Gene Symbol: GJB6
Chromosomal Locus: 13q12.11
Protein: Gap Junction beta-6 Protein
Pseudonyms: CX30; GJB6-D13S1830; gap junction protein, beta-6, 30KDa; DFNA3B, DFNB1B
TURNAROUND TIME: 10 business days
TESTING METHODOLOGY: Mutation specific multiplex polymerase chain reaction (PCR) for the common 342kb deletion.
- Collect: Prefer two 5ml whole blood EDTA (lavender top) tube.
- Min. Collection: 0.7 ml whole blood EDTA.
- Transport: blood EDTA at Room Temp shipped regular next day air (No Saturday delivery; store specimen at 4°C and ship Monday).
- Stability: Ambient: up to 7 days; Refrigerated: 2 weeks. Frozen: unacceptable
- Unacceptable Conditions: Serum. Frozen or severely hemolyzed blood. Clotted blood.
- Prenatal testing: Direct: 5ml direct unspun amniotic fluid or 3mm3 CVS tissue with a backup flask growing. Culture: confluent T25 flask. Maternal blood sample is required for maternal cell contamination studies.
A Molecular Genetics Laboratory Test Requisition must accompany the specimen. Contact the Molecular Laboratory at 918-502-1721 to obtain further information.
Counseling and informed consent are recommended for genetic testing; Center for Genetic Testing at Saint Francis consent form
is available as a resource but not required.
Incidence (Congenital hearing loss): 1 to 6 in 1000
Inheritance: A single CX30 mutation can act with a single CX26 mutation to cause recessive hearing loss. Therefore, they are often tested as a panel. Nonsyndromic hearing loss is caused by mutations in the CX26 and CX30 genes in 50% of cases. Of this type of hearing loss, 70-80% is autosomal recessive, 20-30% is dominant. The CX30 gene can cause recessive (DFNB1) or dominant (DFNA3) forms of hearing loss. The 342 Kb deletion is associated with recessive hearing loss.
Disease Characteristics: Significant hearing loss at a young age; in some cases it can be progressive.
Molecular Genetic Mechanism: A large deletion (342kb) interrupting the CX30 gene.
Clinical Sensitivity: 1% for DFNB1. The CX30 deletion accounts for a small portion of DFNB1 hearing loss. However, it has been found in a higher percentage of individuals having a single CX26 change. Greater than 90% of mutations in the CX30 gene are due to the 342kb deletion.
Analytic Sensitivity: >99%
Test Limitations: Mutations other than the common 342kb deletion will not be detected.
INDICATIONS FOR USE:
- To identify a second mutation in patients who carry a single CX26 mutation.
- To determine the genetic basis for hearing loss in an affected individual.
- Individuals at risk due to family history who wish prenatal diagnosis.