinism is a worldwide genetic disorder caused by mutations in at least 20 genes, identified to date, that affect melanin production or transport in the skin, hair and eyes. Patients present with variable degrees of diffuse muco-cutaneous and adnexal hypopigmentation, as well as ocular features including nystagmus, misrouting of optic nerves and foveal hypoplasia. Less often, albinism is associated with blood, immunological, pulmonary, digestive and/or neurological anomalies. Clinical and molecular characterizations are essential in preventing potential complications. Disease-causing mutations remain unknown for about 25% of patients with albinism. These guidelines have been developed for the diagnosis and management of syndromic and non-syndromic forms of albinism, based on a systematic review of the scientific literature. These guidelines comprise clinical and molecular characterization, diagnosis, therapeutic approach and management.

Management of aggressive posterior retinopathy of prematurity in oculocutaneous albinism

A male infant, born preterm at 32 weeks of gestation, was referred at 36-week postmenstrual age for retinopathy of prematurity (ROP) screening. He had nystagmus, generalised hypopigmentation of skin, hair and eyes with preaxial polydactyly. The fundus was depigmented with prominently visible choroidal vessels. The retinal vessels were dilated, tortuous at zone 1. There was presence of arcading, shunting of vessels with presence of vitreous haemorrhage in the left eye. A diagnosis of aggressive posterior retinopathy of prematurity (APROP) in association with oculocutaneous albinism (OCA) was made.Half-dose intravitreal bevacizumab was used to treat the vascular condition. After 2 weeks, there was complete regression of APROP with a completely mature retina observed at 4 months post-treatment. Herein, we describe the role of red-free light for screening ROP in infants with OCA; challenges in the management of ROP with laser photocoagulation compared with intravitreal anti-vascular endothelial growth factor therapy.

[Photocarcinogenesis-molecular mechanisms and practical relevance]

Ultraviolet (UV) radiation is the main risk factor for the development of melanocytic and nonmelanocytic skin cancer. UVA and UVB radiation are of particular importance in photocarcinogenesis. Depending on the wavelength, mechanisms of tumor initiation and promotion include direct DNA damage and proinflammatory processes. In recent years, the number of skin cancer cases in Germany has continuously increased. In addition to regular skin check-ups, use of suitable textile protection and sunscreens play a central role in the prevention of cancer development. As dermatologists, it is our task to regularly inform our patients about the consequences of excessive sun exposure and to adequately inform them about necessary protective devices.

The metabolic profile of Asinara (albino) and Sardo donkeys (pigmented) (Equus asinus L., 1758) points to unequivocal breed assignment of individuals

This study pointed to explore if variations in circulating levels of metabolites in the blood stream of no. 25 feral donkeys occur in view of the different coat color between specimens of Asinara (albino, no. 8) vs. Sardo (dun-grey, no. 17) breed. All individuals involved in this investigation are living in the nature, at Mediterranean latitudes and roam in the same areas all over the National Park of Capo Caccia, where they feed on spontaneous vegetation sources. The study was conducted during the positive photoperiod of the boreal hemisphere (peak in the month of June, 2019) to maximize the effect of exposure to the natural sun radiation and thus elicit the coping ability of albino (Asinara) in comparison with pigmented donkeys (Sardo). The biochemical profile of all donkeys was used in a Discriminant Analysis (DA) to explore if circulating levels of metabolites could point to metabolic markers for breed assignment of individuals following a canonical discriminant analysis (CANDISC). The biochemical investigation included also the determination of the circulating Vitamin E (alpha tocopherol, α-TOH), as an essential biologically active compound involved in antioxidant mechanisms, and its respective status (circulating α-TOH to total triglycerides and total cholesterol ratio). In the CANDISC, the distance between the two breeds was not significant. However, it pointed to different metabolites (UREA, total protein, total triglycerides, Zn) capable of describing biochemical patterns on each respective breed (Asinara vs. Sardo). The multivariate analysis DA carried out using 22 metabolites correctly assigned individuals to the two breeds in the 100% of cases. In view of such metabolic background, circulating α-TOH found in the bloodstream of Asinara vs. Sardo donkeys under free grazing conditions turned out to reach similar values (2.114 vs. 1.872 µg/ml, respectively, p = 0.676). It is worth noting that significant differences were observed as to circulating lactate dehydrogenase (LDH, p = 0.022) levels, in association with increased creatine phosphokinase (CPK, p = 0.076), both above the upper limit of the physiological range reported in other donkey breeds, and found in the totality of Asinara (albino) donkeys solely, still apparently clinically healthy.

