Sharon B Schwartz

William Penn University, Filadelfia, Pennsylvania, United States

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Publications (65)397.57 Total impact

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    ABSTRACT: Leber congenital amaurosis (LCA) patients of 10 known genotypes (n = 24; age range, 3–25 years) were studied clinically and by optical coherence tomography (OCT). Comparisons were made between OCT results across the horizontal meridian (central 60o) of the patients. Three patterns were identified. First, there were LCA genotypes with unusual and readily identifiable patterns, such as near normal outer nuclear layer (ONL) across the central retina or severely dysplastic retina. Second, there were genotypes with well-formed foveal architecture but only residual central islands of normal or reduced ONL thickness. Third, some genotypes showed central ONL losses or dysmorphology suggesting early macular disease or foveal maldevelopment. Objective in vivo morphological features could complement other phenotypic characteristics and help guide genetic testing of LCA patients or at least permit a differential diagnosis of genotypes to be made in the clinic.
    No preview · Article · Oct 2016 · Advances in Experimental Medicine and Biology
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    ABSTRACT: Purpose: To characterize in detail the phenotype and genotype of patients with pericentral retinal degeneration (PRD). Methods: Patients were screened for an annular ring scotoma ranging from 3° to 40° (n = 28, ages 24-71) with kinetic perimetry. All patients had pigmentary retinopathy in the region of the dysfunction. Further studies included cross-sectional and en face imaging, static chromatic perimetry, and electroretinography. Molecular screening was performed. Results: Genotypes of 14 of 28 PRD patients were identified: There were mutations in eight different genes previously associated with autosomal dominant or autosomal recessive RDs. Kinetic fields monitored in some patients over years to more than a decade could be stable or show increased extent of the scotoma. Electroretinograms were recordable but with different severities of dysfunction. Patterns of photoreceptor outer nuclear layer (ONL) loss corresponded to the distribution of visual dysfunction. Outer nuclear layer thickness topography and en face imaging indicated that the greatest disease expression was in the area of known highest rod photoreceptor density. Conclusions: Molecular heterogeneity was a feature of the PRD phenotype. Many of the molecular causes were also associated with other phenotypes, such as maculopathies, typical retinitis pigmentosa (RP) and cone-rod dystrophy. The pericentral pattern of retinal degeneration is thus confirmed to be an uncommon phenotype of many different genotypes rather than a distinct disease entity.
    No preview · Article · Sep 2015 · Investigative ophthalmology & visual science
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    ABSTRACT: Purpose: To evaluate the progression of the earliest stage of disease in ABCA4-associated retinal degenerations (RDs). Methods: Near-infrared excited reduced-illuminance autofluorescence imaging was acquired across the retina up to 80 degrees eccentricity in 44 patients with two ABCA4 alleles. The eccentricity of the leading disease front (LDF) corresponding to the earliest stage of disease was measured along the four meridians. A mathematical model describing the expansion of the LDF was developed based on 6 years of longitudinal follow-up. Results: The extent of LDF along the superior, inferior, and temporal meridians showed a wide spectrum from 3.5 to 70 degrees. In patients with longitudinal data, the average centrifugal expansion rate was 2 degrees per year. The nasal extent of LDF between the fovea and ONH ranged from 4.3 to 16.5 degrees and expanded at 0.35 degrees per year. The extent of LDF beyond ONH ranged from 19 to 75 degrees and expanded on average at 2 degrees per year. A mathematical model fit well to the longitudinal data describing the expansion of the LDF. Conclusions: The eccentricity of the LDF in ABCA4-RD shows a continuum from parafovea to far periphery along all four meridians consistent with a wide spectrum of severity observed clinically. The model of progression may provide a quantitative prediction of the LDF expansion based on the age and eccentricity of the LDF at a baseline visit, and thus contribute significantly to the enrollment of candidates appropriate for clinical trials planning specific interventions, efficacy outcomes, and durations.
