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Hearing Loss, Non-Syndromic (GJB2 and GJB6)

Alternate test name

Non-Syndromic Hearing Loss (Connexin 26)

Gene name / Alternate gene name
  • GJB2 & GJB6
  • CX26, CX30
Gap junction protein, beta 2; Connexin 26 Gap junction protein, beta 6; Connexin 30
Lab area
Genome Diagnostics - Molecular Genetics
Method and equipment
GJB6 Deletion/duplication analysis via MLPA; GJB2 Sequencing
Expected turn-around time
Pregnancy/STAT: 2-3 weeks Routine: 4-6 weeks
Specimen type

Blood; extracted DNA is not accepted for GJB6 Deletion/Duplication Analysis.

If sending a prenatal sample, please contact the laboratory prior to sending sample to discuss sample requirements.

For details about specimen requirements, please refer to: Specimen Type & Requirements (PDF).

Specimen requirements
  • Blood: 5-10 mL in EDTA, 0.5 mL in EDTA (neonate); 
  • DNA-minimum 10 ug in 100 uL low TE (pH8.0)
Storage and transportation

Room Temperature

For details about specimen requirements, please refer to: Specimen Type and Requirements

DNA extracted at an external lab is not accepted for MLPA testing.

Special requirements

Special Instructions for Genome Diagnostics Samples

If sample shipment >48 hours, ship on ice.

Shipping information
The Hospital for Sick Children
Division of Genome Diagnostics
555 University Avenue, Black Wing, Room 3416
Toronto, ON
M5G 1X8
Phone: 416-813-7200 ext. 2
Hours: Monday to Friday, 8 a.m. to 4:30 p.m.
Off hours: Please send to Rapid Response Laboratory, 555 University Avenue, Room 3642
Email Molecular Lab:
Email Cytogenetics:
Background and clinical significance

Non-syndromic sensorineural hearing loss (NSHL) is a common disability affecting approximately 1 in 1000 newborns. In approximately 50% of children with congenital deafness the hearing loss is due to inherited causes. The most common form of inherited hearing loss is autosomal recessive non-syndromic hearing loss (AR-NSHL), which affects approximately 1 in every 2500 children.

Many different genes have been shown to play a role in NSHL.Mutations in the in the GJB2 gene have been implicated in 50 to 80% of AR-NSHL cases, making this the most common cause of AR-NSHL. The GJB2 gene encodes a gap junction protein called connexin 26, which is important in the development of the inner ear. A second gap junction protein, connexin 30 encoded by the GJB6 gene, can also cause AR-NSHL. In particular a recurrent deletion in the GJB6 gene (delGJB6-D13S1830) has been reported to cause AR-NSHL in approximately 20% of patients who also have one GJB2 gene mutation.

The strategy used for testing for non-syndromic hearing loss is complete sequencing of the coding region and flanking exon/intron boundaries of the GJB2 gene, and direct mutation testing for the recurrent deletion mutation (delGJB6-D13S1830) in the GJB6 gene.

See related information sheet: Non-syndromic Hearing Loss, Autosomal Recessive GJB2 & GJB6

Disease condition

Hearing Impairment: Non-Syndromic, Autosomal Recessive

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