Connexin 30

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CONNEXIN 30

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.
 
SPECIMEN REQUIREMENTS:
  • 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.

Note:
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.
 
INTERPRETATIVE DATA:
 
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.
ADDITIONAL RESOURCES:
 
Genetics Home Reference: ghr.nlm.nih.gov/gene/GJB2
Gene Reviews for DFNA3: www.ncbi.nlm.nih.gov/books/NBK1536
Gene Reviews for DFNB1: www.ncbi.nlm.nih.gov/books/NBK1272