Genome wide analysis of enucleated Coats eyes

Abstract

Purpose : Coats disease is an idiopathic, non-hereditary retinal vasculopathy. Clinically it is characterised by retinal telangiectasia accompanied by intraretinal exudation that often progresses to exudative retinal detachment. Patients usually present with unilateral disease and the majority are young males. The Coats phenotype shares some features with familial exudative vitreoretinopathy (FEVR), a Mendelian disorder frequently associated with mutations affecting the norrin-β-catenin signaling pathway. Previously, somatic mutations in NDP, the gene encoding norrin, have been identified in Coats disease but these only account for a small proportion of cases. The purpose of this study was to use whole-exome sequencing (WES) to analyse the DNA of 7 enucleated Coats eyes to discover new genes underlying this disorder

Methods : DNA was extracted from formalin-fixed, paraffin-embedded eyes using the QIAamp DNA FFPE Tissue Kit. WES was performed on the Illumina HiSeq3000 using the Agilent SureSelect capture reagent. Data was aligned using Burrows-Wheeler Aligner (BWA) and variants were processed using Picard and Genome Analysis Toolkit (GATK). A cell based-luciferase reporter assay for β-catenin transcription (TOPflash) was used to determine the pathogenicity of the LRP5 variant.

Results : A novel heterozygous missense mutation in LRP5 was found in one eye, c.2951A>G; p.(Tyr984Cys). The variant is rare and pathogenicity prediction scores suggest that it is deleterious. LRP5 encodes a receptor for the norrin-β-catenin pathway and heterozygous germline mutations cause FEVR. A cell based-luciferase reporter assay for β-catenin transcription (TOPflash) showed that this LRP5 missense variant results in significantly reduced levels of transcription compared to wild-type LRP5 (p= ≤ 0.05).

Conclusions : This is the first report of an LRP5 mutation in Coats disease, providing further evidence that Coats is caused by defects in the norrin-β-catenin pathway and may be a somatic form of FEVR. More detailed analysis of the sequencing data is currently underway to identify mutations in the remaining eyes.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.