A novel mutation in the ABCR gene in four patients with autosomal recessive Stargardt disease

PURPOSE: To identify additional mutations in the ABCR gene and describe the clinical features of four affected siblings with autosomal recessive Stargardt disease. METHODS: A cohort of eight siblings was identified for study. Four of these individuals were diagnosed with Stargardt disease based on clinical evaluation and fluorescein angiography. Blood samples were obtained from seven of eight siblings, including all those affected. All 50 exons of the ABCR gene were analyzed by single-stranded confirmation polymorphism analysis, followed by direct sequencing of observed variants, to identify mutations in the ABCR gene. RESULTS: We identified a previously unreported kindred of eight siblings, four of whom had mutations in both of their ABCR alleles. A previously described G-to-C transversion of nucleotide 2588, predicting a Gly863Ala amino acid substitution, and a novel G-to-A transition of nucleotide 161, resulting in a Cys54Tyr substitution, were identified. These mutations co-segregated with the affected members of this family. Three of the siblings demonstrated clinical features characteristic of classic Stargardt disease, with bilateral regions of macular atrophy associated with yellow-white “flavimaculatus” flecks in the posterior pole at the level of the retinal pigment epithelium. The fourth affected sibling showed features of early Stargardt disease, with a beaten-bronze appearance to both maculas, as well as perimacular flecks. In all four affected patients, fluorescein angiography showed a characteristic peripheral dark choroid. CONCLUSIONS: We have identified both a previously described and a novel mutation in the ABCR gene in four patients with autosomal recessive Stargardt disease. In-depth knowledge of the ABCR mutation spectrum in patients with Stargardt disease will provide for more efficient screening and may provide potential therapies for Stargardt disease and other retinal diseases

Clinicopathologic Findings in Three Siblings With Geographic Atrophy

Age-related macular degeneration (AMD) is a leading cause of blindness among the elderly worldwide. Clinical imaging and histopathologic studies are crucial to understanding disease pathology. This study combined clinical observations of three brothers with geographic atrophy (GA), followed for 20 years, with histopathologic analysis. For two of the three brothers, clinical images were taken in 2016, 2 years prior to death. Immunohistochemistry, on both flat-mounts and cross sections, histology, and transmission electron microscopy were used to compare the choroid and retina in GA eyes to those of age-matched controls. Ulex europaeus agglutinin (UEA) lectin staining of the choroid demonstrated a significant reduction in the percent vascular area and vessel diameter. In one donor, histopathologic analysis demonstrated two separate areas with choroidal neovascularization (CNV). Reevaluation of swept-source optical coherence tomography angiography (SS-OCTA) images revealed CNV in two of the brothers. UEA lectin also revealed a significant reduction in retinal vasculature in the atrophic area. A subretinal glial membrane, composed of processes positive for glial fibrillary acidic protein and/or vimentin, occupied areas identical to those of retinal pigment epithelium (RPE) and choroidal atrophy in all three AMD donors. SS-OCTA also demonstrated presumed calcific drusen in the two donors imaged in 2016. Immunohistochemical analysis and alizarin red S staining verified calcium within drusen, which was ensheathed by glial processes. This study demonstrates the importance of clinicohistopathologic correlation studies. It emphasizes the need to better understand how the symbiotic relationship between choriocapillaris and RPE, glial response, and calcified drusen impact GA progression

Electroretinographic abnormalities in parents of patients with Leber Congenital Amaurosis who have Heterozygous GUCY2D mutations

Background Leber congenital amaurosis (LCA) is an infrequently encountered congenital form of retinitis pigmentosa with marked genetic and clinical heterogeneity. Thus far, 10 genes have been identified in this disorder since 1996. In the future, LCA may become treatable by gene and/or pharmacological intervention, and these therapies will likely be gene specific, giving major significance to rapid gene identification and gene-phenotype studies. Objective To test the hypothesis that parents of patients with LCA have identifiable electroretinographic and psychophysical changes. Subjects, Materials, and Methods Complete eye examinations and electroretinographic studies were performed on 2 sets of parents whose offspring were diagnosed as having LCA and who were found to carry a mutation in 1 of the 10 LCA genes—GUCY2D. One set of parents also underwent static perimetry threshold measurements. Results We found that single flash-light–adapted a- and b-wave amplitudes, 30-Hz flicker, or both cone signals were significantly decreased in amplitude in 4 heterozygotes, while 2 parents showed delayed 30-Hz flicker implicit times. Electroretinographic rod-mediated signals were normal in 2 of the heterozygotes, but subnormal in 2. Static perimetry testing showed normal thresholds in the 2 heterozygotes tested. Main Outcome Measures Single flash-light–adapted a- and b-wave amplitudes and implicit times, 30- or 32-Hz flicker amplitudes and implicit times, rod-mediated signals, and dark-adapted, rod-mediated thresholds. Conclusions Some carrier parents of patients with LCA and a GUCY2D mutation develop measurable, cone and possibly rod abnormalities most consistent with a mild cone-rod dysfunction. This correlates well with the known retinal expression pattern of GUCY2D, which is considerably higher in cone compared with rod photoreceptor cells. <br/

Extreme hyperopia is the result of null mutations in MFRP, which encodes a Frizzled-related protein

Nanophthalmos is a rare disorder of eye development characterized by extreme hyperopia (farsightedness), with refractive error in the range of +8.00 to +25.00 diopters. Because the cornea and lens are normal in size and shape, hyperopia occurs because insufficient growth along the visual axis places these lensing components too close to the retina. Nanophthalmic eyes show considerable thickening of both the choroidal vascular bed and scleral coat, which provide nutritive and structural support for the retina. Thickening of these tissues is a general feature of axial hyperopia, whereas the opposite occurs in myopia. We have mapped recessive nanophthalmos to a unique locus at 11q23.3 and identified four independent mutations in MFRP, a gene that is selectively expressed in the eye and encodes a protein with homology to Tolloid proteases and the Wnt-binding domain of the Frizzled transmembrane receptors. This gene is not critical for retinal function, as patients entirely lacking MFRP can still have good refraction-corrected vision, produce clinically normal electro-retinograms, and show only modest anomalies in the dark adaptation of photoreceptors. MFRP appears primarily devoted to regulating axial length of the eye. It remains to be determined whether natural variation in its activity plays a role in common refractive errors