Targeting ON-bipolar cells by AAV gene therapy stably reverses LRIT3-congenital stationary night blindness.

SignificanceCanine models of inherited retinal diseases have helped advance adeno-associated virus (AAV)-based gene therapies targeting specific cells in the outer retina for treating blinding diseases in patients. However, therapeutic targeting of diseases such as congenital stationary night blindness (CSNB) that exhibit defects in ON-bipolar cells (ON-BCs) of the midretina remains underdeveloped. Using a leucine-rich repeat, immunoglobulin-like and transmembrane domain 3 (LRIT3) mutant canine model of CSNB exhibiting ON-BC dysfunction, we tested the ability of cell-specific AAV capsids and promotors to specifically target ON-BCs for gene delivery. Subretinal injection of one vector demonstrated safety and efficacy with robust and stable rescue of electroretinography signals and night vision up to 1 y, paving the way for clinical trials in patients.

RPE65-Associated Retinal Dystrophies: Phenotypes and Treatment Effects with Voretigene Neparvovec.

Retinal dystrophies linked to the RPE65 gene are mostly fast-progressing retinal diseases, with childhood onset of night blindness and progressive visual loss up to the middle adult age. Rare phenotypes linked to this gene are known with congenital stationary night blindness or slowly progressing retinitis pigmentosa, as well as an autosomal dominant c.1430A>G (p.Asp477Gly) variant. This review gives an overview of the current knowledge of the clinical phenotypes, as well as experience with the efficacy and safety of the approved gene augmentation therapy voretigene neparvovec.

Congenital Stationary Night Blindness: Clinical and Genetic Features.

Congenital stationary night blindness (CSNB) is an inherited retinal disease (IRD) that causes night blindness in childhood with heterogeneous genetic, electrophysical, and clinical characteristics. The development of sequencing technologies and gene therapy have increased the ease and urgency of diagnosing IRDs. This study describes seven Taiwanese patients from six unrelated families examined at a tertiary referral center, diagnosed with CSNB, and confirmed by genetic testing. Complete ophthalmic exams included best corrected visual acuity, retinal imaging, and an electroretinogram. The effects of identified novel variants were predicted using clinical details, protein prediction tools, and conservation scores. One patient had an autosomal dominant CSNB with a RHO variant; five patients had complete CSNB with variants in GRM6, TRPM1, and NYX; and one patient had incomplete CSNB with variants in CACNA1F. The patients had Riggs and Schubert-Bornschein types of CSNB with autosomal dominant, autosomal recessive, and X-linked inheritance patterns. This is the first report of CSNB patients in Taiwan with confirmed genetic testing, providing novel perspectives on molecular etiology and genotype-phenotype correlation of CSNB. Particularly, variants in TRPM1, NYX, and CACNA1F in our patient cohort have not previously been described, although their clinical significance needs further study. Additional study is needed for the genotype-phenotype correlation of different mutations causing CSNB. In addition to genetic etiology, the future of gene therapy for CSNB patients is reviewed and discussed.

Melanoma-associated retinopathy.

Melanoma-associated retinopathy (MAR) is a rare paraneoplastic autoimmune manifestation of cutaneous malignant melanoma. Patients classically present with acute onset night blindness, positive visual phenomena and visual field defects, and typically have significantly reduced quality of life as a result. Early recognition of MAR is of prognostic significance as it can precede the diagnosis of primary or metastatic malignant melanoma, and early treatment can lower the risk of irreversible immunological damage to the retinal cells with improved visual outcomes. The focus of our review article is therefore to raise awareness of MAR and present the latest evidence relating to the investigation and management of this condition.

Sensing through Non-Sensing Ocular Ion Channels.

