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The British Journal of Ophthalmology Sep 2006Implications for our understanding of the mechanisms of early development of the visual pathway
Implications for our understanding of the mechanisms of early development of the visual pathway
Topics: Albinism, Ocular; Fovea Centralis; Humans; Optic Chiasm; Visual Pathways
PubMed: 16929052
DOI: 10.1136/bjo.2006.097618 -
Genes Jul 2022Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive syndromic form of albinism, characterized by oculocutaneous albinism (OCA) and other systemic...
Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive syndromic form of albinism, characterized by oculocutaneous albinism (OCA) and other systemic complications. The purpose of this study was to investigate patients with HPS-associated gene mutations and describe associated ocular and extraocular phenotypes. Fifty-four probands clinically diagnosed as albinism were enrolled. Ophthalmic examinations and genetic testing were performed in all subjects. The phenotypic and genetic features were evaluated. HPS-associated gene mutation was identified in four of the patients with albinism phenotype. Clinically, photophobia, and nystagmus was detected in all (4/4) patients, and strabismus was found in one (1/4) patient. Fundus examination revealed fundus hypopigmentation and foveal hypoplasia in all (8/8) eyes. Eight novel causative mutations were detected in these four HPS probands. Five (62.5%, 5/8) of the mutations were nonsense, two of the mutations were missense (25%, 2/8), and one of the mutations was frameshift (12.5%, 1/8). All patients in our study carried compound heterozygous variants, and all these pathogenic variants were identified to be novel, with most (62.5%, 5/8) of the mutations being nonsense. Our results improved the understanding of clinical ocular features, and expanded the spectrum of known variants and the genetic background of HPS.
Topics: Eye; Genetic Testing; Hermanski-Pudlak Syndrome; Humans; Mutation; Phenotype
PubMed: 35886065
DOI: 10.3390/genes13071283 -
Indian Journal of Ophthalmology May 2023
Topics: Humans; Albinism, Ocular; Retina; Visual Acuity; Choroid; Tomography, Optical Coherence
PubMed: 37203000
DOI: 10.4103/IJO.IJO_3059_22 -
Investigative Ophthalmology & Visual... Jan 2022The purpose of this study was to further expand the mutational spectrum of the Foveal Hypoplasia, Optic Nerve Decussation defect, and Anterior segment abnormalities... (Comparative Study)
Comparative Study
PURPOSE
The purpose of this study was to further expand the mutational spectrum of the Foveal Hypoplasia, Optic Nerve Decussation defect, and Anterior segment abnormalities (FHONDA syndrome), to describe the phenotypic spectrum, and to compare it to albinism.
SUBJECTS AND METHODS
We retrospectively collected molecular, ophthalmic, and electrophysiological data of 28 patients molecularly confirmed with FHONDA from the Netherlands (9), Israel (13), France (2), and the United States of America (4). We compared the data to that of 133 Dutch patients with the 3 most common types of albinism in the Netherlands: oculocutaneous albinism type 1 (49), type 2 (41), and ocular albinism (43).
RESULTS
Patients with FHONDA had a total of 15 different mutations in SLC38A8, of which 6 were novel. Excluding missing data, all patients had moderate to severe visual impairment (median visual acuity [VA] = 0.7 logMAR, interquartile range [IQR] = 0.6-0.8), nystagmus (28/28), and grade 4 foveal hypoplasia (17/17). Misrouting was present in all nine tested patients. None of the patients had any signs of hypopigmentation of skin and hair. VA in albinism was better (median = 0.5 logMAR, IQR = 0.3-0.7, P 0.006) and the phenotypes were more variable: 14 of 132 without nystagmus, foveal hypoplasia grades 1 to 4, and misrouting absent in 16 of 74.
CONCLUSIONS
Compared to albinism, the FHONDA syndrome appears to have a more narrow phenotypic spectrum, consisting of nonprogressive moderately to severely reduced VA, nystagmus, severe foveal hypoplasia, and misrouting. The co-occurrence of nystagmus, foveal hypoplasia, and misrouting in the absence of hypopigmentation implies that these abnormalities are not caused by lack of melanin, which has important implications for understanding the pathogenesis of these features.
