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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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ACTA2 Mutation Analysis

Smooth muscle alpha actin belongs to the actin family of proteins, which are highly conserved proteins that play a role in cell motility, structure and integrity. Alpha, beta and gamma actin isoforms have been identified, with alpha actins being a major constituent of the contractile apparatus, whereas beta and gamma actins are involved in the regulation of cell motility. This actin is encoded by the ACTA2 gene, which is composed of eight coding exons and is located at 10q22-q24. Defects in this gene cause familial thoracic aortic aneurysm/dissection type 6 (AAT6), which is one of the most severe cardiovascular conditions in adults. At least nine ACTA2 mutations have been identified in several families to date. Mutations in ACTA2 are estimated to be responsible for 14 percent of familial thoracic aortic aneurysms. Associated findings in AAT6 caused by ACTA2 mutations may include livedo reticularis, a bicuspid aortic valve, iris flocculi and patent ductus arteriosus. AAT6 demonstrates autosomal dominant inheritance. Definitive genotype/phenotype correlations have not been described.

The John Welsh Cardiovascular Diagnostic Laboratory offers molecular genetic testing for ACTA2 mutations. Individuals are tested by automatic fluorescent DNA sequencing of the eight coding exons (exons 2-9) of the ACTA2 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 familial thoracic aortic aneurysm/dissection type 6 (AAT6)

Methodology

Genomic DNA is analyzed for ACTA2 mutations by automatic fluorescent DNA sequencing of eight coding exons of the ACTA2 gene, as well as the exon/intron junctions and a portion of the 5` and 3` 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(s) by automatic fluorescent DNA sequencing.

Service Fees

Service Direct and Institutional Billing CPT Codes
Index Case (Male or Female) $750 per sample 81405, G0452
Additional Family Members $300 per sample; known familial mutation only 81403, G0452

Sensitivity

DNA Sequencing Analysis: Approximately 95 percent detection of mutations in exons 2-9 of ACTA2

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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