Ion channels are membrane-spanning integral proteins expressed in multiple organs, including the eye. In the eye, ion channels are involved in various physiological processes, like signal transmission and visual processing. A wide range of mutations have been reported in the corresponding genes and their interacting subunit coding genes, which contribute significantly to an array of blindness, termed ocular channelopathies. These mutations result in either a loss- or gain-of channel functions affecting the structure, assembly, trafficking, and localization of channel proteins. A dominant-negative effect is caused in a few channels formed by the assembly of several subunits that exist as homo- or heteromeric proteins. Here, we review the role of different mutations in switching a "sensing" ion channel to "non-sensing," leading to ocular channelopathies like Leber's congenital amaurosis 16 (LCA16), cone dystrophy, congenital stationary night blindness (CSNB), achromatopsia, bestrophinopathies, retinitis pigmentosa, etc. We also discuss the various in vitro and in vivo disease models available to investigate the impact of mutations on channel properties, to dissect the disease mechanism, and understand the pathophysiology. Innovating the potential pharmacological and therapeutic approaches and their efficient delivery to the eye for reversing a "non-sensing" channel to "sensing" would be life-changing.

[Overview of Congenital Stationary Night Blindness with Predominantly Normal Fundus Appearance]. / Überblick über die kongenitale stationäre Nachtblindheit mit überwiegend normalem Fundus.

Congenital stationary night blindness (CSNB) is a clinically and genetically heterogeneous group of non-progressive retinal disorder with largely normal fundus appearance. The mode of inheritance can be autosomal dominant (adCSNB), autosomal recessive (arCSNB) or X-chromosomal (XLCSNB). Additional ocular signs can be myopia, hyperopia, strabismus, nystagmus and reduced visual acuity. The Riggs and Schubert-Bornschein form of CSNB can be discriminated by electroretinography. While the Riggs form represents a dysfunction of the rods, a signal transmission defect from photoreceptors to bipolar cell is described in patients with the more frequently occurring Schubert-Bornschein form. The Schubert-Bornschein form can be further divided into incomplete (icCSNB) and complete (cCSNB) showing different electroretinograms (ERGs). While patients with cCSNB show a dysfunction of the ON-signaling pathway, patients with icCSNB show a dysfunction of the ON- and OFF-signaling pathways, affecting visual acuity as well. Using classical linkage, candidate gene analyses and more recent next-generation sequencing approaches, to date, mutations in 13 different genes have been associated with this disease. In vitro and in vivo models showed a correlation of the phenotype of patients with the expression, protein localization and function of the respective molecules: genes, mutated in patients with the Riggs form of CSNB have an important role in the rod phototransduction cascade. Genes mutated in patients with icCSNB, code for proteins important for glutamate neurotransmitter release at the synaptic cleft of the photoreceptors. Genes mutated in patients with cCSNB, code for proteins important for glutamate uptake and further signal transmission to the ON-bipolar cells. Preliminary in vivo studies showed that CSNB may be cured by gene therapy. These studies concerning CSNB are important for the precise diagnosis of patients with this disease, but are also helpful in deciphering key molecules essential for signal transmission from photoreceptors to bipolar cells. So far, it is a poorly understood field.

Characterization of Ribozymes Targeting a Congenital Night Blindness Mutation in Rhodopsin Mutation.

The G90D mutation in the rhodopsin gene leads to autosomal dominant congenital stationary night blindness (CSNB) in patients. This occurs because the G90D mutant protein cannot efficiently bind chromophore and is constitutively active. To combat this mutation, we designed and characterized two different hammerhead ribozymes to cleave G90D transcript. In vitro testing showed that the G90D1 ribozyme efficiently and specifically cleaved the mutant transcript while G90D2 cleaved both WT and mutant transcript. AAV-mediated delivery of G90D1 under the control of the mouse opsin promoter (MOP500) to G90D transgenic eyes showed that the ribozyme partially retarded the functional degeneration (as measured by electroretinography [ERG]) associated with this mutation. These results suggest that with additional optimization, ribozymes may be a useful part of the gene therapy knockdown strategy for dominant retinal disease.

Extended functional rescue following AAV gene therapy in a canine model of LRIT3-congenital stationary night blindness.