    Full-text · Article · Sep 2015 · Investigative ophthalmology & visual science
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    ABSTRACT: Background: Inherited retinal degenerations (IRDs) preferentially affecting cone photoreceptor function are being considered for treatment trials aiming to improve day vision. The purpose of the current work was to develop cone-specific visual orientation outcomes that can differentiate day vision improvement in the presence of retained night vision. Methods: A lighted wall (1.4 m wide, 2 m high) resembling a beaded curtain was formed with 900 individually addressable red, blue and green LED triplets placed in 15 vertical strips hanging 0.1 m apart. Under computer control, different combination of colors and intensities were used to produce the appearance of a door on the wall. Scotopically-matched trials were designed to be perceptible to the cone-, but not rod-, photoreceptor based visual systems. Unmatched control trials were interleaved at each luminance level to determine the existence of any vision available for orientation. Testing started with dark-adapted eyes and a scene luminance attenuated 8 log units from the maximum attainable, and continued with progressively increasing levels of luminance. Testing was performed with a three-alternative forced choice method in healthy subjects and patients with Leber congenital amaurosis (LCA) caused by mutations in GUCY2D, the gene that encodes retinal guanylate cyclase-1. Results: Normal subjects could perform the orientation task using cone vision at 5 log attenuation and brighter luminance levels. Most GUCY2D-LCA patients failed to perform the orientation task with scotopically-matched test trials at any luminance level even though they were able to perform correctly with unmatched control trials. These results were consistent with a lack of cone system vision and use of the rod system under ambient conditions normally associated with cone system activity. Two GUCY2D-LCA patients demonstrated remnant cone vision but at a luminance level 2 log brighter than normal. Conclusions: The newly developed device can probe the existence or emergence of cone-based vision in patients for an orientation task involving the identification of a door on the wall under free-viewing conditions. This key advance represents progress toward developing an appropriate outcome measure for a clinical trial to treat currently incurable eye diseases severely affecting cone vision despite retained rod vision.
    Full-text · Article · Aug 2015 · BMC Ophthalmology
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    ABSTRACT: Retinal gene therapy for Leber’s congenital amaurosis, an autosomal recessive childhood blindness, has been widely considered to be safe and efficacious. Three years after therapy, improvement in vision was maintained, but the rate of loss of photoreceptors in the treated retina was the same as that in the untreated retina. Here we describe long-term follow-up data from three treated patients. Topographic maps of visual sensitivity in treated regions, nearly 6 years after therapy for two of the patients and 4.5 years after therapy for the third patient, indicate progressive diminution of the areas of improved vision.
    No preview · Article · May 2015 · New England Journal of Medicine
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    ABSTRACT: Background: Blue Cone Monochromacy (BCM) is an X-linked retinopathy caused by mutations in the OPN1LW / OPN1MW gene cluster, encoding long (L)- and middle (M)-wavelength sensitive cone opsins. Recent evidence shows sufficient structural integrity of cone photoreceptors in BCM to warrant consideration of a gene therapy approach to the disease. In the present study, the vision in BCM is examined, specifically seeking clinically-feasible outcomes for a future clinical trial. Methods: BCM patients (n = 25, ages 5-72) were studied with kinetic and static chromatic perimetry, full-field sensitivity testing, and eye movement recordings. Vision at the fovea and parafovea was probed with chromatic microperimetry. Results: Kinetic fields with a Goldmann size V target were generally full. Short-wavelength (S-) sensitive cone function was normal or near normal in most patients. Light-adapted perimetry results on conventional background lights were abnormally reduced; 600-nm stimuli were seen by rods whereas white stimuli were seen by both rods and S-cones. Under dark-adapted conditions, 500-nm stimuli were seen by rods in both BCM and normals. Spectral sensitivity functions in the superior retina showed retained rod and S-cone functions in BCM under dark-adapted and light-adapted conditions. In the fovea, normal subjects showed L/M-cone mediation using a 650-nm stimulus under dark-adapted conditions, whereas BCM patients had reduced sensitivity driven by rod vision. Full-field red stimuli on bright blue backgrounds were seen by L/M-cones in normal subjects whereas BCM patients had abnormally reduced and rod-mediated sensitivities. Fixation location could vary from fovea to parafovea. Chromatic microperimetry demonstrated a large loss of sensitivity to red stimuli presented on a cyan adapting background at the anatomical fovea and surrounding parafovea. Conclusions: BCM rods continue to signal vision under conditions normally associated with daylight vision. Localized and retina-wide outcome measures were examined to evaluate possible improvement of L/M-cone-based vision in a clinical trial.
