Frequency, Genotype, and Clinical Spectrum of Best Vitelliform Macular Dystrophy: Data From a National Center in Denmark

PURPOSE: To estimate the prevalence, genotype, and clinical spectrum of Best vitelliform macular dystrophy (Best disease). DESIGN: Retrospective epidemiologic and clinical and molecular genetic observational study. METHODS: SETTING: National referral center. PARTICIPANTS: Forty-five individuals diagnosed with Best disease. OBSERVATION PROCEDURES: Retrospective review of patients diagnosed according to clinical findings and sequencing of BEST1. Patients with recently established molecular genetic diagnosis were followed up including multifocal electroretinography (mfERG), spectral-domain optical coherence tomography (SD-OCT), and fundus autofluorescence (FAF) imaging. MAIN OUTCOME MEASURES: BEST1 mutations, SD-OCT and FAF findings, mfERG amplitudes, prevalence estimate of Best disease. RESULTS: BEST1 mutations described previously in Danish patients with Best disease are reviewed. In addition, we identified a further 8 families and 1 sporadic case, in whom 6 BEST1 missense mutations were found, 4 of which are novel. The mutation c.904G>T (p.Asp302Asn) was identified in members of 4 unrelated families. Structural alterations ranged from precipitate-like alterations at the level of the photoreceptor outer segments (OS) to choroidal neovascularization. The extent of the former correlated with the reduction of retinal function. A prevalence estimate of Best disease in Denmark based on the number of diagnosed cases was 1.5 per 100 000 individuals. CONCLUSIONS: Our data expand the mutation spectrum of BEST1 in patients with Best disease. Alterations of the OS overlying lesions with subretinal fluid are similar to those seen in central serous retinopathy and may indicate impaired turnover of OS. Our frequency estimate confirms that Best disease is one of the most common causes of early macular degeneration. (Am J Ophthalmol 2012;154:403-412. (c) 2012 by Elsevier Inc. All rights reserved.

Homozygosity for a novel ABCA4 founder splicing mutation is associated with progressive and severe Stargardt-like disease

PURPOSE. To clinically characterize and genetically analyze members of six families who reside in the same village and manifest a rare form of retinal degeneration. METHODS. Ophthalmic evaluation included a full clinical examination, perimetry, color vision testing, and electroretinography. Genomic DNA was screened for ABCA4 mutations with the use of microarray analysis and direct sequencing. RNA analysis was performed with RT-PCR and sequencing. RESULTS. The authors recruited 15 patients with a unique retinal disease who are members of six highly consanguineous ArabMuslim families from a single village. During early stages of disease, funduscopic and angiographic findings as well as retinal function resemble those of Stargardt disease. However, later in life, severe, widespread cone-rod degeneration ensues. Marked progressive involvement of the retinal periphery distinguishes this phenotype from classic Stargardt disease. Genetic analysis of ABCA4 revealed two novel deletions, p.Cys1150del and c.4254-15del23. One patient, who was a compound heterozygote, manifested typical Stargardt disease. The remaining 14 patients were homozygote for the c.4254-15del23 intronic deletion and had the progressive form of disease. We identified an identical ABCA4 haplotype in all alleles carrying this mutation, indicating a founder mutation. Detailed RT-PCR analysis in normal retina and lymphoblastoid cells revealed expression of the full-length ABCA4 transcript and three novel transcripts produced by alternative splicing. The full-length ABCA4 transcript, however, could not be detected in lymphoblastoid cells of affected homozygote patients. CONCLUSIONS. These results expand the genotype-phenotype correlation of ABCA4, showing that homozygosity for the novel c.4254-15del23 splicing mutation is associated with a severe progressive form of disease. (Invest Ophthalmol Vis Sci

The Effect of Cone Opsin Mutations on Retinal Structure and the Integrity of the Photoreceptor Mosaic

