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

Injury Induced by Chemical Warfare Agents: Characterization and Treatment of Ocular Tissues Exposed to Nitrogen Mustard

PURPOSE. Mustard agents are highly toxic and abundant warfare chemicals, primarily affecting ocular tissues, with no specific treatment antidote. The purpose of the present study was to examine the efficacy of novel metallocomplexes, known to inhibit the formation of highly reactive free radicals, to reduce ocular injury induced by nitrogen mustard (NM). METHODS. One eye in each of 72 rabbits was exposed to 1% to 2% NM. Topical treatment with eye drops of a metallocomplex-either zinc-or gallium-desferrioxamine (Zn/DFO and Ga/DFO)-was compared with treatment with saline, zinc (chloride), or DFO alone. Examiners masked to the treatment groups assessed the extent of ocular injury and the response to treatment using clinical, histologic, and biochemical criteria. RESULTS. Exposure to NM followed by administration of carrier alone (saline) caused severe and long-lasting injury to ocular anterior segment structures. Treatment with either Zn/DFO or Ga/DFO yielded marked protection (52%-64%), including faster healing of corneal epithelial erosions, less scarring and neovascularization, decreased inflammation in the anterior chamber, better maintenance of intraocular pressure, and less severe changes in the iris and lens. These were also associated with better preservation of systemic antioxidant status. Zinc or DFO alone afforded lower levels of protection. No toxic effects of these complexes were observed. CONCLUSIONS. It is suggested that Zn/DFO or Ga/DFO, by virtue of their enhanced ability to infiltrate cells and inhibit transition metal-dependent formation of free radicals through the combined push-pull mechanism, be considered as a basis for treatment of mustard injuries. (Invest Ophthalmol Vis Sci

Molecular Anthropology Meets Genetic Medicine to Treat Blindness in the North African Jewish Population: Human Gene Therapy Initiated in Israel

Abstract The history of the North African Jewish community is ancient and complicated with a number of immigration waves and persecutions dramatically affecting its population size. A decade-long process in Israel of clinicalmolecular screening of North African Jews with incurable autosomal recessive blindness led to the identification of a homozygous splicing mutation (c.95-2A > T; IVS2-2A > T) in RPE65, the gene encoding the isomerase that catalyzes a key step in the retinoid-visual cycle, in patients from 10 unrelated families. A total of 33 patients (four now deceased) had the severe childhood blindness known as Leber congenital amaurosis (LCA), making it the most common cause of retinal degeneration in this population. Haplotype analysis in seven of the patients revealed a shared homozygous region, indicating a population-specific founder mutation. The age of the RPE65 founder mutation was estimated to have emerged 100-230 (mean, 153) generations ago, suggesting it originated before the establishment of the Jewish community in North Africa. Individuals with this RPE65 mutation were characterized with retinal studies to determine if they were candidates for gene replacement, the recent and only therapy to date for this otherwise incurable blindness. The step from molecular anthropological studies to application of genetic medicine was then taken, and a representative of this patient subgroup was treated with subretinal rAAV2-RPE65 gene therapy. An increase in vision was present in the treated area as early as 15 days after the intervention. This process of genetically analyzing affected isolated populations as a screen for genebased therapy suggests a new paradigm for disease diagnosis and treatment

Immunological Properties of Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cells

Summary: Age-related macular degeneration is caused by dysfunction and loss of retinal pigment epithelium (RPE) cells, and their transplantation may rescue visual functions and delay disease progression. Human embryonic stem cells (hESCs) may be an unlimited source of RPE cells for allotransplantation. We analyzed the immunomodulatory properties of hESC-derived RPE (hESC-RPE) cells, and showed that they inhibited T cell responses. Co-culture experiments showed that RPE cells inhibited interfon-γ secretion and proliferation of activated T cells. Furthermore, hESC-RPE cells enhanced T cell apoptosis and secretion of the anti-inflammatory cytokine interleukin-10 (IL-10). In addition, RPE cells altered the expression of T cell activation markers, CD69 and CD25. RPE cells transplanted into RCS rats without immunosuppression survived, provided retinal rescue, and enhanced IL-10 blood levels. Our data suggest that hESC-RPE cells have immunosuppressive properties. Further studies will determine if these properties are sufficient to alleviate the need for immunosuppression therapy after their clinical allotransplantation. : In this article, Reubinoff and colleagues describe the immunomodulatory properties of hESC-RPE cells. They show that the RPE cells inhibit IFN-γ secretion and proliferation of T cells and enhance T cells apoptosis and secretion of IL-10. In the absence of immunosuppression therapy, RPE cells survive, provide retinal rescue, and enhance IL-10 blood levels in a rat model of retinal degeneration. These findings are relevant to designing immunosuppressive regimens for RPE cell allotransplantation therapies. Keywords: retinal pigment epithelium, human embryonic stem cells, immunomodulation, immune-privileg

Retinal Structure and Function in a Knock-in Mouse Model for the FAM161A-p.Arg523∗ Human Nonsense Pathogenic Variant

