Autosomal Recessive Retinitis Research Articles

Clinical and Genetic Correlations of Inherital Retinal Disease with Mutations in the ABCA4 Gene by Patients of the Russian Population

Aim: to study genotype-phenotype correlations in patients with inherited retinal diseases with mutations in ABCA4 gene in Russian Federation.Patients and methods. 21 patients from Russian population aged from 7 to 51 years old (mean age 20 ± 11 years with best-corrected visual acuity from 0,02 to 0,6 (0,14 ± 0,11) with ABCA4-associated retinopathy, verified by molecular genetics methods. All patients besides standard ophthalmic examination and photodocumentation were performed Spectral-Domain OCT and fundus autofluorescence on Spectralis ®HRA+OCT (Heidelberg Engineering, Germany). Full-field electroretinogram (ERG), 30-Hz flicker ERG and macular chromatic ERG (MERG) to red stimulus were recorded on electroretinographic system MBN (MBN, Russia). (Russia) Molecular genetic studies were performed using Next Generation Sequencing (NGS) and Sandger direct sequencing. Results: In ABCA4-associated Stargardt disease 1 type (STGD1) genotype [p.L541P, p.A1038V] of «frequent» mutations was revealed in 9 patients, in 2 cases in was associated another “frequent” mutation p.G1961E. In 4 patients with genotype [p.L541P, p.A1038V] “severe” phenotype of Stargardt disease was found: with large defect of the ellipsoid zone and large zone of central reduced autofluorescence, severely subnormal macular ERG (MERG) to red stimulus and subnormal 30 Hz flicker and full-field maximal ERG. In one patient with these mutations in homozygous state ABCA4-associated cone-rod dystrophy (CORD3, clinically looking alike secondary retinal dystrophy is diagnosed. In 2 patients with genotype [p.L541P, p.A1038V] and mutation p.G1961E was found mild phenotype. One patient with homozygous mutation p.R653C autosomal recessive ABCA4-associated retinitis pigmentosa (RP19) was diagnosed. Clinical picture and autofluorescence were polymorphic in all patients.Conclusions. Our study with ophthalmological, molecular genetics and instrumental methods widens the spectrum of clinical signs of inherited eye diseases associated with mutations in АВСА4 gene, widens the spectrum mutations in Russian Federation and reveals clinicо-genetic genotype-phenotype correlations.

Genetic Rescue Reverses Microglial Activation in Preclinical Models of Retinitis Pigmentosa.

Microglia cells (MGCs) play a key role in scavenging pathogens and phagocytosing cellular debris in the central nervous system and retina. Their activation, however, contributes to the progression of multiple degenerative diseases. Given the potential damage created by MGCs, it is important to better understand their mechanism of activation. Here, we explored the role of MGCs in the context of retinitis pigmentosa (RP) by using four independent preclinical mouse models. For therapeutic modeling, tamoxifen-inducible CreER was introduced to explore changes in MGCs when RP progression halted. The phenotypes of the MGCs were observed using live optical coherence tomography, live autofluorescence, and immunohistochemistry. We found that, regardless of genetic background, MGCs were activated in neurodegenerative conditions and migrated beyond the layers where they are typically found to the inner and outer segments, where degeneration was ongoing. Genetic rescue not only halted degeneration but also deactivated MGCs, regardless of whether the intervention occurred at the early, middle, or late stage of the disease. These findings suggest that halting long-term disease progression may be more successful by downregulating MGC activity while co-administering the therapeutic intervention.

Restoration of Vision in the pde6β-deficient Dog, a Large Animal Model of Rod-cone Dystrophy

Defects in the β subunit of rod cGMP phosphodiesterase 6 (PDE6β) are associated with autosomal recessive retinitis pigmentosa (RP), a childhood blinding disease with early retinal degeneration and vision loss. To date, there is no treatment for this pathology. The aim of this preclinical study was to test recombinant adeno-associated virus (AAV)-mediated gene addition therapy in the rod-cone dysplasia type 1 (rcd1) dog, a large animal model of naturally occurring PDE6β deficiency that strongly resembles the human pathology. A total of eight rcd1 dogs were injected subretinally with AAV2/5RK.cpde6β (n = 4) or AAV2/8RK.cpde6β (n = 4). In vivo and post-mortem morphological analysis showed a significant preservation of the retinal structure in transduced areas of both AAV2/5RK.cpde6β- and AAV2/8RK.cpde6β-treated retinas. Moreover, substantial rod-derived electroretinography (ERG) signals were recorded as soon as 1 month postinjection (35% of normal eyes) and remained stable for at least 18 months (the duration of the study) in treated eyes. Rod-responses were undetectable in untreated contralateral eyes. Most importantly, dim-light vision was restored in all treated rcd1 dogs. These results demonstrate for the first time that gene therapy effectively restores long-term retinal function and vision in a large animal model of autosomal recessive rod-cone dystrophy, and provide great promise for human treatment.