    Full-text · Article · Apr 2015 · PLoS ONE
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    ABSTRACT: Mutations in the ABCA4 gene are a common cause of autosomal recessive retinal degeneration. All mouse models to date are based on knockouts of Abca4, even though the disease is often caused by missense mutations such as the complex allele L541P;A1038V (PV). We now show that the PV mutation causes severe human disease whereas the V mutation alone causes mild disease. Mutant ABCA4 proteins expressed heterologously in mammalian cells retained normal cellular localization. However, basal and all-trans-retinal-stimulated ATPase activities were reduced substantially for P and PV but only mildly for V. Electron microscopy revealed marked structural changes and misfolding for the P and PV mutants but few changes for the V mutant, consistent with the disease severity difference in patients. We generated Abca4(PV/PV) knock-in mice homozygous for the complex PV allele to investigate the effects of this misfolding mutation in vivo. Mutant ABCA4 RNA approximated WT ABCA4 RNA levels but, surprisingly, only trace amounts of mutant ABCA4 protein were noted in the retina. RNA sequencing of WT, Abca4(-/-) and Abca4(PV/PV) mice revealed gene expression alterations in the retina and RPE. Similar to Abca4(-/-) mice, Abca4(PV/PV) mice showed substantial A2E and lipofuscin accumulation in their RPE cells but no retinal degeneration up to 12 months of age. Thus, rapid degradation of this large misfolded mutant protein in mouse retina caused little detectable photoreceptor degeneration. These findings suggest likely differences in the unfolded protein response between murine and human photoreceptors, and clinical treatments directed at increasing this capability. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
    Full-text · Article · Feb 2015 · Human Molecular Genetics
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    ABSTRACT: Achromatopsia (ACHM) is a congenital, autosomal recessive retinal disease that manifests cone dysfunction, reduced visual acuity and color vision, nystagmus, and photoaversion. Five genes are known causes of ACHM. The present study took steps toward performing a trial of gene therapy in ACHM by characterizing the genetics of ACHM in Israel and the Palestinian Territories and analyzing retinal function and structure in CNGA3 ACHM patients from the Israeli-Palestinian population and US patients with other origins. Case series study. Patients with clinically suspected ACHM, cone dysfunction phenotypes, and unaffected family members were included. The protocol was approved by the local institutional review board and informed consent was obtained from all participants. Genetic analyses included homozygosity mapping and exome sequencing. Phenotype was assessed with electroretinography (ERG), optical coherence tomography, psychophysics, and photoaversion testing. Single nucleotide polymorphism microarray, exome analysis, DNA sequence analysis, visual function testing including ERG, and photoaversion. We identified 148 ACHM patients from 57 Israeli and Palestinian families; there were 16 CNGA3 mutations (5 novel) in 41 families and 5 CNGB3 mutations (1 novel) in 8 families. Two CNGA3 founder mutations underlie >50% of cases. These mutations lead to a high ACHM prevalence of ∼1:5000 among Arab-Muslims residing in Jerusalem. Rod ERG abnormalities (in addition to cone dysfunction) were detected in 59% of patients. Retinal structure in CNGA3 ACHM patients revealed persistent but abnormal foveal cones. Under dark- and light-adapted conditions, patients use rod-mediated pathways. Photoaversion was readily demonstrated with transition from the dark to a dim light background. Among Israeli and Palestinian patients, CNGA3 mutations are the leading cause of ACHM. Retinal structural results support the candidacy of CNGA3 ACHM for clinical trials for therapy of cone photoreceptors. Efficacy outcome measures would include chromatic light-adapted psychophysics, with attention to the photoreceptor basis of the response, and quantitation of photoaversion. Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · Jan 2015 · Ophthalmology
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    ABSTRACT: Purpose: To evaluate fixation location and oculomotor characteristics of 15 RPE65-LCA patients undergoing retinal gene therapy. Methods: Eye movements were quantified under infrared imaging of the retina while the subject fixated on a stationary target. In a subset of patients, letter recognition under retinal imaging was performed. Cortical responses to visual stimulation were measured using functional MRI in two patients before and after therapy. Results: All patients could fixate on a 1o diameter visible target in the dark. The preferred retinal locus of fixation could be at the anatomical fovea or at an extra-foveal locus. There was a wide range of oculomotor abnormalities. Natural history showed little change in oculomotor abnormalities if target illuminance was increased to maintain target visibility as the disease progressed. 11/15 study eyes with gene therapy showed no difference from baseline fixation location or instability over an average of 3.5 years followup. 4/15 eyes developed new pseudo-foveas in the treated retinal regions 9 to 12 months following therapy that persisted up to 6 years; patients used their pseudo-foveas for letter identification. fMRI studies demonstrated preservation of light sensitivity was restricted to the cortical projection zone of the pseudo-foveas. Conclusions: The slow emergence of pseudo-foveas many months following the initial increases in light sensitivity point to a substantial plasticity of the adult visual system and a complex interaction between it and the progression of underlying retinal disease. The visual significance of pseudo-foveas suggests careful consideration of treatment zones for future gene therapy trials. Copyright © 2014 by Association for Research in Vision and Ophthalmology.
