[Mutations of GJB2 gene in infants with non-syndromic hearing impairment]

To explore the relationship between GJB2 gene mutations and severe-to-profound bilateral non-syndromic hearing impairment (NSHI).

Peripheral blood was collected from 20 infants with severe-to-profound bilateral NSHI confirmed by otoacoustic emissions (OAE), auditory brainstem responses (ABR) and clinical physical examination, 11 male and 9 female, aged 3 months to 3 years. PCR and sequencing technique were used to analyze the coding region of GJB2 gene. Fifty persons with normal hearing, 25 males and 25 female, aged 20 approximately 50, all without family history of hearing impairment, were used as controls.

Three infants (15%) were identified as 235delC/235delC homozygotes; one infant was identified as 235delC/299-300delAT compound heterozygote; one was identified as 235delC heterozygote; and one as 235delC/605ins46 compound heterozygote with 605ins46 mutation, a novel mutation reported in Chinese for the first time. GJB2 gene mutations were found in 5 NSHI infants (25%). The allelic frequency of 235delC allele was 22.5% in the NSHI infants and 1% in the control group (P < 0.01). Besides, multiple polymorphisms such as V27I, V37I, E114G, T123N were found in both the patients and controls.

GJB2 analysis is an important test for infants with severe-to-profound bilateral NSHI. 235delC is the main pathogenic mutation site in GJB2 gene.