The GJB2 and GJB6 genes provide instructions for making proteins called gap junction betas or connexins. Connexin proteins form channels called gap junctions that permit the transport of nutrients, charged atoms, and signaling molecules between neighboring cells that are in contact with each other. Gap junctions made with connexin 26 and connexin 30 transports potassium ions and certain small molecules.
Connexin 26 and connexin 30 are found in cells throughout the body, including the inner ear, and the skin. Hearing requires the conversion of sound waves to electrical nerve impulses. This conversion involves many processes, including maintaining the proper level of potassium ions in the inner ear. Some studies indicate that channels made with connexin proteins help to maintain the correct level of potassium ions. Other research suggests that connexins are required for the maturation of certain cells in the cochlea.
Deafness, Autosomal Dominant 3A; DFNA3A
Deafness, Autosomal Recessive 1A; DFNB1A
Nonsyndromic neurosensory deafness, hearing loss can occur between ages 10-20.
Hearing loss, sensorineural, prelingual profound, vestibular dysfunction (in some patients)
|Deafness, Autosomal Dominant 3B; DFNA3B
Deafness, Autosomal Recessive 1B, DFNB1B
Childhood-onset, progressive, moderate-to-severe high-frequency sensorineural hearing impairment. Affected individuals have no other associated medical findings.
The CX30 deletion accounts for a small portion of DFNB1 hearing loss. It has been found in a higher percentage of individuals having a single CX26 mutation.
Methodology: Sequencing of entire coding region
Purpose: Confirmation of Clinical Diagnosis, identify a second mutation in patients who carry a single CX26 mutation.
ICD-10 Code H90.5
Test Requisition: Sequencing Requisition
GJB2 CPT Code: 81252 Cost: $440.00
GJB6 CPT Code: 81254 Cost: $396.00
Panel CPT Codes: 81252, 81254 Cost: $836.00
Turn-around-time: 3-4 weeks
1. Denoyelle, F., Lina-Granade, G., Plauchu, H., Bruzzone, R., Chaib, H. et al. (1998) “Connexin 26 gene linked to a dominant deafness”. Nature 393: 319-320.
2. Grifa, A., Wagner, C. A., D'Ambrosio, L., Melchionda, S., Bernardi, F. et al. (1999) “Mutations in GJB6 cause nonsyndromic autosomal dominant deafness at DFNA3 locus”. Nature Genet. 23: 16-18.