Therapeutics of premature hair graying: A long journey ahead

Premature graying of hair has major psychosocial and socioeconomic repercussion, as it is considered as a sign of hastily progressing old age, ill health and often leads to loss of self-esteem. Hair is said to gray prematurely when it happens before the age of 20 years in Caucasians, 25 years in Asians, and 30 years in Africans. The hair color chiefly depends on melanin pigment, and fabrication of this pigment takes place in melanosomes through the process of melanogenesis. This complex biochemical pathway (melanogenesis) is further dependent on tyrosinase which acts as fuel.The normal human scalp is subjected to various factors categorized as intrinsic and extrinsic leading to graying of hair. Intrinsic factors comprise of variants responsible for changes at genetic level while extrinsic factors include air pollution, ultraviolet radiation, smoking, and nutrition. It has been proposed that direct or indirect effect of all these factors results in the generation of reactive oxygen species (ROS), thus leading to further damage. Though research has expanded in last few years in terms of microscopic, biochemical (hormonal, enzymatic), and molecular changes happening within hair follicle/shaft, still the exact mechanism leading to premature graying of hair is not well understood. Probable solutions toward this quandary are diet, herbal remedies, and temporary hair colorants. Ironically, the latter one being the most common has various side effects such as allergic reactions, inflammation, and hair loss. The aim of this paper was to review the manifestation and probable future interventions in preventing premature hair graying.

Albinism: epidemiology, genetics, cutaneous characterization, psychosocial factors

Oculocutaneous albinism is an autosomal recessive disease caused by the complete absence or decrease of melanin biosynthesis in melanocytes. Due to the reduction or absence of melanin, albinos are highly susceptible to the harmful effects of ultraviolet radiation and are at increased risk of actinic damage and skin cancer. In Brazil, as in other parts of the world, albinism remains a little known disorder, both in relation to epidemiological data and to phenotypic and genotypic variation. In several regions of the country, individuals with albinism have no access to resources or specialized medical care, and are often neglected and deprived of social inclusion. Brazil is a tropical country, with a high incidence of solar radiation during the year nationwide. Consequently, actinic damage and skin cancer occur early and have a high incidence in this population, often leading to premature death. Skin monitoring of these patients and immediate therapeutic interventions have a positive impact in reducing the morbidity and mortality associated with this condition. Health education is important to inform albinos and their families, the general population, educators, medical professionals, and public agencies about the particularities of this genetic condition. The aim of this article is to present a review of the epidemiological, clinical, genetic, and psychosocial characteristics of albinism, with a focus in skin changes caused by this rare pigmentation disorder.

Dermatological and Epidemiological Profiles of Patients with Albinism in São Paulo, Brazil, between 2010 and 2017: A Cross-Sectional Study

INTRODUCTION

Oculocutaneous albinism is an autosomal recessive disease caused by complete absence of or decrease in melanin biosynthesis in melanocytes. Due to the reduction or absence of melanin, albinos are highly susceptible to the harmful effects of ultraviolet radiation and are at greater risk of actinic damage and skin cancer. There are no epidemiological data on the incidence of albinism in Brazil.

OBJECTIVE

To analyze the clinical and epidemiological profile of patients with albinism treated by the Pró-Albino Program of the Dermatology Clinic of Santa Casa de Misericórdia from its beginning in 2010 until 2017.

METHODS

In this cross-sectional study, the records of all consecutive albino patients admitted to the service in the study period were reviewed. Sociodemographic data, family history, and dermatological clinical data were collected.