Purpose: Pathogenic variants in FAM161A are the most common cause of retinitis pigmentosa in Israel. Two founder pathogenic variants explain the vast majority of cases of Jewish origin, 1 being a nonsense variant (p.Arg523∗). The aim of this study was to generate a knock-in (KI) mouse model harboring the corresponding p.Arg512∗ pathogenic variant and characterize the course of retinal disease. Design: Experimental study of a mouse animal model. Subjects/Participants/Controls: A total of 106 Fam161a knock-in mice and 29 wild-type mice with C57BL/6J background particiapted in this study. Methods: Homozygous Fam161a p.Arg512∗ KI mice were generated by Cyagen Biosciences. Visual acuity (VA) was evaluated using optomotor tracking response and retinal function was assessed by electroretinography (ERG). Retinal structure was examined in vivo using OCT and fundus autofluorescence imaging. Retinal morphometry was evaluated by histologic and immunohistochemical (IHC) analyses. Main Outcome Measures: Visual and retinal function assessments, clinical imaging examinations, quantitative histology, and IHC studies of KI as compared with wild-type (WT) mice retinas. Results: The KI model was generated by replacing 3 bp, resulting in p.Arg512∗. Homozygous KI mice that had progressive loss of VA and ERG responses until the age of 18 months, with no detectable response at 21 months. OCT showed complete loss of the outer nuclear layer at 21 months. Fundus autofluorescence imaging revealed progressive narrowing of blood vessels and formation of patchy hyper-autofluorescent and hypo-autofluorescent spots. Histologic analysis showed progressive loss of photoreceptor nuclei. Immunohistochemistry staining showed Fam161a expression mainly in photoreceptors cilia and the outer plexiform layer (OPL) in WT mice retinas, whereas faint expression was evident mainly in the cilia and OPL of KI mice. Conclusions: The Fam161a - p.Arg512∗ KI mouse model is characterized by widespread retinal degeneration with relatively slow progression. Surprisingly, disease onset is delayed and progression is slower compared with the previously reported knock-out model. The common human null mutation in the KI mouse model is potentially amenable for correction by translational read-through-inducing drugs and by gene augmentation therapy and RNA editing, and can serve to test these treatments as a first step toward possible application in patients. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article

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

Degeneration Modulates Retinal Response to Transient Exogenous Oxidative Injury

<div><p>Purpose</p><p>Oxidative injury is involved in retinal and macular degeneration. We aim to assess if retinal degeneration associated with genetic defect modulates the retinal threshold for encountering additional oxidative challenges.</p><p>Methods</p><p>Retinal oxidative injury was induced in degenerating retinas (rd10) and in control mice (WT) by intravitreal injections of paraquat (PQ). Retinal function and structure was evaluated by electroretinogram (ERG) and histology, respectively. Oxidative injury was assessed by immunohistochemistry for 4-Hydroxy-2-nonenal (HNE), and by Thiobarbituric Acid Reactive Substances (TBARS) and protein carbonyl content (PCC) assays. Anti-oxidant mechanism was assessed by quantitative real time PCR (QPCR) for mRNA of antioxidant genes and genes related to iron metabolism, and by catalase activity assay.</p><p>Results</p><p>Three days following PQ injections (1 µl of 0.25, 0.75, and 2 mM) the average ERG amplitudes decreased more in the WT mice compared with the rd10 mice. For example, following 2 mM PQ injection, ERG amplitudes reduced 1.84-fold more in WT compared with rd10 mice (p = 0.02). Injection of 4 mM PQ resulted in retinal destruction. Altered retina morphology associated with PQ was substantially more severe in WT eyes compared with rd10 eyes. Oxidative injury according to HNE staining and TBARS assay increased 1.3-fold and 2.1-fold more, respectively, in WT compared with rd10 mice. At baseline, prior to PQ injection, mRNA levels of antioxidant genes (<i>Superoxide Dismutase1, Glutathione Peroxidase1, Catalase</i>) and of <i>Transferrin</i> measured by quantitative PCR were 2.1–7.8-fold higher in rd10 compared with WT mice (p<0.01 each), and catalase activity was 1.7-fold higher in rd10 (p = 0.0006).</p><p>Conclusions</p><p>This data suggests that degenerating rd10 retinas encounter a relatively lower degree of damage in response to oxidative injury compared with normal retinas. Constitutive up-regulation of the oxidative defense mechanism in degenerating retinas may confer such relative protection from oxidative injury.</p></div

Scotopic b-wave ERG responses following intravitreal injection of PQ.

<p>ERGs were recorded three days following injection of 4(A,B), 2 mM (C,D), 0.75 mM (E,F), or 0.25 mM (G,H) of PQ in one eye and PBS in the fellow eye of wild type (WT) and rd10 mice (n = 10–22 in each group). Y-axis shows amplitude in microvolt while the x-axis shows the stimulus intensity.</p

Retinal Expression of antioxidant genes in rd10 and WT mice.

<p>(A) mRNA levels of anti-oxidant enzymes in normal and degenerating retinas. <i>SOD1</i>, <i>GPX1,</i> and <i>CAT</i> expression levels were measured using QPCR (rd10 n = 7 pairs, WT n = 4 pairs). (B) Catalase activity evaluated in retinas of three-week-old WT and rd10 mice. *p<0.05 in comparison to WT (n = 5 in each group).</p

Protein carbonyl content (PCC) in mice retinas following PQ injection.

<p>Protein carbonylation was measured to assess oxidative retinal injury to proteins. It was assessed in retinas of rd10 and WT mice injected with 1 µl of 2 mM PQ or PBS. In both strains PQ injections caused an insignificant 1.35 fold increase of PCC. *p = 0.009 comparing control (PBS) rd10 with WT retinas (n = 5 in each group).</p