Purpose. To evaluate retinal structure and photoreceptor mosaic integrity in subjects with OPN1LW and OPN1MW mutations. Methods. Eleven subjects were recruited, eight of whom have been previously described. Cone and rod density was measured using images of the photoreceptor mosaic obtained from an adaptive optics scanning light ophthalmoscope (AOSLO). Total retinal thickness, inner retinal thickness, and outer nuclear layer plus Henle fiber layer (ONL+HFL) thickness were measured using cross-sectional spectral-domain optical coherence tomography (SD-OCT) images. Molecular genetic analyses were performed to characterize the OPN1LW/OPN1MW gene array. Results. While disruptions in retinal lamination and cone mosaic structure were observed in all subjects, genotype-specific differences were also observed. For example, subjects with “L/M interchange” mutations resulting from intermixing of ancestral OPN1LW and OPN1MW genes had significant residual cone structure in the parafovea (∼25% of normal), despite widespread retinal disruption that included a large foveal lesion and thinning of the parafoveal inner retina. These subjects also reported a later-onset, progressive loss of visual function. In contrast, subjects with the C203R missense mutation presented with congenital blue cone monochromacy, with retinal lamination defects being restricted to the ONL+HFL and the degree of residual cone structure (8% of normal) being consistent with that expected for the S-cone submosaic. Conclusions. The photoreceptor phenotype associated with OPN1LW and OPN1MW mutations is highly variable. These findings have implications for the potential restoration of visual function in subjects with opsin mutations. Our study highlights the importance of high-resolution phenotyping to characterize cellular structure in inherited retinal disease; such information will be critical for selecting patients most likely to respond to therapeutic intervention and for establishing a baseline for evaluating treatment efficacy

A tapetal-like fundus reflex in a healthy male: evidence against a role in the pathophysiology of retinal degeneration?

Purpose: To report on the retinal function and structure in a 37-year-old male who presented with a tapetal-like reflex (TLR) indistinguishable from that seen in female carriers of X-linked retinitis pigmentosa (XLRP). Methods: Clinical examination included dark adaptometry, full-field electroretinography (ERG), multifocal ERG, optical coherence tomography, and fundus autofluorescence photography. Molecular genetic testing included screening for known mutations in autosomal dominant, autosomal recessive, and X linked retinitis pigmentosa (RP) genes with a commercially available chip, and sequencing analysis of retinitis pigmentosa GTPase regulator (RPGR)-open reading frame 15 (ORF15). Results: Fundus examination revealed a bilateral TLR, which is typical of female carriers of XLRP. Imaging studies and electrophysiological testing was unremarkable, except for a significant increase in full-field ERG amplitudes after prolonged dark adaptation as compared to after standard dark adaptation. Mutation screening was negative. Conclusions: TLR was found for the first time, to the best of our knowledge, in a male subject. There were no definitive signs of retinal degeneration, suggesting that this reflex in itself is not necessarily a precursor of the retinal degeneration that can be seen in female carriers of XLRP

A tapetal-like fundus reflex in a healthy male:evidence against a role in the pathophysiology of retinal degeneration?

Purpose: To report on the retinal function and structure in a 37-year-old male who presented with a tapetal-like reflex (TLR) indistinguishable from that seen in female carriers of X-linked retinitis pigmentosa (XLRP). Methods: Clinical examination included dark adaptometry, full-field electroretinography (ERG), multifocal ERG, optical coherence tomography, and fundus autofluorescence photography. Molecular genetic testing included screening for known mutations in autosomal dominant, autosomal recessive, and X linked retinitis pigmentosa (RP) genes with a commercially available chip, and sequencing analysis of retinitis pigmentosa GTPase regulator (RPGR)-open reading frame 15 (ORF15). Results: Fundus examination revealed a bilateral TLR, which is typical of female carriers of XLRP. Imaging studies and electrophysiological testing was unremarkable, except for a significant increase in full-field ERG amplitudes after prolonged dark adaptation as compared to after standard dark adaptation. Mutation screening was negative. Conclusions: TLR was found for the first time, to the best of our knowledge, in a male subject. There were no definitive signs of retinal degeneration, suggesting that this reflex in itself is not necessarily a precursor of the retinal degeneration that can be seen in female carriers of XLRP

Ocular Phenotype Analysis of a Family With Biallelic Mutations in the BEST1 Gene

To investigate the genetic cause and perform a comprehensive clinical analysis of a Danish family with autosomal recessive bestrophinopathy. To investigate whether Bestrophin may be expressed in normal human retina

Knockdown of dehydrodolichyl diphosphate synthase in the drosophila retina leads to a unique pattern of retinal degeneration