RESULTS

Between March 2010 and April 2017, 191 patients were admitted, of whom 109 were female (57.07%) and the age range was 0-92 years, with >30% under the age of 18 years. Consanguinity among the parents was confirmed by 26% of the patients. Unprotected sun exposure was reported by 109 (57.07%), and 138 (72.25%) had a history of sunburn. Of the 146 records with information, 38 had skin cancer (26%), with a mean age of 47.4 (p < 0.0001); the youngest patient diagnosed with a cutaneous tumor was 23 years old. The prevalence of actinic damage was high. There was information on solar elastosis and actinic keratosis in 148 medical records, of which 96 (64.8%) patients had elastosis and 75 (50.67%) keratoses. Elastosis, keratosis, and skin cancer were significantly associated with age, unprotected sun exposure, and sunburn (p < 0.05). Of the 37 (26% of the sample of 146) patients with a previous or current history of skin cancer, it was possible to identify the histological type in 29 (13 men and 16 women); of these, 18 (62%) were basal cell carcinomas (BCC), 15 (51%) were squamous cell carcinomas (SCC), and 2 (7%) were melanomas. Of these, 4 cases (14%) presented the 2 types of carcinoma (BCC and SCC), and the 2 that had a diagnosis of melanoma also had BCC. Some patients had multiple ulcerated tumors. The tumor site was preferentially in the head and neck (43%), trunk (37%) and limbs (20%).

CONCLUSIONS

Albinos represent a risk group for skin cancer and other actinic lesions. These lesions were found to be prevalent in the albinos seen by the program and probably reflect the characteristics found in the Brazilian albino population. Access to health care, especially through multidisciplinary programs that enable the diagnosis and early treatment of these lesions, health education, and the use of photoprotective measures can reduce morbidity and mortality and improve the quality of life of patients with this rare genetic condition.

[Oculocutaneous and ocular albinism]

Albinism can be divided into oculocutaneous albinism (OCA) and ocular albinism (OA). In the differential diagnostics these can be distinguished from rarer syndromes with partial albinism, which are frequently associated with susceptibility to infections and neurological symptoms. The OCA is an autosomal recessive inherited disease of melanin biosynthesis, which leads to complete or partial loss of melanin in the skin, hair follicles and eyes. Of the seven currently known subtypes (OCA 1-7), four are well-characterized (OCA 1-4). These are based on gene mutations, which code for tyrosinase, a key enzyme in melanin synthesis and for further proteins. These play an important role in the catalytic activity of tyrosinase and the structure and function of melanosomes. In the presence of these subtypes, the clinical symptoms and the course of the disease show a pronounced variability, especially in the type and extent of pigmentation of the skin and hair as well as the severity of eye involvement, which makes the phenotypic classification difficult. Treatment priorities are a consistent protection from UV light for prophylaxis against skin cancer and regular preventive investigations. The ocular alterations typical for albinism necessitate timely diagnostics and care by institutions specialized in ophthalmology. Novel strategies for systemic treatment of subtypes of albinism are in preclinical testing. The OA without skin involvement shows X‑linked inheritance, is much rarer and is characterized by reduced pigmentation of the retina and iris, nystagmus and macular hypoplasia, sometimes with substantial loss of visual acuity. The typical ocular symptoms of OA can be manifested to a varying extent in all forms of OCA.

Amelanotic Ciliochoroidal Melanoma in a Patient with Oculocutaneous Albinism

To report a case of amelanotic ciliochoroidal melanoma in a patient with oculocutaneous albinism. A 76-year-old Caucasian male with a past medical history of oculocutaneous albinism and recurrent urothelial carcinoma was found to have a mass in the left eye, suspicious for ciliochoroidal melanoma. On examination, visual acuity was 20/400 in both eyes (OU). External examination showed iris transillumination defects. Funduscopic examination OU revealed blonde fundus, optic nerve hypoplasia, and foveal hypoplasia, confirmed on optical coherence tomography. Funduscopic examination of the left eye revealed an inferonasal amelanotic ciliochoroidal mass, measuring 12.0 mm × 13.0 mm × 8.8 mm. There was visible intrinsic tumor vasculature and overlying subretinal fluid. B-scan ultrasonography demonstrated a hypoechoic, dome-shaped mass. The clinical and imaging features were consistent with amelanotic ciliochoroidal melanoma. The patient was treated with iodine-125 plaque radiotherapy. At the 4-month follow-up, the tumor demonstrated regression from 8.8 mm to 3.2 mm in thickness. Despite the apparent lack of uveal pigmentation, patients with oculocutaneous albinism can develop uveal melanoma.

