title: GJB2 mutations in the Swiss hearing impaired.
abstract: OBJECTIVE
  Mutations in the GJB2 gene encoding connexin 26 (Cx26) protein are a major cause for nonsyndromic autosomal recessive and sporadic deafness. However, its contribution to hearing impairment in Switzerland remains undefined. To determine the frequency and type of GJB2 mutations in the Swiss hearing-impaired population diagnosed under the age of 2 yr and at 2 yr and older and to assess the effectiveness of denaturing high-performance liquid chromatography (DHPLC) in screening for mutation in GJB2.
  
  
  METHODS
  Thirty-four patients with hearing impairment underwent mutation screening of the single coding exon of GJB2 with DHPLC followed by bidirectional sequencing to identify sequence alterations.
  
  
  RESULTS
  GJB2 mutations were more common in children diagnosed with hearing impairment under the age of 2 yr compared to the group 2 yr and older. In patients under age 2 yr, 9 of 20 (45%) harbored 13 GJB2 mutations including a common 313del14nt mutation; four of these patients were homozygous or compound heterozygous for GJB2 mutations. In contrast, 2 of 14 patients in the 2 yr and older group (14%) had a single mutation in GJB2. The 35delG mutation was exclusively found in 5 patients under the age of 2 yr. DHPLC for mutation screening was 100% sensitive and 83% specific for detecting sequence alterations in GJB2.
  
  
  CONCLUSIONS
  In Switzerland, GJB2 mutations are a major cause of nonsyndromic hearing impairment in children under the age of 2. Similar to other populations, GJB2 mutations are uncommon in the affected Swiss patients identified after 2 yr. Although 35delG mutation is common in the hearing-impaired children under the age of 2, it was absent in patients diagnosed with hearing impairment after the age of 2. DHPLC is a highly sensitive tool for detection of GJB2 mutations.
authors.affiliation: Laboratory of Molecular Otology, Epstein Laboratories, Department of Otolaryngology-Head and Neck Surgery, University of California San Francisco, USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gürtler
authors.forename: Yuil
authors.initials: Y
authors.lastname: Kim
authors.forename: Anand
authors.initials: A
authors.lastname: Mhatre
authors.forename: René
authors.initials: R
authors.lastname: Müller
authors.forename: Rudolf
authors.initials: R
authors.lastname: Probst
authors.forename: Anil K
authors.initials: AK
authors.lastname: Lalwani
mesh_terms: D000367:Age Factors; D001309:Auditory Threshold; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003001:Cloning, Molecular; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods; D005260:Female; D005820:Genetic Testing / Q000379:methods; D034381:Hearing Loss / Q000453:epidemiology* / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009691:Nucleic Acid Denaturation; D010641:Phenotype; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013557:Switzerland / Q000453:epidemiology
chemical_list: D017630:Connexins; C000607042:GJB2 protein, human; D000072259:Connexin 26