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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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SCN3B Mutation Analysis

Voltage-gated sodium channels are transmembrane glycoprotein complexes composed of a large alpha subunit and one or more regulatory beta subunits. They are responsible for the generation and propagation of action potentials in neurons and muscle. SCN3B gene encodes one member of the sodium channel beta subunit gene family, and influences the inactivation kinetics of the sodium channel. This gene contains six exons (1 noncoding) spanning 26 kb of genomic distance that has been mapped to chromosome 11q23.3. Two alternatively spliced variants, encoding the same protein, have been identified. Defects in this gene cause Brugada syndrome type 7 (BRS7). SCN3B mutations demonstrate autosomal dominant inheritance with a broad range of clinical severity both within and between families.

The John Welsh Cardiovascular Diagnostic Laboratory offers molecular genetic testing for SCN3B mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the SCN3B 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 7 (BRS7).

Methodology

Genomic DNA is analyzed for SCN3B mutations by automatic fluorescent DNA sequencing of the coding exons of the SCN3B 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) $750 per sample 81404, 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 1-5 of SCN3B.

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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