Mutations in C8orf37, Encoding a Ciliary Protein, are Associated with Autosomal-Recessive Retinal Dystrophies with Early Macular Involvement

Cone-rod dystrophy (CRD) and retinitis pigmentosa (RP) are clinically and genetically overlapping heterogeneous retinal dystrophies. By using homozygosity mapping in an individual with autosomal-recessive (ar) RP from a consanguineous family, we identified three sizeable homozygous regions, together encompassing 46 Mb. Next-generation sequencing of all exons, flanking intron sequences, microRNAs, and other highly conserved genomic elements in these three regions revealed a homozygous nonsense mutation (c.497T>A [p.Leu166(∗)]) in C8orf37, located on chromosome 8q22.1. This mutation was not present in 150 ethnically matched control individuals, single-nucleotide polymorphism databases, or the 1000 Genomes database. Immunohistochemical studies revealed C8orf37 localization at the base of the primary cilium of human retinal pigment epithelium cells and at the base of connecting cilia of mouse photoreceptors. C8orf37 sequence analysis of individuals who had retinal dystrophy and carried conspicuously large homozygous regions encompassing C8orf37 revealed a homozygous splice-site mutation (c.156-2A>G) in two siblings of a consanguineous family and homozygous missense mutations (c.529C>T [p.Arg177Trp]; c.545A>G [p.Gln182Arg]) in siblings of two other consanguineous families. The missense mutations affect highly conserved amino acids, and in silico analyses predicted that both variants are probably pathogenic. Clinical assessment revealed CRD in four individuals and RP with early macular involvement in two individuals. The two CRD siblings with the c.156-2A>G mutation also showed unilateral postaxial polydactyly. These results underline the importance of disrupted ciliary processes in the pathogenesis of retinal dystrophies.

Screening genes of the visual cycle RGR, RBP1 and RBP3 identifies rare sequence variations

The visual cycle is essential for vision and several genes encoding proteins of the cycle have been found mutated in various forms of inherited retinal dystrophy. We screened 3 genes of the visual cycle. RGR, encoding the retinal pigment epithelium (RPE) G protein-coupled receptor acting in vitro as a photoisomerase; RBP1, encoding the ubiquitous cellular retinol binding protein carrying intracellular all-trans retinoids; RBP3, encoding the interphotoreceptor retinoid binding protein, a retinal-specific protein which shuttles all-trans retinol from photoreceptors to RPE and 11-cis retinal from RPE to photoreceptors. We used denaturing high performance liquid chromatography (D-HPLC) and direct sequencing to screen 216 patients (134 with autosomal recessive or sporadic retinitis pigmentosa (RP) and 82 with other retinal dystrophies) for RBP1 and RBP3, and 331 patients for RGR (79 cases with autosomal dominant RP and 36 RP cases with undetermined inheritance were added to the 216 previous patients). Several variants were found in the 3 genes, including unique amino acid changes, but none of them showed evidence of pathogenicity. It is likely that mutations in RGR, RBP3, and possibly RBP1 occur rarely in inherited retinal dystrophies.

515. Mutation Independent Knockdown of Mutant mRNA by RNA Interference and Replacement by mRNA with Knockdown-Resistant Codons

Purpose: Many dominant disorders present with a very heterogeneous mutation spectrum. Hence, it would be ideal to develop therapies that are mutation independent. RNA interference (RNAi) is a potentially powerful tool for the treatment of dominant diseases. More than 100 different mutations in the gene encoding rhodopsin cause a wide variety of diseases including autosomal dominant and recessive retinitis pigmentosa (RP), congenital stationary night blindness and retinitis punctata albescens. The purpose of this study was to explore the potential of RNAi to ameliorate dominant disease associated with mutations in rhodopsin.

Posterior column ataxia and retinitis pigmentosa: a distinct clinical and genetic disorder.

Autosomal recessive posterior column ataxia and retinitis pigmentosa (PCARP) is a movement disorder that was genetically mapped to a disease locus (AXPC1) on chromosome 1q32-q31 in an inbred population of Dutch-German ancestry in the continental United States. We performed genetic linkage analysis and haplotype reconstruction on a different family from Spain with an identical phenotype to determine if the neurologic signs of an early-onset ataxia, retinitis pigmentosa, and a sensory neuropathy also mapped to the AXPC1 locus. The disease phenotype was linked in the candidate interval with a maximum lod score of 3.56 at a recombination fraction of 0.0 for locus D1S414. Haplotypes were discordant and suggested that the disease mutation arose independently from at least two populations. These results refine the classification of early-onset ataxia, abrogate a founder effect for this recessive disorder, and provide evidence that PCARP is a distinct, homogeneous, clinical, and genetic disorder.

Introduction

Introduction

Analysis of the DNA of patients with retinitis pigmentosa with a cellular retinaldehyde binding protein cDNA

We used a cDNA fragment corresponding to the human cellular retinaldehyde binding protein (CRALBP) gene to search for mutations at this locus in patients with autosomal dominant, autosomal recessive, or isolate retinitis pigmentosa, and Usher's syndrome, type I. No gene deletions or rearrangements could be detected in any patient by Southern blotting. We identified a Pvu II restriction fragment length polymorphism (RFLP) defining two alleles at the CRALBP locus in the normal population. We used this RFLP to analyze the genomic DNA of large sets of unrelated patients with autosomal dominant, autosomal recessive, or isolate retinitis pigmentosa. Within each of these groups, RFLP alleles at the CRALBP locus showed no linkage disequilibrium (departure from Hardy-Weinberg equilibrium). In addition, two autosomal dominant, two autosomal recessive, and three Usher's syndrome, type I pedigrees each showed no cosegregation of the CRALBP locus and the disease locus. We could find no evidence that mutations of the CRALBP gene are associated with the common forms of retinitis pigmentosa or Usher's syndrome, type I.