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Connexin 26 variants and auditory neuropathy/dys-synchrony among children in schools for the deaf
Xing Cheng1, Li Li, Shanda Brashears
1Department of Genetics, Kresge Hearing Research Laboratory, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA.
Insights
Genetic mutations in connexin 26 (GJB2) and connexin 30 (GJB6) genes cause 12% of nonsyndromic deafness. Some children with GJB2 mutations also show signs of auditory neuropathy/dys-synchrony (AN/AD), indicating outer hair cell function may be preserved.
Area of Science:
- Genetics
- Audiology
- Molecular Biology
Background:
- Nonsyndromic sensorineural deafness is a significant cause of hearing loss in children.
- Connexin 26 (GJB2) and connexin 30 (GJB6) gene mutations are known contributors to hearing impairment.
- Auditory neuropathy/dys-synchrony (AN/AD) is a condition where the auditory nerve does not process sound effectively.
Purpose of the Study:
- To investigate the prevalence of GJB2 and GJB6 gene mutations in children with severe-to-profound hearing loss.
- To explore the relationship between GJB2/GJB6 mutations and the presence of otoacoustic emissions (OAEs), indicative of outer hair cell function.
- To examine potential co-occurrence of GJB2 mutations and auditory neuropathy/dys-synchrony (AN/AD).
Main Methods:
- Genetic analysis of GJB2 and GJB6 genes in 731 children with severe-to-profound hearing loss.
- Otoacoustic emissions (OAEs) testing to assess outer hair cell function in children with hearing loss.
- Genotyping of children with confirmed OAEs and identified GJB2 mutations.
Main Results:
- Mutations in GJB2 and GJB6 genes were identified in at least 12% of children with nonsyndromic sensorineural deafness.
- 76 children with hearing loss had detectable OAEs, suggesting potential AN/AD.
- Five children with OAEs were found to have specific GJB2 mutations, including one with confirmed unilateral AN/AD and a GJB2 genotype of 35delG/V95M.
Conclusions:
- GJB2 and GJB6 gene mutations are a significant cause of nonsyndromic deafness in the studied population.
- The presence of OAEs in individuals with GJB2 mutations suggests that gap junction dysfunction does not always abolish outer hair cell function.
- GJB2 mutations may coexist with auditory neuropathy/dys-synchrony, highlighting the complexity of hearing loss etiologies.
Abstract:
Genetic and auditory studies of 731 children with severe-to-profound hearing loss in US schools for the deaf and 46 additional children receiving clinical services for hearing loss ranging from moderate to profound demonstrated that mutations in the connexin 26 (GJB2) and connexin 30 (GJB6) genes explain at least 12% of those with nonsyndromic sensorineural deafness. Otoacoustic emissions (OAEs) testing to detect functional outer hair cells indicated that 76 of the children had emissions and therefore may have (as yet unconfirmed) auditory neuropathy/dys-synchrony (AN/AD). Five of these children with OAEs were GJB2 homozygotes or compound heterozygotes with the genotypes 35delG/35delG, W77X/W77X, 35delG/360delGAG, 35delG/V95M, and V84M/M34T. In particular, unilateral AN/AD was confirmed in a child with moderate hearing loss and the 35delG/V95M genotype. Detecting OAEs in individuals with GJB2 mutations suggests that lack of functional gap junctions as a result of GJB2 mutations does not necessarily destroy all outer hair cell function.