    Full-text · Article · Dec 2014 · Investigative Ophthalmology & Visual Science
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    ABSTRACT: Purpose: To investigate visual function and outer and inner retinal structure in the rare form of retinal degeneration (RD) caused by TULP1 (tubby-like protein 1) mutations. Methods: Retinal degeneration patients with TULP1 mutations (n = 5; age range, 5-36 years) were studied by kinetic and chromatic static perimetry, en face autofluorescence imaging, and spectral-domain optical coherence tomography (OCT) scans. Outer and inner retinal laminar thickness were measured and mapped across the central retina. Comparisons were made with results from patients with RD associated with four ciliopathy genotypes (MAK, RPGR, BBS1, and USH2A). Results: The TULP1-RD patients were severely affected already in the first decade of life and there was rapidly progressive visual loss. No evidence of rod function was present at any age. Small central islands showed melanized retinal pigment epithelium by autofluorescence imaging and well-preserved photoreceptor laminar thickness by OCT imaging. There was extracentral loss of laminar architecture and increased inner retinal thickening. Structure-function relationships in residual foveal cone islands were made in TULP1-RD patients and in other retinopathies considered ciliopathies. Patients with TULP1-RD, unlike the others, had greater dysfunction for the degree of foveal structural preservation. Conclusions: Retinal degeneration with TULP1 mutations leads to a small central island of residual foveal cones at early ages. These cones are less sensitive than expected from the residual structure. The human phenotype is consistent with experimental evidence in the Tulp1 knockout mouse model that visual dysfunction could be complicated by abnormal processes proximal to cone outer segments.
    No preview · Article · Jul 2014 · Investigative Ophthalmology & Visual Science
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    ABSTRACT: Purpose: To investigate in vivo inner and outer retinal microstructure and effects of structural abnormalities on visual function in patients with retinal degeneration caused by ABCA4 mutations (ABCA4-RD). Methods: Patients with ABCA4-RD (n = 45; age range, 9-71 years) were studied by spectral-domain optical coherence tomography (OCT) scans extending from the fovea to 30° eccentricity along horizontal and vertical meridians. Thicknesses of outer and inner retinal laminae were analyzed. Serial OCT measurements available over a mean period of 4 years (range, 2-8 years) allowed examination of the progression of outer and inner retinal changes. A subset of patients had dark-adapted chromatic static threshold perimetry. Results: There was a spectrum of photoreceptor layer thickness changes from localized central retinal abnormalities to extensive thinning across central and near midperipheral retina. The inner retina also showed changes. There was thickening of the inner nuclear layer (INL) that was mainly associated with regions of photoreceptor loss. Serial data documented only limited change in some patients while others showed an increase in outer nuclear layer (ONL) thinning accompanied by increased INL thickening in some regions imaged. Visual function in regions both with and without INL thickening was describable with a previously defined model based on photoreceptor quantum catch. Conclusions: Inner retinal laminar abnormalities, as in other human photoreceptor diseases, can be a feature of ABCA4-RD. These changes are likely due to the retinal remodeling that accompanies photoreceptor loss. Rod photoreceptor-mediated visual loss in retinal regionswith inner laminopathy at the stages studied did not exceed the prediction from photoreceptor loss alone.