Topics: Adolescent; Adult; Aged; Albinism, Oculocutaneous; Amino Acid Transport Systems, Neutral; Anterior Eye Segment; Child; Child, Preschool; DNA; DNA Mutational Analysis; Female; Follow-Up Studies; Fovea Centralis; Humans; Infant; Male; Middle Aged; Mutation; Phenotype; Retrospective Studies; Syndrome; Visual Acuity; Young Adult
PubMed: 35029636
DOI: 10.1167/iovs.63.1.19 -
Human Brain Mapping Feb 2017Albinism is a group of congenital disorders of the melanin synthesis pathway. Multiple ocular, white matter and cortical abnormalities occur in albinism, including a...
Albinism is a group of congenital disorders of the melanin synthesis pathway. Multiple ocular, white matter and cortical abnormalities occur in albinism, including a greater decussation of nerve fibres at the optic chiasm, foveal hypoplasia and nystagmus. Despite this, visual perception is largely preserved. It was proposed that this may be attributable to reorganisation among cerebral networks, including an increased interhemispheric connectivity of the primary visual areas. A graph-theoretic model was applied to explore brain connectivity networks derived from resting-state functional and diffusion-tensor magnetic resonance imaging data in 23 people with albinism and 20 controls. They tested for group differences in connectivity between primary visual areas and in summary network organisation descriptors. Main findings were supplemented with analyses of control regions, brain volumes and white matter microstructure. Significant functional interhemispheric hyperconnectivity of the primary visual areas in the albinism group were found (P = 0.012). Tests of interhemispheric connectivity based on the diffusion-tensor data showed no significant group difference (P = 0.713). Second, it was found that a range of functional whole-brain network metrics were abnormal in people with albinism, including the clustering coefficient (P = 0.005), although this may have been driven partly by overall differences in connectivity, rather than reorganisation. Based on the results, it was suggested that changes occur in albinism at the whole-brain level, and not just within the visual processing pathways. It was proposed that their findings may reflect compensatory adaptations to increased chiasmic decussation, foveal hypoplasia and nystagmus. Hum Brain Mapp 38:740-752, 2017. © 2016 Wiley Periodicals, Inc.
Topics: Adolescent; Adult; Albinism; Brain; Brain Mapping; Diffusion Magnetic Resonance Imaging; Female; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Male; Middle Aged; Nerve Fibers, Myelinated; Neural Pathways; Oxygen; Severity of Illness Index; Young Adult
PubMed: 27684406
DOI: 10.1002/hbm.23414 -
Oxford Medical Case Reports Feb 2023Hermansky-Pudlak syndrome (HPS) is a rare multisystem disorder inherited in an autosomal recessive manner. Its prevalence is 1 in 500 000 to 1 000 000 people...
Hermansky-Pudlak syndrome (HPS) is a rare multisystem disorder inherited in an autosomal recessive manner. Its prevalence is 1 in 500 000 to 1 000 000 people worldwide. The cause of this disorder is genetic mutations that lead to defective organelles of lysosomes. In this report, a 49-year-old man is introduced who was referred to the medical center with ocular albinism and recently exacerbated shortness of breath. Imaging showed peripheral reticular opacities, ground-glass opacities of the lungs with subpleural sparing in some regions, and thickening of bronchovascular bundles, which were all in favor of non-specific interstitial pneumonia. This imaging pattern is an unusual finding in a patient with HPS.
PubMed: 36860960
DOI: 10.1093/omcr/omad001 -
The American Journal of Case Reports Sep 2020BACKGROUND Retinal vasoproliferative tumor (VPT) is a type of ocular vascular tumor that commonly occurs idiopathically and can be associated with secondary ocular...
