An inherited night blindness in Wiltshire sheep

Twelve cases of adult-onset blindness were identified in a flock of 130 polled Wiltshire sheep in New Zealand over a 3-year period. Affected sheep developed night blindness between 2 and 3 years of age, which progressed to complete blindness by 4 to 5 years of age. Fundic examination findings included progressive tapetal hyperreflectivity and attenuation of retinal blood vessels. Histologically, the retinas had a selective loss of rod photoreceptors with initial preservation of cone photoreceptors. Retinal degeneration was not accompanied by any other ocular or central nervous system abnormalities, and pedigree analysis suggested an inherited basis for the disease. Mating an affected Wiltshire ram to 2 affected Wiltshire ewes resulted in 6 progeny that all developed retinal degeneration by 2 years of age, while mating of the same affected ram to 6 unaffected ewes resulted in 8 unaffected progeny, consistent with autosomal recessive inheritance. Homozygosity mapping of 5 affected Wiltshire sheep and 1 unaffected Wiltshire sheep using an OvineSNP50 Genotyping BeadChip revealed an identical-by-descent region on chromosome 5, but none of the genes within this region were considered plausible candidate genes. Whole-genome sequencing of 2 affected sheep did not reveal any significant mutations in any of the genes associated with retinitis pigmentosa in humans or progressive retinal atrophy in dogs. Inherited progressive retinal degeneration affecting rod photoreceptors has not been previously reported in sheep, but this disease has several similarities to inherited retinal dystrophies in other species.

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

AAV gene therapies aimed at curing inherited retinal diseases to date have typically focused on photoreceptors and retinal pigmented epithelia within the relatively accessible outer retina. However, therapeutic targeting in diseases such as congenital stationary night blindness (CSNB) that involve defects in ON-bipolar cells (ON-BCs) within the mid-retina has been challenged by the relative inaccessibility of the target cell in intact retinas, the limited transduction efficiency of these cells by existing AAV serotypes, poor availability of established ON-BC-specific promoters, and absence of appropriate patient-relevant large animal models. Here, we demonstrate safe and effective ON-BC targeting by AAV gene therapy in a recently characterized naturally-occurring canine model of CSNB, LRIT3-CSNB. To effectively target ON-BCs, new AAV capsid variants with ON-BC tropism and ON-BC specific modified GRM6 promoters were adopted to ensure cell-specific transgene expression. Notably, subretinal injection of one vector, AAVK9#4-shGRM6-cLRIT3-WPRE, significantly recovered rod-derived b-wave in all treated eyes (6/6) of adult dogs injected at 1-3 years of age. The robust therapeutic effect was evident 7 weeks post-injection and was sustained for at least 1 year in all treated eyes. Scotopic vision was significantly improved in treated eyes based on visually-guided obstacle course navigation. Restoration of LRIT3 signals was confirmed by immunohistochemistry. Thus, we report on the first ON-BC functional rescue in a large animal model using a novel AAV capsid variant and modified promoter construct optimized for ON-BC specificity, thereby establishing both proof-of-concept and a novel translational platform for treatment of CSNB in patients with defects in photoreceptor-to-bipolar signaling.

Laurence Moon Bardet Biedl Syndrome Presenting as Refractory Hyperkalaemia - Explore Everything

Laurence Moon Bardet Biedl syndrome (LMBBS) / Bardet–Biedl disorder (BBS) is an uncommon hereditary disease that is autosomally recessive. It is described by obesity, mental hindrance, dysphoric furthest points (syndactyly, brachydactyly, or polydactyly), retinal dystrophy or retinitis pigmentosa, hypogonadism, and renal abnormalities (among the prevailing aspects).1 LMBBS shares its similarities with Oliver McFarlane syndrome [OMS]. Many patients experienced a gradual loss of vision as a result of retinitis pigmentosa. In retinitis pigmentosa, initially, patients will have night blindness which can be progressed into colour blindness and tunnel vision. Patients of LMBBS may have taurodontism, the condition in which the tooth’s body is greater than the roots.2 Patients of LMBBS can develop chronic renal failure.3 Other features such as brachycephaly, learning disability and gait ataxia can be found in LMBBS patients.

RETINITIS PIGMENTOSA AND ITS AYURVEDIC MANAGEMENT

Retinitis pigmentosa (RP) is a group of diseases involving progressive degeneration of photoreceptor cells of retina. Usually, it starts in mid periphery and advancing towards the macula and fovea centralis. Visual symptoms are nyctalopia (night blindness), tubular vision and reduced visual field. Symptoms of RP mostly starts on early teen age and sever visual loss occurs at ages of 40 to 50 years. RP has worldwide prevalence of 1:3000 to 1:7000 people. Males are more affected than female in ratio of 3:2. Nakulandhya and Shleshmavidagdha Drishti explained under Drishtigata Roga in Ayurvedic literature. These two are described as Sannipataja Syadhi and Kaphaj Vyadhi respectively. They have close resemblance with retinitis pigmentosa in their symptomatology. In current era treatment for RP includes Gene therapy, retinal implants, Neurotrophic factor, stem cells, retinal transplants. But these treatment options are not specific and satisfactory and expensive. All these treatments are still in their early stages of research and development. Ayurvedic Panchakarma therapies and Kriyakalpa therapies can help to regulate vitiated Doshas and provide nourishment and strength to ocular tissue. These therapies can help to maintain the existing vision of patient and reduce progression of RP.

Oguchi's disease: two cases and literature review

Oguchi's disease is a rare form of congenital stationary night blindness, associated with light-dependent golden fundus discoloration. In this report, we describe two cases of Oguchi's disease, both of which had two characteristic features: congenital stationary night blindness and fundoscopic manifestation of the Mizuo–Nakamura phenomenon. In both patients, fundus examination revealed a metallic sheen throughout the retina, which disappeared after 2.5 hours of dark adaptation, suggestive of the Mizuo–Nakamura phenomenon. The characteristic electroretinogram (ERG) changes (i.e., un-recordable rod response and reductions of maximal response, oscillatory potentials, and flicker response) in these patients confirmed the clinical diagnosis of Oguchi's disease. Furthermore, we discuss the results of our literature search for evidence concerning the diagnosis and pathogenesis of this rare disease. Further studies regarding the genes involved in phototransduction and light adaptation are needed to determine the pathogenesis of this rare disease.