CONNEXIN 26/GJB2 RELATED HEREDITARY HEARING LOSS
GJB2 Sequencing
DNA ANALYSIS
Also see: 6355 - GJB6-Related DFNB1 Hereditary Hearing Loss

Hereditary hearing loss (HHL) is caused by mutations in different genes, and can be inherited as an autosomal dominant, autosomal recessive, X-linked, or mitochondrial condition. Mutations in the GJB2 gene, which encodes the connexin 26 protein, are the most frequent cause of autosomal recessive nonsyndromic hereditary hearing loss (NSHHL). Different mutations in GJB2 have also been associated with autosomal dominant NSHHL, and in syndromic hereditary hearing loss associated with skin disorders. The connexin 26 protein appears to participate in potassium recycling in the endolymph in the inner ear. Mutations in the GJB2 gene are found in various populations, with a carrier rate of approximately 2.5-3% of the United States Caucasian population, and ~4.5-5% of the Ashkenazi Jewish population. More than 50 GJB2 mutations associated with hearing loss have been identified. Diagnostic sequence analysis of the GJB2 coding region is available to hearing impaired patients in whom a genetic etiology of hearing loss is suspected.

Reasons for Referral:

Confirmation of diagnosis of hereditary hearing loss
Carrier detection in family members at risk for a known GJB2 mutation

Testing Methodology:

Amplification of the GJB2 gene coding region is performed by PCR on patient genomic DNA. Bi-directional DNA sequence analysis is performed on PCR products using automated, fluorescent dideoxy sequencing methods.

Sensitivity:

>99% Detection

Specimen Requirements:

Blood: EDTA (purple-top) tubes: Adults: 14 cc; Child: 6 cc; Infant: 2-3 cc
Requisition and consent forms required. Please contact the laboratory for more detailed information.

Turnaround Time:

4 weeks

References:

1. Cohn, et al. (1999) Pediatrics 103: 546-550.
2. Cohn, et al. (1999) Am. J. Med. Genet. 89: 130-136.
3. Morell, et al. (1998) N. Engl. J. Med. 339: 1500-1505.
4. Sundstrom, et al (1999) Am. J. Med. Genet. 89: 123-129.

CPT Codes and Prices:

Index: 83904X3, 83912, 83909X6, 83898, 83894, 83891
Known Familial Mutation: 83904x2, 83912, 83909x2, 83898, 83891, 83894