Targeted Exome Sequencing Identified a Novel USH2A Mutation in a Chinese Usher Syndrome Family

Abstract

Background To identify the gene mutation in a Chinese family with Usher syndrome type 2 and describe the clinical features. Methods A 23-year-old man complain of 10-year nyctalopia and a 3-year decline in visual acuity in both eyes accompanied by congenital dysaudia. To clarify the diagnosis, the clinical symptoms of the patient were observed and analysed in combination with comprehensive ophthalmologic examinations as well as genetic analysis(Targeted exome sequencing, TES). Results Typical clinical presentation of Usher syndrome on fundus features was found, which included a wax yellow-like disc, bone-spicule formations, and retinal vessel stenosis. Optical coherence tomography(OCT) and optical coherence tomography angiography (OCTA) showed loss of the ellipsoid zone and a reduction in paracaval vessel density in both eyes. Genetic analysis identified the presence of novel homozygote of c.8483_8486del (p.S2828fs) in USH2A, a gene responsible for Usher syndrome type 2 (OMIM:276901). This novel mutation in USH2A led to premature translation termination, resulting in the deletion of 19 fibronectin type 3 domains(FN3), which plays an important role in protein binding. Based on the clinical manifestations and genetic result, the patient was diagnosed with Usher syndrome type 2. Conclusions We found a novel mutation of c.8483_8486del in USH2A gene through TES techniques for 381 inherited retinal disease (IRD) related genes. The results of this study broaden the spectrum of mutations in Usher syndrome type 2 and suggest that the combination of TES molecular diagnosis and clinical information can help USH patients obtain a better diagnoses.