Congenital stationary night blindness (CSNB) is a group of inherited retinal diseases in which either rod-to-ON-bipolar cell (ON-BC) signaling, or rod function is affected leading to impaired vision under low light conditions. One type of CSNB is associated with defects in genes (NYX, GRM6, TRPM1, GPR179, and LRIT3) involved in the mGluR6 signaling cascade at the ON-BC dendritic tips. We have previously characterized a canine model of LRIT3-CSNB and demonstrated short-term safety and efficacy of an ON-BC targeting AAV-LRIT3 (AAVK9#4-shGRM6-cLRIT3-WPRE) gene therapy. Herein, we demonstrate long-term functional recovery and molecular restoration following subretinal injection of the ON-BC targeting AAV-LRIT3 vector in all eight treated eyes for up to 32 months. Following subretinal administration of the therapeutic vector, expression of the LRIT3 transgene, as well as restoration of mGluR6 signaling cascade member TRPM1, were confirmed in the outer plexiform layer (OPL) of the treated area. However, further investigation of the transgene LRIT3 transcript expression by RNA in situ hybridization (RNA-ISH) revealed off-target expression in non-BCs including the photoreceptors, inner nuclear, and ganglion cell layers, despite the use of a mutant AAVK9#4 capsid and an improved mGluR6 promoter designed to specifically transduce and promote expression in ON-BCs. While the long-term therapeutic potential of AAVK9#4-shGRM6-cLRIT3-WPRE is promising, we highlight the necessity for further optimization of AAV-LRIT3 therapy in the canine CSNB model prior to its clinical application.

Night Blindness in Cystic Fibrosis: The Key Role of Vitamin A in the Digestive System.

Vitamin A is a fundamental micronutrient that regulates various cellular patterns. Vitamin A deficiency (VAT) is a worldwide problem and the primary cause of nocturnal blindness especially in low income countries. Cystic fibrosis (CF) is a known risk factor of VAD because of liposoluble vitamin malabsorption due to pancreatic insufficiency. We describe a case of a 9-year-old girl who experienced recurrent episodes of nocturnal blindness due to profound VAD. This little girl is paradigmatic for the explanation of the key role of the gut-liver axis in vitamin A metabolism. She presents with meconium ileus at birth, requiring intestinal resection that led to a transient intestinal failure with parenteral nutrition need. In addition, she suffered from cholestatic liver disease due to CF and intestinal failure-associated liver disease. The interaction of pancreatic function, intestinal absorption and liver storage is fundamental for the correct metabolism of vitamin A.

Congenital stationary night blindness: an analysis and update of genotype-phenotype correlations and pathogenic mechanisms.

Congenital stationary night blindness (CSNB) refers to a group of genetically and clinically heterogeneous retinal disorders. Seventeen different genes with more than 360 different mutations and more than 670 affected alleles have been associated with CSNB, including genes coding for proteins of the phototransduction cascade, those important for signal transmission from the photoreceptors to the bipolar cells or genes involved in retinoid recycling in the retinal pigment epithelium. This article describes the phenotypic characteristics of different forms of CSNB that are necessary for accurate diagnosis and to direct and improve genetic testing. An overview of classical and recent methods used to identify specific CSNB genotypes is provided and a meta-analysis of all previously published and novel data is performed to determine the prevalence of disease-causing mutations. Studies of the underlying molecular pathogenic mechanisms based on cell culture techniques and animal studies are outlined. The article highlights how the study of CSNB has increased understanding of the mechanisms of visual signalling in the retina, likely to prove important in developing future treatments for CSNB and other retinal disorders.

Functional and structural recovery of the retina after gene therapy in the RPE65 null mutation dog.