Blood serum retinol levels in Asinara white donkeys reflect albinism-induced metabolic adaptation to photoperiod at Mediterranean latitudes

Previous works on albinism form of Asinara white donkeys (Equus asinus) identified the mutation leading to the peculiar phenotype spread to all specimens of the breed. Inbreeding naturally occurred under geographic isolation, on Asinara Island, in the Mediterranean Sea. Albino individuals can be more susceptible to develop health problems when exposed to natural sun radiation. Alternative metabolic pathways involved in photoprotection were explored in this trial. Nutrition‐related metabolites are believed to contribute to the conservation of Asinara donkeys, in which melanin, guaranteeing photoprotection, is lacking. Biochemical profiles with particular focus on blood serum β‐carotene and retinol levels were monitored. Identical natural grazing conditions for both Asinara (albino) and Sardo (pigmented) donkey breeds were assured on same natural pastures throughout the experimental period. A comparative metabolic screening, with emphasis on circulating retinol and nutrient‐related metabolites between the two breeds, was carried out over one year. Potential intra‐ and interspecimen fluctuations of metabolites involved in photoprotection were monitored, both during negative and positive photoperiods. Differences (p = .064) between blood serum concentrations of retinol from Asinara versus Sardo breed donkeys (0.630 vs. 0.490 μg/ml, respectively) were found. Retinol levels of blood serum turned out to be similar in the two groups (0.523 vs. 0.493 μg/ml, respectively, p = .051) during the negative photoperiod, but markedly differed during the positive one (0.738 vs. 0.486, respectively, p = .016). Blood serum β‐carotene levels displayed to be constantly around the limit of sensitivity in all animals of both breeds. Variations in blood serum concentrations of retinol in Asinara white donkeys can reflect the need to cope with seasonal exposure to daylight at Mediterranean latitudes, as an alternative to the lack of melanin. These results may suggest that a pulsed mobilization of retinol from body stores occurs to increase circulating levels during positive photoperiod.

A Case of a Newborn with Agenesis of the Corpus Callosum Complicated with Ocular Albinism

Purpose

To report a case of ocular albinism found in a newborn infant in whom agenesis of the corpus callosum (ACC) was indicated in utero.

Case Report

This study involved a female newborn who was delivered after a gestational period of 41 weeks. The patient was referred to the Obstetrics Department at Takatsuki Hospital, Takatsuki City, Japan, after the indication of ACC by magnetic resonance imaging (MRI) at a nearby clinic during the fetal period. At birth, the baby's weight was 2,590 g, and ACC and ventricular enlargement were found by cranial sonography and cranial MRI. While initial ophthalmic findings noted partial loss of pigmentation of the iris and hypopigmentation of broad areas of the fundus in both eyes, nystagmus was not observed. The patient's hair pigment was slightly diluted, and the color of her skin was slightly off-white. At 2 years after birth, obvious mental retardation was observed. With regard to other systemic findings, no apparent heart, kidney, or immune system abnormalities were found.

Conclusion

Although the patient in question is presently growing without any major systemic problems, it will be necessary in the future to pay attention to any changes in systemic and ophthalmic findings.

Quality of life in patients with oculocutaneous albinism

BACKGROUND

The social reality of the albino needs to be more studied in Brazil, as myths and social segregation regarding this illness are likely to be found in the country, with psychosocial and medical implications.

OBJECTIVE

As this subject has not been referenced in previous scientific articles in Brazil, this research intends to evaluate the quality of life of the albinos that treated at our medical institution.

METHODS

The quality of life was evaluated through the WHOQOL-BREF. Furthermore, two aspects of main relevance in the lives of the albinos were also objects of research, low vision and skin cancer. The sample consisted of forty oculocutaneous albinos and a control group of forty healthy individuals, matched by sex and age.

RESULTS

Among the participants, 57.7% were between 18 and 40 years old, 28.2% were between 41 and 60, and 14.1% were over 60. 42.1% had skin cancer before the study, 18.4% had skin cancer during the study and 89.5% stated visual deficit. The results obtained in the questionnaires showed a statistically significant difference in the physical domain, with P < 0.001.