    No preview · Article · Feb 2014 · Investigative ophthalmology & visual science
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    ABSTRACT: Human X-linked blue-cone monochromacy (BCM), a disabling congenital visual disorder of cone photoreceptors, is a candidate disease for gene augmentation therapy. BCM is caused by either mutations in the red (OPN1LW) and green (OPN1MW) cone photoreceptor opsin gene array or large deletions encompassing portions of the gene array and upstream regulatory sequences that would predict a lack of red or green opsin expression. The fate of opsin-deficient cone cells is unknown. We know that rod opsin null mutant mice show rapid postnatal death of rod photoreceptors. We studied a cohort of 20 BCM patients (ages 5-58) with large deletions in the red/green opsin gene array using in vivo histology with high resolution retinal imaging. Already in the first years of life, retinal structure was not normal: there was partial loss of photoreceptors across the central retina. Remaining cone cells had detectable outer segments that were abnormally shortened. Adaptive optics imaging confirmed existence of inner segments at a spatial density greater than that expected for the residual blue cones. The evidence indicates that human cones in patients with deletions in the red/green opsin gene array can survive in reduced numbers with limited outer segment material, suggesting potential value of gene therapy for BCM.
    Full-text · Article · Sep 2013 · Human gene therapy
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    ABSTRACT: SignificanceThe first retinal gene therapy in human blindness from RPE65 mutations has focused on safety and efficacy, as defined by improved vision. The disease component not studied, however, has been the fate of photoreceptors in this progressive retinal degeneration. We show that gene therapy improves vision for at least 3 y, but photoreceptor degeneration progresses unabated in humans. In the canine model, the same result occurs when treatment is at the disease stage equivalent to humans. The study shows the need for combinatorial therapy to improve vision in the short term but also slow retinal degeneration in the long term.
    Full-text · Article · Jan 2013 · Proceedings of the National Academy of Sciences
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    ABSTRACT: Purpose: To determine the intervisit variability of kinetic visual fields and visual acuity in patients with Leber congenital amaurosis (LCA) caused by mutations in the RPE65 (Retinal Pigment Epithelium-specific protein 65kDa) gene. Methods: RPE65-LCA patients (n = 20; ages 11-40 years) were studied on at least two visits separated by fewer than 120 days using Goldmann visual field (GVF) and ETDRS visual acuity (VA) in a retrospective review. GVFs were quantified by computing the spherical coordinates of their vertices and calculating the solid angle subtended, and reported in normalized solid-angle units (nsu) as a percentage of average normal field extent. Repeatability coefficients were calculated using 95% confidence intervals on log(10)-converted variables. Results: Visual field extents in RPE65-LCA spanned a wide range from 4 to 95 nsu. The repeatability coefficient was 0.248 (log(10)nsu), suggesting cutoffs for significant change (in nsu) of +77% for improvement and -44% for worsening. VA in RPE65-LCA ranged from logMAR = 0.14 to 1.96 (20/40 to 20/1250). The repeatability coefficient was 0.170 (logMAR) (±8.5 ETDRS letters). Comparisons with published studies of ungenotyped retinitis pigmentosa showed that the RPE65-LCA patients had higher variability in kinetic field extent. VA variability in RPE65-LCA fell within reported results for retinitis pigmentosa. Conclusions: Variability data for GVF and VA are provided to permit interpretation of the significance of increases and decreases of these functional outcomes in ongoing and planned clinical trials of therapy for LCA caused by RPE65 mutations.
