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Cascade testing for GJB2 gene mutation (for Connexin 26) – early non-syndromic AR deafness

Test covered by the reimbursement:

YES

Test without reimbursement:

YES

Gender:

Woman/Man

Material:

Peripheral blood, Buccal swab …

Turnover time:

3 weeks

STATIM:

1 week

Material:

Peripheral blood | 1x 3 ml of whole blood in K3 EDTA tube

Storage after examination: week after the report is issued 2 – 8°C

Buccal swab | 2x swab stick for buccal swab collection

Storage after examination: week after the report is issued 2 – 8°C

Isolated DNA from blood | 10–100 ng/μL of isolated DNA from blood in a PCR tube of at least 15 μL.

Storage after examination: stored in a DNA archive without restriction 15°C

Isolated DNA from chorionic villi | 30–100 ng/μL of isolated DNA from chorionic villi in a microtube (Eppendorf type)

Storage after examination: stored in a DNA archive without restriction 15°C

Isolated DNA from amniotic fluid | 30–100 ng/μL of isolated DNA from amniocentesis in a microtube (Eppendorf type)

Storage after examination: stored in a DNA archive without restriction 15°C

Isolated DNA from cordocentesis | 30–100 ng/μL of isolated DNA from cordocentesis in a microtube (Eppendorf type)

Storage after examination: stored in a DNA archive without restriction 15°C

DNA isolated from the product of conception | 50–100 ng/μL in microtube (Eppendorf type)

Storage after examination: stored in a DNA archive without restriction 15°C

DNA isolated from cultured cells | 30–100 ng/μL of isolated DNA from cultured cells in a microtube (Eppendorf type)

Storage after examination: stored in the DNA archive 15°C

Quick test description:

Testing for GJB2 gene mutations (gap junction beta 2) responsible for hereditary autosomal recessive disease, early non-syndromic disorder/hearing loss and deafness, also referred to as DFNB1.

Test details:

The test is performed to detect mutations in the GJB2 gene.

GJB2 (gap junction beta 2) gene mutations are responsible for hereditary autosomal recessive disease – early non-syndromic disorder/hearing loss and deafness, also referred to as DFNB1, with an approximate incidence of 1:5,000 live births. Hearing loss in those affected is always perceptual (sensorineural) and prelingual (early) – before speech development.

In the Czech population, the 35delG mutation is prevalent (80% of pathogenic alleles); other common mutations include: W24X (prevalent in Roma ethnic group), 313del14, 120delE, L90P, IVS1+1G→A.

GJB2 gene testing and detection of mutations is carried out according to principles intended to ensure the efficiency and reliability of testing. Due to the high prevalence of the most common mutation (35delG), each sample is tested using a simplified test targeting only this mutation. The 35delG mutation is detected by real-time PCR.

If a deaf patient is found to be non-homozygous for a 35delG mutation (i.e. heterozygous for the mutation or homozygous for the normal (wt) allele), sequencing of the entire exon 2 in the GJB2 gene (i.e. the entire coding region) follows. If the 35delG mutation is not detected in the hearing patient, sequencing of the entire exon 2 in the GJB2 gene follows. Exon 1 is only tested in selected patients, based on the diagnosis and medical history. Both exons in the GJB2 gene (exon 1 and exon 2) are sequenced by Sanger sequencing.