CONCLUSION

Low vision combined with skin lesions and social stigma may contribute to disturbances in the quality of life of oculocutaneous albinos. The results presented in this study demonstrated the vulnerability of the affected individuals and the special care required by those patients, at the same time that the need for further research is highlighted in order to better elucidate the aspects related to albinism.

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Nano-scale morphology of melanosomes revealed by small-angle X-ray scattering

Melanosomes are highly specialized organelles that produce and store the pigment melanin, thereby fulfilling essential functions within their host organism. Besides having obvious cosmetic consequences – determining the color of skin, hair and the iris – they contribute to photochemical protection from ultraviolet radiation, as well as to vision (by defining how much light enters the eye). Though melanosomes can be beneficial for health, abnormalities in their structure can lead to adverse effects. Knowledge of their ultrastructure will be crucial to gaining insight into the mechanisms that ultimately lead to melanosome-related diseases. However, due to their small size and electron-dense content, physiologically intact melanosomes are recalcitrant to study by common imaging techniques such as light and transmission electron microscopy. In contrast, X-ray-based methodologies offer both high spatial resolution and powerful penetrating capabilities, and thus are well suited to study the ultrastructure of electron-dense organelles in their natural, hydrated form. Here, we report on the application of small-angle X-ray scattering – a method effective in determining the three-dimensional structures of biomolecules – to whole, hydrated murine melanosomes. The use of complementary information from the scattering signal of a large ensemble of suspended organelles and from single, vitrified specimens revealed a melanosomal sub-structure whose surface and bulk properties differ in two commonly used inbred strains of laboratory mice. Whereas melanosomes in C57BL/6J mice have a well-defined surface and are densely packed with 40-nm units, their counterparts in DBA/2J mice feature a rough surface, are more granular and consist of 60-nm building blocks. The fact that these strains have different coat colors and distinct susceptibilities to pigment-related eye disease suggest that these differences in size and packing are of biological significance.

The pleiotropic roles of autophagy regulators in melanogenesis

Melanin pigments protect the skin and eyes from toxic insults and are critical for the normal functioning of multiple organ systems including the skin, eyes, and brain. Biochemical and genetic studies in both human and mice have revealed the molecular machinery controlling the transcription of genes encoding enzymes that produce melanin and the trafficking of these enzymes to the melanosome, a lysosome-related organelle dedicated to melanin synthesis. Recent functional genomic studies have identified a role for genes previously known to regulate autophagy, a cellular process that facilitates nutrient recycling during starvation, in the biogenesis of melanosomes in vitro and in vivo. In this review, we describe the pleiotropic roles of autophagy regulators in multiple vesicle trafficking processes, define a specific role for autophagy regulators in melanosome biogenesis, and shed light on how autophagy and autophagy regulators may play different roles in both the biogenesis of melanosomes and melanosome destruction.

Case report: a black and white twin

Albinism is an autosomal recessive disorder that is caused by a defective synthesis of melanin, resulting in a generalized reduction of pigmentation in the skin, hair and eyes, and leading to an increased risk of skin cancer and vision problems. We report a case of a 22-year-old primigravida of Negroid origin who delivered dichorial diamniotic twins: two daughters were born with a totally different appearance. The first child had a light brown skin, black curly hair and brown eyes, whereas the second had a striking white skin, red-blond curly hair and blue eyes. Oculocutaneous albinism (OCA) and heteropaternal superfecundation were considered in the differential diagnosis. Genetic testing confirmed the diagnosis of OCA type 2 in the second child. The diagnosis of albinism has clinical implications and must be considered when a black and white twin is born.

L-DOPA is an endogenous ligand for OA1

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.

Lack of adequate sun protection for children with oculocutaneous albinism in South Africa

BACKGROUND

Childhood is a high risk time for ultraviolet induced skin damage as this age group has more time and opportunity to be outdoors in the sun. Children in Africa with the inherited condition oculocutaneous albinism (OCA) are especially vulnerable due to their lack of protective melanin. They are highly susceptible to developing skin lesions that have both cosmetic and health complications, with a high risk of developing skin cancers. The study aimed to explore the adequacy of sun protection strategies of children with albinism in order to inform future provision.

