Whole Blood, Saliva, or Buccal Swabs

Must include the following information:

• Patient identifiers (full name, date of birth, sex and medical record number)
• Pertinent history and clinical findings
• Date of collection & sample type
• Ordering physician

Samples may be refrigerated if delivery is delayed.

Blood: 3-5cc EDTA Whole Blood- room temp
Saliva: DNA Genotek, ORAGene Discover, OGR-500
Buccal Swabs: DNA Genotek, OraCollect, OCD-100, at least 4 swabs

Samples accepted Monday-Friday.

4 weeks

None detected

DFNB1
Two different genes cause hearing loss at this locus, which maps to chromosome 13q11-q12:GJB2, encoding Connexin 26; and GJB6, encoding Connexin 30.

GJB2 (encodes Connexin 26, CX26)
CX26 (OMIM#: *121011) is a gap junction protein expressed in the supporting cells of the cochlea. The gene, GJB2, contains 2 exons, the second of which encodes the 226 amino acid protein CX26. Variants in GJB2 are found in ~50% of persons with autosomal recessive nonsyndromic hearing loss. Over 100 different variants have been identified.

GJB6 (encodes Connexin 30, CX30)
CX30 (OMIM#: *604418) is also a gap junction protein. Lerer and colleagues identified a deletion upstream of GJB2, which included the first exon of GJB6 in 2001. Del Castillo and colleagues characterized this deletion as a 342kb fragment of chromosome 13 that included D13S1830 in addition to a portion of GJB6, and so this deletion is commonly known as the del(GJB6-D13S1830) variant. It segregates with variants in GJB2 to cause recessively inherited deafness at the DFNB1 locus. A recent multicenter study investigating the variant spectrum in over 1500 deaf persons from 16 countries found this variant to represent 1.67% of variants at the DFNB1 locus (Van Camp, et al. 2005). A second smaller deletion, del(GJB6-D13S1854), also causes deafness at the DFNB1 locus.

Sensitivity is greater than 98%.

Please print, complete and submit the Hearing Loss Testing Requisition Form from the Molecular Otolaryngology & Renal Research Laboratories, to Specimen Control/Mailouts with the specimen and the Epic Requisition.

1. Direct sequence analysis of coding region of GJB2 including analysis of intron/exon boundaries.
2. Screening for the del(GJB6-D13S1830) and del(GJB6-D13S1854) variants completed by PCR amplification of oligonucleotide primers flanking and within the deletion breakpoints; products resolved on an agarose gel and sized to determine presence or absence of a deletion.

GJB2 - 81252
GJB6 - 81254