Gene Symbol: GJB2
Protein: Gap Junction Beta-2 Protein
Chromosomal Locus: 13q11-q12
Pseudonyms: CX26, DFNB1A, DFNA3A
TURNAROUND TIME: 10 business days
TESTING METHODOLOGY: Polymerase chain reaction (PCR) & DNA sequencing of exon 2 of the GJB2 gene.
- 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 40°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 15mg 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 (of congenital hearing loss): 1 to 6 in 1000
Inheritance: Of inherited forms, 70-80% is autosomal recessive, 23-30% is dominant, and 2-3% is X-linked. The GJB2 gene can cause recessive (DFNB1) or dominant (DFNA3) forms of hearing loss. DFNB1 accounts for approximately 50% of all congenital, severe-to-profound, ARNSHL in the United States.
Disease Characteristics: Significant hearing loss
Molecular Genetic Mechanism: A variety of missense, nonsense and insertion/deletion mutations have been described in the gene.
Clinical Sensitivity: 98% for DFNB1; 90% for DFNA3; 50% for all "congenital, severe to profound autosomal recessive non-syndromic hearing loss"- ARNSHL.
Analytic Sensitivity: >99%
Test Limitations: mutations outside exon 2 will not be detected (<1% of mutations).
INDICATIONS FOR USE:
- To determine the genetic basis for hearing loss in an affected individual.
- Isolated hearing loss in a family
- Individuals at risk due to family history who wish prenatal diagnosis.