METHODS

Community based participatory research methods were employed to investigate sun protection strategies in 90 pupils with OCA (40 female and 50 male) boarding at a special school educating pupils with visual impairment in a rural area of northern South Africa. Hats worn and sunscreen preparations used were examined during semi-structured face to face interviews conducted in small peer groups. The resident nurse interpreted if necessary and provided additional information on monitoring and treatment of skin lesions.

RESULTS

Participants with albinism in this study were exposed to high levels of ultraviolet radiation throughout the year and showed skin damage despite wearing protective head gear. All except one pupil possessed at least one hat, with a mean brim width of 5.4 cm. Gender differences in sun avoidance behaviour were documented, with females seeking shade during recreational periods and males playing soccer outside. Although 38% of pupils were using a sunscreen with a sun protection factor (SPF) rating, only 12% had government sponsored tubes of SPF15 cream. Government sponsored sunscreen preparations were only provided if actively sought, involving time consuming trips to regional hospitals, with inadequate availability and insufficient supply.

CONCLUSION

Children with albinism living away from home in rural areas appear to have inadequate sun protection strategies. Changes in health policy could address these deficiencies. We recommend providing more detailed health care information, giving advice on appropriate styles of hat to wear and how to assess commercial SPF products. Health promotional material should also be evaluated to determine its effectiveness among user groups.

Oculocutaneous albinism in a rural community of South Africa: a population genetic study

Oculocutaneous albinism type II (OCA2), the most common form of albinism worldwide, is prevalent throughout sub-Saharan Africa. The hypopigmentory phenotype distinguishes affected individuals as 'different' in a black population, resulting in problems of social acceptance and integration. Health issues include constant, lifelong sun-induced skin damage and poor vision. This study determined the frequency and distribution of albinism among the Vhavenda ethnic group living in the relatively low-income north of South Africa in a clan-oriented society. A retrospective study of birth records from regional hospitals gave an incidence of OCA of 1 in 1970, whereas a survey of mainstream schools gave a frequency of only one pupil with albinism in 13,319 as most affected children attended the regional special school. A community-based field study of 35 rural villages gave a prevalence of 1 in 2239 for OCA. One clan, the Vhatavhatsindi, had a significantly higher frequency of 1 in 832. This epidemiological study provides the necessary data for developing health care and welfare system for families affected by albinism in this region.

Experiences of a feasibility study of children with albinism in Zimbabwe: a discussion paper

BACKGROUND

Feasibility studies are often a helpful prelude to constructing fundable research proposals. Where the intended research is in a foreign country, focuses on a vulnerable population, and is aggravated by political and pragmatic challenges, feasibility studies become essential. Albinism, a genetic condition of reduced melanin synthesis, is a major public health issue in southern Africa. Whilst much is known about the health needs of children with albinism, little is understood about how to address these effectively in low income countries. Further, the child care and protection needs of children with albinism are largely unexplored. Zimbabwe's current political and economic climate presents additional challenges to research on the topic.

METHOD

The technical, economic, legal, collaborative, operational, schedule and political feasibilities (acronym TELCOSP) to undertaking a study on children with albinism in Zimbabwe were explored over a six week period of fieldwork in the country.

RESULTS

Using the TELSCOSP framework allowed a deconstruction of each challenge to provide innovative solutions. The economic and legal feasibility aspects presented some difficulties that will require flexibility and perseverance to overcome.

CONCLUSION

With the assistance of the local communities and people with albinism in Zimbabwe, the obstacles appear surmountable. The feasibility study provided a productive framework for addressing potential challenges in studying the needs of Zimbabwe's children living with albinism.