    No preview · Article · Jan 2013 · Investigative ophthalmology & visual science
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    ABSTRACT: Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous retinal disorder. Two forms can be distinguished clinically: complete CSNB (cCSNB) and incomplete CSNB. Individuals with cCSNB have visual impairment under low-light conditions and show a characteristic electroretinogram (ERG). The b-wave amplitude is severely reduced in the dark-adapted state of the ERG, representing abnormal function of ON bipolar cells. Furthermore, individuals with cCSNB can show other ocular features such as nystagmus, myopia, and strabismus and can have reduced visual acuity and abnormalities of the cone ERG waveform. The mode of inheritance of this form can be X-linked or autosomal recessive, and the dysfunction of four genes (NYX, GRM6, TRPM1, and GPR179) has been described so far. Whole-exome sequencing in one simplex cCSNB case lacking mutations in the known genes led to the identification of a missense mutation (c.983G>A [p.Cys328Tyr]) and a nonsense mutation (c.1318C>T [p.Arg440(∗)]) in LRIT3, encoding leucine-rich-repeat (LRR), immunoglobulin-like, and transmembrane-domain 3 (LRIT3). Subsequent Sanger sequencing of 89 individuals with CSNB identified another cCSNB case harboring a nonsense mutation (c.1151C>G [p.Ser384(∗)]) and a deletion predicted to lead to a premature stop codon (c.1538_1539del [p.Ser513Cysfs(∗)59]) in the same gene. Human LRIT3 antibody staining revealed in the outer plexiform layer of the human retina a punctate-labeling pattern resembling the dendritic tips of bipolar cells; similar patterns have been observed for other proteins implicated in cCSNB. The exact role of this LRR protein in cCSNB remains to be elucidated.
    Full-text · Article · Dec 2012 · The American Journal of Human Genetics
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    ABSTRACT: Purpose: To determine the proportion of male patients presenting simplex retinal degenerative disease (RD: retinitis pigmentosa [RP] or cone/cone-rod dystrophy [COD/CORD]) with mutations in the X-linked retinal degeneration genes RPGR and RP2. Methods: Simplex males were defined as patients with no known affected family members. Patients were excluded if they had a family history of parental consanguinity. Blood samples from a total of 214 simplex males with a diagnosis of retinal degeneration were collected for genetic analysis. The patients were screened for mutations in RPGR and RP2 by direct sequencing of PCR-amplified genomic DNA. Results: We identified pathogenic mutations in 32 of the 214 patients screened (15%). Of the 29 patients with a diagnosis of COD/CORD, four mutations were identified in the ORF15 mutational hotspot of the RPGR gene. Of the 185 RP patients, three patients had mutations in RP2 and 25 had RPGR mutations (including 12 in the ORF15 region). Conclusions: This study represents mutation screening of RPGR and RP2 in the largest cohort, to date, of simplex males affected with RP or COD/CORD. Our results demonstrate a substantial contribution of RPGR mutations to retinal degenerations, and in particular, to simplex RP. Based on our findings, we suggest that RPGR should be considered as a first tier gene for screening isolated males with retinal degeneration.
    Full-text · Article · Nov 2012 · Investigative ophthalmology & visual science
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    ABSTRACT: The GUCY2D gene encodes retinal membrane guanylyl cyclase (RetGC1), a key component of the phototransduction machinery in photoreceptors. Mutations in GUCY2D cause Leber congenital amaurosis type 1 (LCA1), an autosomal recessive human retinal blinding disease. The effects of RetGC1 deficiency on human rod and cone photoreceptor structure and function are currently unknown. To move LCA1 closer to clinical trials, we characterized a cohort of patients (ages 6 months-37 years) with GUCY2D mutations. In vivo analyses of retinal architecture indicated intact rod photoreceptors in all patients but abnormalities in foveal cones. By functional phenotype, there were patients with and those without detectable cone vision. Rod vision could be retained and did not correlate with the extent of cone vision or age. In patients without cone vision, rod vision functioned unsaturated under bright ambient illumination. In vitro analyses of the mutant alleles showed that in addition to the major truncation of the essential catalytic domain in RetGC1, some missense mutations in LCA1 patients result in a severe loss of function by inactivating its catalytic activity and/or ability to interact with the activator proteins, GCAPs. The differences in rod sensitivities among patients were not explained by the biochemical properties of the mutants. However, the RetGC1 mutant alleles with remaining biochemical activity in vitro were associated with retained cone vision in vivo. We postulate a relationship between the level of RetGC1 activity and the degree of cone vision abnormality, and argue for cone function being the efficacy outcome in clinical trials of gene augmentation therapy in LCA1.
