Early-onset, severe retinal dystrophy caused by mutations in the gene encoding reti- nal pigment epithelium-specific 65-kDa protein (RPE65) is associated with poor vi- sion at birth and complete loss of vision in early adulthood. We administered to three young adult patients subretinal injections of recombinant adeno-associated virus vector 2/2 expressing RPE65 complementary DNA (cDNA) under the control of a human RPE65 promoter. There were no serious adverse events. There was no clinically significant change in visual acuity or in peripheral visual fields on Gold- mann perimetry in any of the three patients. We detected no change in retinal re- sponses on electroretinography. One patient had significant improvement in visual function on microperimetry and on dark-adapted perimetry. This patient also showed improvement in a subjective test of visual mobility. These findings provide support for further clinical studies of this experimental approach in other patients with mutant RPE65. (ClinicalTrials.gov number, NCT00643747.)

/pdf/effect-of-gene-therapy-on-visual-function-in-leber-s-5gbkan2vhy.pdf

Effect of gene therapy on visual function in Leber's congenital amaurosis.

Leber congenital amaurosis: genes, proteins and disease mechanisms.

Leber congenital amaurosis (LCA) is one of the main causes of childhood blindness. To date, mutations in eight genes have been described, which together account for ∼45% of LCA cases. We localized the genetic defect in a consanguineous LCA-affected family from Quebec and identified a splice defect in a gene encoding a centrosomal protein (CEP290). The defect is caused by an intronic mutation (c.2991+1655A→G) that creates a strong splice-donor site and inserts a cryptic exon in the CEP290 messenger RNA. This mutation was detected in 16 (21%) of 76 unrelated patients with LCA, either homozygously or in combination with a second deleterious mutation on the other allele. CEP290 mutations therefore represent one of the most frequent causes of LCA identified so far.

Mutations in the CEP290 (NPHP6) Gene Are a Frequent Cause of Leber Congenital Amaurosis

Retinal pigment epithelial cells (RPE) constitute a simple layer of cuboidal cells that are strategically situated behind the photoreceptor (PR) cells. The inconspicuousness of this monolayer contrasts sharply with its importance [1]. The relationship between the RPE and PR cells is crucial to sight; this is evident from basic and clinical studies demonstrating that primary dysfunctioning of the RPE can result in visual cell death and blindness. RPE cells carry out many functions including the conversion and storage of retinoid, the phagocytosis of shed PR outer segment membrane, the absorption of scattered light, ion and fluid transport and RPE-PR apposition. The magnitude of the demands imposed on this single layer of cells in order to execute these tasks, will become apparent to the reader of this review as will the number of clinical disorders that take origin from these cells.

/pdf/the-retinal-pigment-epithelium-in-health-and-disease-lqofq6e2p6.pdf

The Retinal Pigment Epithelium in Health and Disease

https://repository.upenn.edu/cgi/viewcontent.cgi?article=1115&context=vet_papers

Long-Term Restoration of Rod and Cone Vision by Single Dose rAAV-Mediated Gene Transfer to the Retina in a Canine Model of Childhood Blindness

Leber congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies, responsible for congenital blindness. Disease-associated mutations have been hitherto reported in seven genes. These genes are all expressed preferentially in the photoreceptor cells or the retinal pigment epithelium but they are involved in strikingly different physiologic pathways resulting in an unforeseeable physiopathologic variety. This wide genetic and physiologic heterogeneity that could largely increase in the coming years, hinders the molecular diagnosis in LCA patients. The genotyping is, however, required to establish genetically defined subgroups of patients ready for therapy. Here, we report a comprehensive mutational analysis of the all known genes in 179 unrelated LCA patients, including 52 familial and 127 sporadic (27/127 consanguineous) cases. Mutations were identified in 47.5% patients. GUCY2D appeared to account for most LCA cases of our series (21.2%), followed by CRB1 (10%), RPE65 (6.1%), RPGRIP1 (4.5%), AIPL1 (3.4%), TULP1 (1.7%), and CRX (0.6%). The clinical history of all patients with mutations was carefully revisited to search for phenotype variations. Sound genotype-phenotype correlations were found that allowed us to divide patients into two main groups. The first one includes patients whose symptoms fit the traditional definition of LCA, i.e., congenital or very early cone-rod dystrophy, while the second group gathers patients affected with severe yet progressive rod-cone dystrophy. Besides, objective ophthalmologic data allowed us to subdivide each group into two subtypes. Based on these findings, we have drawn decisional flowcharts directing the molecular analysis of LCA genes in a given case. These flowcharts will hopefully lighten the heavy task of genotyping new patients but only if one has access to the most precise clinical history since birth.

/pdf/leber-congenital-amaurosis-comprehensive-survey-of-the-1lcixdntke.pdf

Leber congenital amaurosis: comprehensive survey of the genetic heterogeneity, refinement of the clinical definition, and genotype-phenotype correlations as a strategy for molecular diagnosis.

Louisa Santos

Papers

Leber congenital amaurosis: comprehensive survey of the genetic heterogeneity, refinement of the clinical definition, and genotype-phenotype correlations as a strategy for molecular diagnosis.