Dehydrodolichyl diphosphate synthase (DHDDS) is a ubiquitously expressed enzyme that catalyzes cis-prenyl chain elongation to produce the poly-prenyl backbone of dolichol. It appears in all tissues including the nervous system and it is a highly conserved enzyme that can be found in all animal species. Individuals who have biallelic missense mutations in the DHDDS gene are presented with non-syndromic retinitis pigmentosa with unknown underlying mechanism. We have used the Drosophila model to compromise DHDDS ortholog gene (CG10778) in order to look for cellular and molecular mechanisms that, when defective, might be responsible for this retinal disease. The Gal4/UAS system was used to suppress the expression of CG10778 via RNAi-mediated-knockdown in various tissues. The resulting phenotypes were assessed using q-RT-PCR, transmission-electron-microscopy (TEM), electroretinogram, antibody staining and Western blot analysis. Targeted knockdown of CG10778-mRNA in the early embryo using the actin promoter or in the developing wings using the nub promoter resulted in lethality, or wings loss, respectively. Targeted expression of CG10778-RNAi using the glass multiple reporter (GMR)-Gal4 driver (GMR-DHDDS-RNAi) in the larva eye disc and pupal retina resulted in a complex phenotype: (a) TEM retinal sections revealed a unique pattern of retinal-degeneration, where photoreceptors R2 and R5 exhibited a nearly normal structure of their signaling-compartment (rhabdomere), but only at the region of the nucleus, while all other photoreceptors showed retinal degeneration at all regions. (b) Western blot analysis revealed a drastic reduction in rhodopsin levels in GMR-DHDDS-RNAi-flies and TEM sections showed an abnormal accumulation of endoplasmic reticulum (ER). To conclude, compromising DHDDS in the developing retina, while allowing formation of the retina, resulted in a unique pattern of retinal degeneration, characterized by a dramatic reduction in rhodopsin protein level and an abnormal accumulation of ER membranes in the photoreceptors cells, thus indicating that DHDDS is essential for normal retinal formation

The Effect of Cone Opsin Mutations on Retinal Structure and the Integrity of the Photoreceptor MosaicEffect of Opsin Mutations on Photoreceptor Phenotype

PurposeTo evaluate retinal structure and photoreceptor mosaic integrity in subjects with OPN1LW and OPN1MW mutations.MethodsEleven subjects were recruited, eight of whom have been previously described. Cone and rod density was measured using images of the photoreceptor mosaic obtained from an adaptive optics scanning light ophthalmoscope (AOSLO). Total retinal thickness, inner retinal thickness, and outer nuclear layer plus Henle fiber layer (ONL+HFL) thickness were measured using cross-sectional spectral-domain optical coherence tomography (SD-OCT) images. Molecular genetic analyses were performed to characterize the OPN1LW/OPN1MW gene array.ResultsWhile disruptions in retinal lamination and cone mosaic structure were observed in all subjects, genotype-specific differences were also observed. For example, subjects with "L/M interchange" mutations resulting from intermixing of ancestral OPN1LW and OPN1MW genes had significant residual cone structure in the parafovea (∼25% of normal), despite widespread retinal disruption that included a large foveal lesion and thinning of the parafoveal inner retina. These subjects also reported a later-onset, progressive loss of visual function. In contrast, subjects with the C203R missense mutation presented with congenital blue cone monochromacy, with retinal lamination defects being restricted to the ONL+HFL and the degree of residual cone structure (8% of normal) being consistent with that expected for the S-cone submosaic.ConclusionsThe photoreceptor phenotype associated with OPN1LW and OPN1MW mutations is highly variable. These findings have implications for the potential restoration of visual function in subjects with opsin mutations. Our study highlights the importance of high-resolution phenotyping to characterize cellular structure in inherited retinal disease; such information will be critical for selecting patients most likely to respond to therapeutic intervention and for establishing a baseline for evaluating treatment efficacy

Homozygosity Mapping Reveals Null Mutations in FAM161A as a Cause of Autosomal-Recessive Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal degenerations caused by mutations in at least 45 genes. Using homozygosity mapping, we identified a ∼4 Mb homozygous region on chromosome 2p15 in patients with autosomal-recessive RP (arRP). This region partially overlaps with RP28, a previously identified arRP locus. Sequence analysis of 12 candidate genes revealed three null mutations in FAM161A in 20 families. RT-PCR analysis in 21 human tissues revealed high levels of FAM161A expression in the retina and lower levels in the brain and testis. In the human retina, we identified two alternatively spliced transcripts with an intact open reading frame, the major one lacking a highly conserved exon. During mouse embryonic development, low levels of Fam161a transcripts were detected throughout the optic cup. After birth, Fam161a expression was elevated and confined to the photoreceptor layer. FAM161A encodes a protein of unknown function that is moderately conserved in mammals. Clinical manifestations of patients with FAM161A mutations varied but were largely within the spectrum associated with arRP. On funduscopy, pallor of the optic discs and attenuation of blood vessels were common, but bone-spicule-like pigmentation was often mild or lacking. Most patients had nonrecordable electroretinographic responses and constriction of visual fields upon diagnosis. Our data suggest a pivotal role for FAM161A in photoreceptors and reveal that FAM161A loss-of-function mutations are a major cause of arRP, accounting for ∼12% of arRP families in our cohort of patients from Israel and the Palestinian territories