    No preview · Article · Oct 2012 · Human Molecular Genetics
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    ABSTRACT: We investigated the retinal disease due to mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in human patients and in an Rpgr conditional knockout (cko) mouse model. XLRP patients with RPGR-ORF15 mutations (n = 35, ages at first visit 5-72 years) had clinical examinations, and rod and cone perimetry. Rpgr-cko mice, in which the proximal promoter and first exon were deleted ubiquitously, were back-crossed onto a BALB/c background, and studied with optical coherence tomography and electroretinography (ERG). Retinal histopathology was performed on a subset. Different patterns of rod and cone dysfunction were present in patients. Frequently, there were midperipheral losses with residual rod and cone function in central and peripheral retina. Longitudinal data indicated that central rod loss preceded peripheral rod losses. Central cone-only vision with no peripheral function was a late stage. Less commonly, patients had central rod and cone dysfunction, but preserved, albeit abnormal, midperipheral rod and cone vision. Rpgr-cko mice had progressive retinal degeneration detectable in the first months of life. ERGs indicated relatively equal rod and cone disease. At late stages, there was greater inferior versus superior retinal degeneration. RPGR mutations lead to progressive loss of rod and cone vision, but show different patterns of residual photoreceptor disease expression. Knowledge of the patterns should guide treatment strategies. Rpgr-cko mice had onset of degeneration at relatively young ages and progressive photoreceptor disease. The natural history in this model will permit preclinical proof-of-concept studies to be designed and such studies should advance progress toward human therapy.
    Full-text · Article · Jul 2012 · Investigative ophthalmology & visual science
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    ABSTRACT: To measure macular visual function in patients with unstable fixation, to define the photoreceptor source of this function, and to estimate its test-retest repeatability as a prerequisite to clinical trials. Patients (n = 38) with ABCA4-associated retinal degeneration (RD) or with retinitis pigmentosa (RP) were studied with retina-tracking microperimetry along the foveo-papillary profile between the fovea and the optic nerve head, and point-by-point test-retest repeatability was estimated. A subset with foveal fixation was also studied with dark-adapted projection perimetry using monochromatic blue and red stimuli along the horizontal meridian. Macular function in ABCA4-RD patients transitioned from lower sensitivity at the parafovea to higher sensitivity in the perifovea. RP patients had the inverse pattern. Red-on-red microperimetric sensitivities successfully avoided ceiling effects and were highly correlated with absolute sensitivities. Point-by-point test-retest limits (95% confidence intervals) were ±4.2 dB; repeatability was not related to mean sensitivity, eccentricity from the fovea, age, fixation location, or instability. Repeatability was also not related to the local slope of sensitivity and was unchanged in the parapapillary retina. Microperimetry allows reliable testing of macular function in RD patients without foveal fixation in longitudinal studies evaluating natural disease progression or efficacy of therapeutic trials. A single estimate of test-retest repeatability can be used to determine significant changes in visual function at individual retinal loci within diseased regions that are homogeneous and those that are heterogeneous and also in transition zones at high risk for disease progression.
    Full-text · Article · Feb 2012 · Investigative ophthalmology & visual science
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    ABSTRACT: Autosomal recessive retinitis pigmentosa (RP), a heterogeneous group of degenerations of the retina, can be due to mutations in the MFRP (membrane-type frizzled-related protein) gene. A patient with RP with MFRP mutations, one of which is novel and the first splice site mutation reported, was characterized by noninvasive retinal and visual studies. The phenotype, albeit complex, suggested that this retinal degeneration may be a candidate for gene-based therapy. Proof-of-concept studies were performed in the rd6 Mfrp mutant mouse model. The fast-acting tyrosine-capsid mutant AAV8 (Y733F) vector containing the small chicken β-actin promoter driving the wild-type mouse Mfrp gene was used. Subretinal vector delivery on postnatal day 14 prevented retinal degeneration. Treatment rescued rod and cone photoreceptors, as assessed by electroretinography and retinal histology at 2 months of age. This AAV-mediated gene delivery also resulted in robust MFRP expression predominantly in its normal location within the retinal pigment epithelium apical membrane and its microvilli. The clinical features of MFRP-RP and our preliminary data indicating a response to gene therapy in the rd6 mouse suggest that this form of RP is a potential target for gene-based therapy.
    Full-text · Article · Dec 2011 · Human gene therapy

Publication Stats

4k Citations
397.57 Total Impact Points

Institutions

  • 2008-2015
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 2003-2015
    • University of Pennsylvania
      • Department of Ophthalmology
      Filadelfia, Pennsylvania, United States
  • 2007
    • University of Iowa
      Iowa City, Iowa, United States