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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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AKAP9 Mutation Analysis

A-Kinase Anchoring Protein 9 (AKAP9) is a member of the A-kinase anchor proteins (AKAPs) family, which is comprised of structurally diverse proteins that have the common function of binding to the regulatory subunit of protein kinase A (PKA) and confining the holoenzyme to discrete locations within the cell. Human AKAP9 gene encodes a full-length protein of 3907 amino acids. Alternate splicing of this gene results in at least two isoforms that localize to the centrosome and the Golgi apparatus and interact with numerous signaling proteins from multiple signal transduction pathways. AKAP9 gene contains 50 exons spanning around 170 kb of genomic distance that was mapped to chromosome 7q21-q22. Multiple mutations in AKAP9 have been identified in patients with long-QT syndrome type 11 (LQT11), breast cancer and colorectal cancer. AKAP9 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 AKAP9 mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the AKAP9 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 long-QT syndrome type 11 (LQT11).

Methodology

Genomic DNA is analyzed for AKAP9 mutations by automatic fluorescent DNA sequencing of the coding exons of the AKAP9 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) $1650 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 coding exons 1-50 of AKAP9.

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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