Whole exome sequencing identifies mutations in Usher syndrome genes in profoundly deaf Tunisian patients

PLoS One. 2015 Mar 23;10(3):e0120584. doi: 10.1371/journal.pone.0120584. eCollection 2015.

Abstract

Usher syndrome (USH) is an autosomal recessive disorder characterized by combined deafness-blindness. It accounts for about 50% of all hereditary deafness blindness cases. Three clinical subtypes (USH1, USH2, and USH3) are described, of which USH1 is the most severe form, characterized by congenital profound deafness, constant vestibular dysfunction, and a prepubertal onset of retinitis pigmentosa. We performed whole exome sequencing in four unrelated Tunisian patients affected by apparently isolated, congenital profound deafness, with reportedly normal ocular fundus examination. Four biallelic mutations were identified in two USH1 genes: a splice acceptor site mutation, c.2283-1G>T, and a novel missense mutation, c.5434G>A (p.Glu1812Lys), in MYO7A, and two previously unreported mutations in USH1G, i.e. a frameshift mutation, c.1195_1196delAG (p.Leu399Alafs*24), and a nonsense mutation, c.52A>T (p.Lys18*). Another ophthalmological examination including optical coherence tomography actually showed the presence of retinitis pigmentosa in all the patients. Our findings provide evidence that USH is under-diagnosed in Tunisian deaf patients. Yet, early diagnosis of USH is of utmost importance because these patients should undergo cochlear implant surgery in early childhood, in anticipation of the visual loss.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Connexin 26
  • Connexins / genetics
  • Deafness / genetics*
  • Exome*
  • Family
  • Female
  • Genome-Wide Association Study*
  • Genotype
  • High-Throughput Nucleotide Sequencing*
  • Humans
  • Male
  • Mutation*
  • Myosins / genetics
  • Pedigree
  • Phenotype
  • Retina / metabolism
  • Retina / pathology
  • Tunisia

Substances

  • Connexins
  • Connexin 26
  • Myosins

Grant support

This work was supported by the Tunisian Ministry of Public Health, the Ministry of Higher Education and Scientific Research (LR11IPT05), the E.C. Grant agreement N° 295097 for FP7 project GM-NCD-Inco (www.genomedika.org), ZR is recipient of a Mobidoc Fellowship under the Programme d’Appui au Système de recherche et d’Innovation (PASRI-Europe Aid) and BNP Paribas foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.