PURPOSE: To assess the efficacy of AAV-mediated gene therapy to restore vision in a large number of RPE65(-/-) dogs and to determine whether systemic and local side effects are caused by the treatment. METHODS: Normal RPE65 dog cDNA was subcloned into an rAAV vector under control of a cytomegalovirus promoter, and an AAV.GFP control vector was also produced with the titers 2 x 10(12) particles/mL and 2 x 10(10) transducing U/mL, respectively. RPE65(-/-) dogs, aged 4 to 30 months were treated with subretinal injections of the AAV.RPE65 and control vectors, respectively, in each eye, and three 24- to 30-month-old normal control dogs with the latter. Baseline and postoperative systemic and ophthalmic examinations, blood screenings, vision testing, and electroretinography (ERG) were performed. Two RPE65(-/-) dogs were killed at 3 and 6 months after treatment for morphologic examination of the retinas. RESULTS: RPE65(-/-) dogs were practically blind from birth with nonrecordable or low-amplitude ERGs. Construct injections or sham surgeries were performed in 28 eyes; 11 were injected subretinally with the AAV.RPE65 construct. ERGs at 3 months after surgery showed that in the latter eyes, dark-adapted b-wave amplitudes recovered to an average of 28% of normal, and light adapted b-wave amplitudes to 32% of normal. ERG amplitudes were not reduced during a 6- to 9-month follow-up. No systemic side effects were observed, but uveitis developed in nine AAV.RPE65-treated eyes. No uveitis was observed in the eyes treated with the control vector. Immunocytochemistry showed expression of RPE65 in the retinal pigment epithelium (RPE) of AAV.RPE65-treated eyes. Fluorescence microscopy showed expression of green fluorescent protein (GFP) in the RPE and, to a lesser extent, in the neural retinas of AAV.GFP-treated eyes. Ultrastructurally, a reversal of RPE lipid droplet accumulation was observed at the AAV.RPE65 transgene injection site, but not at the site of injection of the control vector. CONCLUSIONS: In 10 of 11 treated RPE65(-/-) eyes, gene transfer resulted in development of vision, both subjectively apparent by loss of nystagmus, and objectively recorded by ERG. Structurally, there was reversal of lipid droplet accumulation in the RPE. Uveitis developed in 75% of the transgene-treated eyes, a complication possibly due to an immunopathogenic response to the RPE65 molecule.

Through a shade darkly.

A 43-year-old man complained of difficulty seeing in dim light (nyctalopia). A prolonged photostress test and abnormal electroretinogram confirmed retinal rather than optic nerve dysfunction. Vitamin A deficiency secondary to remote ileal-jejunal bypass was diagnosed, and his visual symptoms and signs reversed with oral vitamin A supplementation.

An ethnographic study of night blindness "ratauni" among women in the Terai of Nepal.

Night blindness is the most common ocular condition representing moderate-to-severe vitamin A deficiency in children. Very little, however, is known about maternal night blindness, which has recently been reported to occur frequently during pregnancy in parts of south-east Asia. In Nepal, the prevalence of night blindness is reported to be 16%. We carried out an ethnographic study of night blindness during pregnancy in the south-eastern, rural plains of Nepal as preliminary research for a case-control study of the determinants of this condition. The purpose of the research was to identify local terms and concepts of night blindness and to examine women's perceptions of its causes, symptoms, severity, and consequences during pregnancy. Data collection involved in-depth interviews, case studies, unstructured observations and structured anthropologic methods, such as free listing and quick sort ranking. Women considered night blindness to be an important illness of pregnancy, ranking it second (to vaginal bleeding) in perceived severity from a list of 15 "women's illnesses". Local terms for night blindness were identified in three different languages from the region. Informants described a complex ethnomedical model of night blindness that included causes, symptomatology, and treatment alternatives. However, there was no perceived link between food intake and the occurrence of night blindness. The major causes of night blindness were attributed to pregnancy, weakness, or "hotness". Some women sought treatment for the condition but most women chose not to treat it since they believed that it was a transient condition of pregnancy. Interviews with women who had previously experienced night blindness and home-based observations of women exhibiting concurrent night blindness showed that it adversely affected their activity patterns, especially those related to child care and food preparation. Night blindness increased reliance on family members to perform various domestic chores and was also associated with personal injury and accidents. The findings of this study have relevance for women's reproductive health and nutrition throughout the Indian sub-continent. A simple history of night blindness may be a practical tool to identify women with nutritional and health risks. Maternal night blindness should be more routinely investigated in vitamin A deficient areas of the world, both to define the magnitude of the problem, and to develop programs/interventions that specifically target this population.

[Melanoma-associated retinopathy. Apropos of a case and review of the literature]. / Rétinopathie associée au mélanome cutané. A propos d'un cas et revue de la littérature.

We describe here a case of melanoma-associated retinopathy. In 1993, a 60 year-old man had a cutaneous malignant melanoma surgically removed from the third right toe (thickness 3.15 mm; level IV). One year later he complained suddenly of photopsias, shimmering lights and night blindness of the left eye. Visual acuity and fundus examination were normal. The left visual field showed a tubular aspect. The photopic electroretinogram (ERG) was negative, and the scotopic one was flat. Six weeks later the same symptoms occurred in the right eye. One month later, inguinal lymph nodes were invaded with cancer cells. The association of metastatic melanoma, ocular functional signs and ERG's abnormalities suggested the diagnosis of melanoma-associated retinopathy. This paraneoplastic syndrome is very rare: only seven cases have been described. Antibodies against retinal bipolar cells have shown up in three cases. Treatment is yet to be discovered.

