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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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TGFB2 Mutation Analysis

The transforming growth factor-beta family of polypeptides (TGF-β1, TGF-β2 and TGF-β3) is involved in the regulation of cellular processes, including cell division, differentiation, motility, adhesion and death. TGF-beta signals by binding the TGF-beta type II receptor (TGFBR2), which transphosphorylates and activates the type I receptor (TGFBR1). Activated TGFBR1 then phosphorylates a subset of SMAD proteins, SMAD2 and SMAD3, which translocate to the nucleus where they form transcription complexes with DNA-binding factors and co-activators/co-repressors.

TGF-β2 is a secreted protein known as a cytokine that performs many cellular functions and has a vital role during embryonic development (alternative names: Glioblastoma-derived T-cell suppressor factor, G-TSF, BSC-1 cell growth inhibitor, Polyergin, Cetermin). It is an extracellular glycosylated protein and known to suppress the effects of interleukin dependent T-cell tumors. There are two named isoforms of this protein, created by alternative splicing of the same gene. The full-length TGFB2 gene contains 8 exons spanning 98.6 kb genomic distance that was mapped to chromosome 1q41. Mutations in the TGFB2 gene cause familial thoracic aortic aneurysms and dissections (TAAD) associated with mild systemic features of Marfan syndrome and Loeys-Dietz syndrome. TGFB2 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 TGFB2 mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the TGFB2 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 thoracic aortic aneurysms and dissections (TAAD), Marfan syndrome (MFS) and Loeys-Dietz syndrome (LDS).

Methodology

Genomic DNA is analyzed for TGFB2 mutations by automatic fluorescent DNA sequencing of the coding exons of the TGFB2 gene, as well as the exon/intron junctions and a portions 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 (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 99 percent detection of mutations in the coding exons of TGFB2.

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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