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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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CACNB2 Mutation Analysis

CACNB2 codes for the 660-amino acid β2-subunit (Cavβ2) of Cav1.2, which modifies gating and increases the IL, Ca current. It contributes to the function of the calcium channel by increasing peak calcium current, shifting the voltage dependencies of activation and inactivation, modulating G protein inhibition and controlling the a-1 subunit membrane targeting. CACNB2 consists of 14 exons covering 421-kb genomic distance at chromosome 10p12. Cavβ2 functions as a chaperone for the a-subunit of Cav1.2, ensuring its transport to the plasma membrane. It is the dominantly expressed Cav1.2β-subunit in the heart. It has been reported that CACNB2 mutations can lead to Brugada syndrome type 4, characterized by ST-segment elevation in the right precordial leads and sudden death due to ventricular tachycardia/ventricular fibrillation in the absence of structural heart disease. Definitive genotype/phenotype correlations have not been described.

The John Welsh Cardiovascular Diagnostic Laboratory offers molecular genetic testing for CACNB2 mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the CACNB2 gene. We strongly recommend initial testing of a clearly affected individual, if available, in order to provide the greatest test sensitivity and clearest interpretation of results for subsequent family members. Genetic counseling is recommended for all individuals.

Reasons for Referral

Molecular confirmation of the diagnosis of Brugada syndrome type 4.

Methodology

Genomic DNA is analyzed for CACNB2 mutations by automatic fluorescent DNA sequencing of the coding exons of the CACNB2 gene, as well as the exon/intron junctions and a portion of the 5' and 3' untranslated region. Patient DNA is sequenced in both the forward and reverse orientations. If a mutation is identified, additional family members are analyzed only for the familial mutation by automatic fluorescent DNA sequencing.

Service Fees

Service Direct and Institutional Billing CPT Codes
Index Case (Full Gene) $1000 per sample 81406, G0452
Additional Family Members $300 per sample; known familial mutation only 81403, G0452

Sensitivity

DNA Sequencing Analysis: Approximately 99 percent detection of mutations in coding exons 1-14 of CACNB2.

Specimen Requirements

Blood (preferred): EDTA (purple-top) tubes: Adult: 5 cc, Child: 5 cc, Infant: 2-3 cc
Tissue: Frozen (preferred), RNAlater, Formalin-fixed, Paraffin-embedded
Other Body Fluids: Call to inquire
Buccal Swabs: One swab from each cheek

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