Hereditary cutaneomucosal venous malformations are caused by TIE2 mutations with widely variable...

Area of Science:

• Vascular biology
• Genetics
• Dermatology

Background:

• Autosomal dominant cutaneomucosal venous malformation (VMCM) is linked to mutations in the TIE2/TEK gene.
• Previously, only two germline TIE2/TEK substitutions (R849W, Y897S) in the kinase domain were reported in five families.
• These known mutations increase ligand-independent TIE2 receptor phosphorylation fourfold.

Purpose of the Study:

• To identify novel TIE2/TEK mutations associated with VMCM.
• To investigate the functional consequences of these new mutations on TIE2 receptor activity.
• To explore the phenotypic spectrum and molecular mechanisms of VMCM.

Main Methods:

• Genetic sequencing to identify mutations in affected families.
• Analysis of mutation locations within the TIE2/TEK gene (tyrosine kinase, kinase insert, carboxy-terminal tail).
• Overexpression studies to assess ligand-independent phosphorylation and receptor activation levels.

Main Results:

• Twelve new families with TEK mutations were identified, expanding the known mutation spectrum.
• Six novel mutations were discovered, alongside six instances of the R849W substitution.
• Overexpression of new mutants confirmed ligand-independent hyperphosphorylation, a hallmark of VMCM-causing TIE2 mutations.
• Demonstrated varying levels of TIE2 hyperphosphorylation are tolerated in heterozygotes, supporting normal endothelial function outside lesion sites.

Conclusions:

• TEK mutations are a significant cause of VMCM, with ligand-independent hyperphosphorylation being a consistent molecular mechanism.
• The study expands the known genetic and phenotypic landscape of VMCM, including cutaneous, mucosal, and cardiac manifestations.
• Differential levels of TIE2 hyperactivation are tolerated, suggesting context-dependent pathogenicity in endothelial cells.