Scanning transmission X-ray microscopic analysis of purified melanosomes of the mouse iris

Melanosomes are specialized intracellular membrane bound organelles that produce and store melanin pigment. The composition of melanin and distribution of melanosomes determine the color of many mammalian tissues, including the hair, skin, and iris. However, the presence of melanosomes within a tissue carries potentially detrimental risks related to the cytotoxic indole-quinone intermediates produced during melanin synthesis. In order to study melanosomal molecules, including melanin and melanin-related intermediates, we have refined methods allowing spectromicroscopic analysis of purified melanosomes using scanning transmission X-ray microscopy. Here, we present for the first time absorption data for melanosomes at the carbon absorption edge ranging from 284 to 290 eV. High-resolution images of melanosomes at discrete energies demonstrate that fully melanized mature melanosomes are internally non-homogeneous, suggesting the presence of an organized internal sub-structure. Spectra of purified melanosomes are complex, partially described by a predominating absorption band at 288.4 eV with additional contributions from several minor bands. Differences in these spectra were detectable between samples from two strains of inbred mice known to harbor genetically determined melanosomal differences, DBA/2J and C57BL/6J, and are likely to represent signatures arising from biologically relevant and tractable phenomena.

Rapid genetic analysis of oculocutaneous albinism (OCA1) using denaturing high performance liquid chromatography (DHPLC) system

OBJECTIVES

To present the prenatal genetic diagnoses and counseling for two cases of oculocutaneous albinism (OCA) type I family by detection of mutations in the OCA1 gene by denaturing high performance liquid chromatography (DHPLC) system and a review of the literature.

METHODS

All DNA samples were extracted from peripheral whole blood and amniocentesis-derived cells. Mutation analysis was performed for all five coding exons of the TYR gene, which were amplified by PCR. DHPLC was used for heteroduplex detection and sequence analysis was performed to demonstrate the mutation loci.

RESULTS

Case 1: After sampling of blood from the family members and performing amniocentesis of the fetus, it was demonstrated that the affected boy and the female fetus were shown to be compound heterozygotes for mutations in the TYR gene. In addition, it was shown that the parents were carriers of the two mutations. However, the couple chose to keep the baby. Case 2: Mutation analysis of the DNA of the siblings revealed two heterozygous mutations in the TYR gene. Her husband is free of the disease. According to the principles of autosomal recessive inheritance, the incidence of affected offspring is very low.

CONCLUSIONS

Herein we introduce a novel application for molecular diagnostic of DHPLC coupled with direct sequencing, which can provide an effective and exact diagnosis in patients with albinism. Clinicians should be cognizant of the risk of OCA inheritance by the offspring through careful identification of genetic mutations and the inheritance mode, both important to ensure comprehensive genetic counseling.

Ojo y piel

Las relaciones entre la patología del ojo y de su revestimiento cutáneo son muy numerosas. Debido a las analogías embriológicas e histológicas, sus principales consecuencias oftalmológicas afectan a la superficie ocular en el sentido más amplio: tegumentos de los párpados, conjuntivas y córnea. La exploración clínica dermatológica sospechará estas alteraciones, que confirmará el oftalmólogo. No obstante, algunos trastornos pueden afectar a todos los demás tejidos oculares. Ya se trate de una localización ocular de algunas enfermedades dermatológicas, como las dermatosis infecciosas, o de auténticos síndromes oculocutáneos, la exploración clínica especializada, y a veces repetida, suele orientar el tratamiento. Las consecuencias sobre la función visual de algunas de estas alteraciones pueden ser graves. La epidermólisis tóxica de Lyell constituye el ejemplo extremo que puede provocar una ceguera corneal bilateral de tratamiento temible. La dermatitis atópica es otro ejemplo de enfermedad más frecuente, pero cuyas complicaciones oculares también pueden amenazar la visión si el tratamiento oftalmodermatológico no es correcto. El ojo y la piel se asocian de nuevo en numerosas enfermedades generales, congénitas, hereditarias o no, o bien adquiridas, cuyos síntomas específicos relacionados con ambas especialidades ayudan a establecer el diagnóstico positivo. Los ejemplos más frecuentes son el lupus, la enfermedad de Behçet, la sarcoidosis y las facomatosis. La superficie ocular conjuntivocorneal comparte con la piel una cierta similitud en cuanto al desarrollo de tumores, pigmentados o no. Por último, merecen describirse las consecuencias oculares de algunos tratamientos dermatológicos. También se hará mención a las situaciones inversas, que son más excepcionales.