[Congenital stationary night blindness]. / Wrodzona niepostepujaca slepota nocna.

Authors present diagnostic procedures and dinical features of the congenital stationary night blindness (CSNB) in 19 patients. Effective therapy of the concomitant ophthalmological pathologies usually improves patient's vision ability.

[Historical milestones in the treatment of night blindness]. / Geschichtliche Meilensteine in der Behandlung der Nachtblindheit.

Most cases of night-blindness (nyctalopia or hemeralopia) do occur without an apparent organic eye-disease. In the past one spoke of essential or epidemic night-blindness. It is caused by a vitamin deficiency, and is a result of failing dark adaptation; it may lead to xerophthalmia, and finally to a complete permanent blindness, if not treated in time with vitamin A or vitamin A containing food (butter, egg-yolk, fish-liver oil). From time immemorial the healing effects of the intake of liver from fish and various animals for night-blindness has been reported from countries all over the world. In medical literature it has been recommended in the Papyrus Ebers (ca. 1500 B.C.), by the old Greek writers, from Hippocrates to Galen, and later to Oribasius and others. In the early sixteenth century Jac. Bontius (1592-1631) learned this therapy from empiric folk-medicine and advocated shark-liver as a specific medicine. Notwithstanding scattered reports of the dramatic favourable result of liver-treatment in patients with night-blindness, it would last until experimental research with a fat-poor diet led to the discovery (1913) and identification of vitamin A in our century, and the high vitamin A content of liver was established. Thus recognizing the value of the old liver-treatment, finally vitamin A was introduced in official ophthalmology. So an age-old, nearly universal favourable experience of empiric medicine had been neglected to the detriment of countless sufferers of night-blindness. Today systematic administration in cases of impending blindness, especially in some Asiatic areas, has already prevented the development of lasting blindness on a large scale.

A historical perspective on the early treatment of night blindness and the use of dubious and unproven treatment strategies for patients with retinitis pigmentosa.

Retinitis pigmentosa (RP) is a form of inherited night blindness. Over decades, various dubious treatment strategies that lacked sufficient theoretically sound underpinnings were explored. Initially they were enthusiastically promoted and subsequently discredited. It is apparent that many were predicated on the erroneous assumption that the primary cause of RP was related to impairment of the retinal circulation. Herein, several of these strategies are reviewed and critiqued. Reasons why clinicians may have been deceived into overzealous interpretations of their treatment methods are explored. The examples disclosed should serve as a note of caution for current investigators to guard against self-deception when exploring newly developed treatment strategies.

Reduction of vitamin A deficiency and anemia in pregnancy after implementing proposed prenatal nutritional assistance.

INTRODUCTION: Micronutrient deficiency is an unquestionable public health problem, specially anemia and vitamin A deficiency (VAD). This is due to the collective dimension of these carencies, which reflects on morbimortality rates in the maternal and infant group. OBJECTIVE: to evaluate the impact of a proposal for prenatal nutritional assistance, comparing the prevalence of anemia and VAD, in pre-intervention (GI) and intervention (GII) groups. METHODS: this is a prospective intervention study in a cohort of pregnant women. The GI group was made up of 225 the GII group of 208 pregnant adults and their respective newborns, attended a Public Maternity Ward in Rio de Janeiro, Brazil. Concentration of hemoglobin was used to diagnose anemia and a standardized interview to diagnose night blindness (XN). RESULTS AND CONCLUSION: after adjusting for confounding variables, through logistic regression, the protective effect of intervention at the onset of anemia (OR = 0.420; IC 95% = 0.251-0.702), with a significant reduction in prevalence, of 28.4% in the GI to 16.8% in the GII, also observed at the onset of XN (OR = 0.377; IC95% = 0.187- 0.759), with a reduction in prevalence of 18.7 % in the GI to 6.2% in the GII. Nutritional intervention has a beneficial effect on maternal health, reducing nutritional deficiencies most prevalent during pregnancy and the impact of these on the obstetric ailment.