BACKGROUND Retinal vasoproliferative tumor (VPT) is a type of ocular vascular tumor that commonly occurs idiopathically and can be associated with secondary ocular diseases. Ocular albinism is an X-linked inherited disease and distinguished from oculocutaneous albinism by less hair and skin involvement. CASE REPORT A 42-year-old man with ocular albinism and moderate myopia presented with a history of insidious decrease in vision in both eyes over a period of months. On examination, the horizontal pendular nystagmus was present and diffuse iris transillumination defects were observed bilaterally. A fundus examination revealed a depigmented fundus with visible choroidal vessels, foveal hypoplasia, and a unilateral, elevated, vascular lesion in the superotemporal aspect of the retinal periphery. Optical coherence tomography of the lesion confirmed the retinal location and fluorescein fundus angiography indicated its vascular nature. B-scan ultrasonography was performed to measure the dimensions of the lesion. CONCLUSIONS Rare retinal VPT has been reported with systemic and ocular associations, but it has never been reported in the literature in association with ocular albinism. Multiple treatment modalities have been described for the tumor, but observation can be considered in the absence of secondary consequences of the VPT. Retinal VPT should be included in the differential diagnosis of any retinal vascular abnormalities in patients with ocular albinism.
Topics: Adult; Albinism, Ocular; Albinism, Oculocutaneous; Fluorescein Angiography; Fundus Oculi; Humans; Male; Tomography, Optical Coherence
PubMed: 32895362
DOI: 10.12659/AJCR.925926 -
Integrative and Comparative Biology Oct 2021Melanins, the main pigments of the skin and hair in mammals, are synthesized within membrane-bound organelles of melanocytes called melanosomes. Melanosome structure and... (Review)
Review
Melanins, the main pigments of the skin and hair in mammals, are synthesized within membrane-bound organelles of melanocytes called melanosomes. Melanosome structure and function are determined by a cohort of resident transmembrane proteins, many of which are expressed only in pigment cells and localize specifically to melanosomes. Defects in the genes that encode melanosome-specific proteins or components of the machinery required for their transport in and out of melanosomes underlie various forms of ocular or oculocutaneous albinism, characterized by hypopigmentation of the hair, skin, and eyes and by visual impairment. We review major components of melanosomes, including the enzymes that catalyze steps in melanin synthesis from tyrosine precursors, solute transporters that allow these enzymes to function, and structural proteins that underlie melanosome shape and melanin deposition. We then review the molecular mechanisms by which these components are biosynthetically delivered to newly forming melanosomes-many of which are shared by other cell types that generate cell type-specific lysosome-related organelles. We also highlight unanswered questions that need to be addressed by future investigation.
Topics: Animals; Mammals; Melanins; Melanocytes; Melanosomes; Pigmentation
PubMed: 34021746
DOI: 10.1093/icb/icab078 -
Frontiers in Molecular Biosciences 2022GPCRs transform extracellular stimuli into a physiological response by activating an intracellular signaling cascade initiated via binding to G proteins. Orphan G... (Review)
Review
GPCRs transform extracellular stimuli into a physiological response by activating an intracellular signaling cascade initiated via binding to G proteins. Orphan G protein-coupled receptors (GPCRs) hold the potential to pave the way for development of new, innovative therapeutic strategies. In this review we will introduce G protein-coupled receptor 143 (GPR143), an enigmatic receptor in terms of classification within the GPCR superfamily and localization. GPR143 has not been assigned to any of the GPCR families due to the lack of common structural motifs. Hence we will describe the most important motifs of classes A and B and compare them to the protein sequence of GPR143. While a precise function for the receptor has yet to be determined, the protein is expressed abundantly in pigment producing cells. Many GPR143 mutations cause X-linked Ocular Albinism Type 1 (OA1, Nettleship-Falls OA), which results in hypopigmentation of the eyes and loss of visual acuity due to disrupted visual system development and function. In pigment cells of the skin, loss of functional GPR143 results in abnormally large melanosomes (organelles in which pigment is produced). Studies have shown that the receptor is localized internally, including at the melanosomal membrane, where it may function to regulate melanosome size and/or facilitate protein trafficking to the melanosome through the endolysosomal system. Numerous additional roles have been proposed for GPR143 in determining cancer predisposition, regulation of blood pressure, development of macular degeneration and signaling in the brain, which we will briefly describe as well as potential ligands that have been identified. Furthermore, GPR143 is a promiscuous receptor that has been shown to interact with multiple other melanosomal proteins and GPCRs, which strongly suggests that this orphan receptor is likely involved in many different physiological actions.
PubMed: 35495622
DOI: 10.3389/fmolb.2022.873777