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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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KCNE3 Mutation Analysis

The KCNE3 gene encodes the 103-amino acid peptide MiRP2, one of five homologous ancillary β-subunits (KCNE peptides) of voltage gated potassium ion channels. The KCNE3 gene consists of 3 exons distributed over 13-kb genomic interval at chromosome 11q13-q14; only the last exon is translated. KCNE3 forms a constitutively open potassium channel with KCNQ1 (a-subunit). It modulates the function of Kv4.3 (encoded by KCND3) as an inhibitory β-subunit, changes KCNQ1 properties to yield currents that are nearly instantaneous and depend linearly on voltage, and suppresses the currents of KCNQ4 and HERG potassium channels. Mutations in KCNE3 that lead to the gain of function of transient outward potassium current (Ito) may underlie the pathogenesis of Brugada Syndrome type 6, a genetically heterogeneous and hereditable disorder characterized by ST-segment elevations in the right precordial electrocardiogram (ECG) leads, associated with a high incidence of syncope or sudden death due to ventricular tachyarrhythmias. Definitive genotype/phenotype correlations have not been described.

The John Welsh Cardiovascular Diagnostic Laboratory offers molecular genetic testing for KCNE3 mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the KCNE3 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 6.

Methodology

Genomic DNA is analyzed for KCNE3 mutations by automatic fluorescent DNA sequencing of the coding exons of the KCNE3 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) $500 per sample 81403, 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 of KCNE3.

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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