Chicago Center for Jewish Genetics Disorders - Ashkenazi Disorders: Non-Syndromic Hearing Loss

Ashkenazi Disorders: Mendelian

Gene: Connexin-26 hearing loss is caused by mutations in the GJB2 gene, which is located at 13q11-12. GJB2 encodes for the protein connexin-26 (Cx26). Connexin-26 hearing loss is also called DFNB1.

Mutations and testing: Two mutations account for the vast majority of cases of DFNB1 hearing loss seen in the Ashkenazi Jewish population. These are 35delG (30delG), which is seen in ~15% of Ashkenazi Jewish patients, and 167delT, which is seen in ~85% of Ashkenazi Jewish patients. Within the Ashkenazi Jewish population, the 167delT mutation carrier frequency is approximately 4% and the 35delG mutation carrier frequency is approximately .8%.

Traits: DFNB1 hearing loss is caused by mutations in the connexin-26 gene, which is a beta-2 gap junction protein. A cluster of these beta-2 gap junction proteins acts as a channel for exchange of ions and molecules between cells in the cochlea. This channel may allow for a rapid propagation of electrical signals and synchronization of activity in excitable tissue, such as the hair cells in the inner ear. DFNB1 hearing loss is characterized by severe or severe-to-profound hearing loss without any other related signs. The hearing loss is present at birth and is non-progressive. It can occasionally be mild, moderate, or moderate-to-severe, and can vary, even within a family. Vestibular function is normal.

Treatment: After assessment of hearing loss, hearing aids or cochlear implants may be considered.

Nonsyndromic Hereditary Hearing Loss and Deafness, Connexin 26 (DFNB1) from Geneclinics.org
http://www.genetests.org/profiles/dfnb1

Reviewed by Dr. Joel Charrow, Children's Memorial Hospital.
1/03

<< Back

This page last updated on January 10, 2003.