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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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CACNA1B Mutation Analysis

CACNA1B gene contains 47 exons spanning 246 kb of genomic DNA that was mapped to chromosome 9q34. The proteins (two isoforms) encoded by this gene, together with other four subunits encoded by different genes, forms the pore of the N-type voltage-dependent calcium channel, through which calcium enters the cell. This channel controls neurotransmitter release from neurons and is sensitive to omega-conotoxin-GVIA and omega-agatoxin-IIIA but insensitive to dihydropyridines. Multiple mutations in this gene were found to be associated with short-QT syndrome. CACNA1B mutations demonstrate autosomal dominant inheritance with a broad range of clinical severity both within and between families. Definitive genotype/phenotype correlations have not been described.

The John Welsh Cardiovascular Diagnostic Laboratory offers molecular genetic testing for CACNA1B mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the CACNA1B 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 short-QT syndrome (SQT).

Methodology

Genomic DNA is analyzed for CACNA1B mutations by automatic fluorescent DNA sequencing of the coding exons of the CACNA1B gene, as well as the exon/intron junctions and a portion of the 3' and 5' untranslated regions. 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 (Male or Female) $1,500 per sample 81407, G0452
Additional Family Members $300 per sample; known familial mutation only 81403, G0452

Sensitivity

DNA Sequencing Analysis: Approximately 99 percent detection of mutations in the coding exons 1-47 of CACNA1B.

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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