Connexin26 mutations associated with nonsyndromic hearing loss

Objective: Mutations in the GJB2 gene are a major cause of autosomal recess ive and sporadic types of congenital deafness. The 35delG mutation is the m ost frequent type of mutation in white populations. However, several other forms were reported, such as 167delT among Ashkenazi Jews and R143W in Afri cans. The present study investigated the mutations of connexin26 (Cx26) fou nd in patients with nonsyndromic hearing loss (NSHL) and newborns in the Ko rean population. Study Design: The sequencing data for 147 unrelated patien ts with congenital NSHL and 100 audiologically screened newborns were inclu ded in this prospective study. Methods: Genomic DNA samples from all patien ts and newborns were sequenced in both directions for detection of Cx26 mut ations. Results: Thirteen different types of mutations were found in the pa tients and newborns. V271 and E114G are the popular types of polymorphic mu tations in both groups. 235delC-deletion and frame-shift was detected in pa tients (15 in 294 alleles) and newborns (1 in 200 alleles). 35delG was rare ly found in both group. In addition to above mutations, several types of mu tations-S85P, K41R, S72C, V84A, 176-191del, and 299-300del-were identified. The family study of the 235delC showed a typical autosomal recessive trait of NSHL in their audiological evaluation of hearing threshold. Conclusion: The frequency of 235delC allele showed much higher in the patients (5%) th an in newborns (0.5%). We rarely found 35delC mutant in both groups. These results suggest that the different types of Cx26 mutations affect autosomal recessive NSHL according to ethnic background.