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

Expression Profiling Analysis Reveals Key MicroRNA-mRNA Interactions in Early Retinal Degeneration in Retinitis Pigmentosa

Purpose

The aim of this study was to identify differentially expressed microRNAs (miRNAs) that might play an important role in the etiology of retinal degeneration in a genetic mouse model of retinitis pigmentosa (rd10 mice) at initial stages of the disease.

Methods

miRNAs–mRNA interaction networks were generated for analysis of biological pathways involved in retinal degeneration.

Results

Of more than 1900 miRNAs analyzed, we selected 19 miRNAs on the basis of (1) a significant differential expression in rd10 retinas compared with control samples and (2) an inverse expression relationship with predicted mRNA targets involved in biological pathways relevant to retinal biology and/or degeneration. Seven of the selected miRNAs have been associated with retinal dystrophies, whereas, to our knowledge, nine have not been previously linked to any disease.

Conclusions

This study contributes to our understanding of the etiology and progression of retinal degeneration.

RGR variants in different forms of retinal diseases: The undetermined role of truncation mutations

It has been previously reported that mutations in retinal G protein coupled receptor (RGR) are associated with retinitis pigmentosa. The present study aims to systemically analyze the potential role of variants of RGR in retinal diseases. Variants in coding regions and splice sites of RGR were selected from a whole exome sequencing dataset of 820 probands with various forms of genetic ocular diseases. Potential variants of RGR were further confirmed by Sanger sequencing and analyzed in available family members. Clinical data was reviewed for patients with RGR variants. As a result, a total of five variants in RGR were detected in six probands with different types of ocular diseases. Of the five variants, two were novel heterozygous truncation variations, c.266C>A (p.S89*) and c.722_723delCC (p.S241Yfs*29), identified in two probands with high myopia and confirmed by Sanger sequencing. Segregation analysis on available family members demonstrated p.S89* and p.S241Yfs*29 were also present in unaffected relatives. The other three variants of RGR were heterozygous missense variants randomly occurring in patients with different genetic ocular diseases. No homozygous or compound heterozygous variants were detected. The results of the present study suggested that the heterozygous truncation variants in RGR were less likely to be pathogenic. Further studies are expected to evaluate the pathogenicity of variants in RGR.

Gene discovery and prevalence in inherited retinal dystrophies

Inherited retinal dystrophies are Mendelian neurodegenerative conditions classified as pigmentary retinopathies, macular dystrophies and others. Over a 21-year period, from 1990 to 2011, we have screened in Montpellier 107 genes in 609 families and have identified a causal mutation in 68.5% of them. Following a gene candidate approach, we established that RPE65, the isomerohydrolase of the visual cycle, is responsible for severe childhood blindness (Leber congenital amaurosis or early onset retinal dystrophy). In an ongoing study, we screened the genes in a series of 283 families with dominant retinitis pigmentosa and we have estimated that 80% of the families have a mutation in a known gene. A similar study is currently undergoing for autosomal recessive retinitis pigmentosa. Finally, we have identified IMPG1 as a responsible gene for rare cases of macular vitelliform dystrophy with a dominant or recessive inheritance.