Yasmin Tatour 1 , Jonathan Tamaiev 1 , Shamaly Shamaly 2 , Roberto Colombo 3 , 4 , Ephrat Bril 5 , Tom Rabinowitz 6 , Alona Yaakobi 7 , Eedy Mezer 1 , 8 , Rina Leibu 8 , Beatrice Tiosano 1 , 7 , Noam Shomron 6 , Itay Chowers 5 , Eyal Banin 5 , Dror Sharon 5 , Tamar Ben-Yosef , 1
22 February 2019
To identify the genetic basis for retinitis pigmentosa (RP) in a cohort of Jewish patients from Caucasia.
Patients underwent a detailed ophthalmic evaluation, including funduscopic examination, visual field testing, optical coherence tomography (OCT), and electrophysiological tests, electroretinography (ERG) and visual evoked potentials (VEP). Genetic analysis was performed with a combination of whole exome sequencing (WES) and Sanger sequencing. Bioinformatic analysis of the WES results was performed via a customized pipeline. Pathogenicity of the identified intronic variant was evaluated in silico using the web tool Human Splicing Finder, and in vitro, using a minigene-based splicing assay. Linkage disequilibrium (LD) analysis was used to demonstrate a founder effect, and the decay of LD over generations around the mutation in Caucasus Jewish chromosomes was modeled to estimate the age of the most recent common ancestor.
In eight patients with RP from six unrelated families, all of Caucasus Jewish ancestry, we identified a novel homozygous intronic variant, located at position −9 of PDE6B intron 15. The c.1921–9C>G variant was predicted to generate a novel acceptor splice site, nine bases upstream of the original splice site of intron 15. In vitro splicing assay demonstrated that this novel acceptor splice site is used instead of the wild-type site, leading to an 8-bp insertion into exon 16, which is predicted to cause a frameshift. The presence of a common ancestral haplotype in mutation-bearing chromosomes was compatible with a founder effect.