Venous malformation-causative TIE2 mutations mediate an AKT-dependent decrease in PDGFB

Area of Science:

• Vascular biology
• Molecular genetics
• Cell signaling

Background:

• Endothelial cell (EC) tyrosine kinase receptor TIE2 mutations cause venous malformations.
• Specific mutations, L914F and R849W, exhibit distinct cellular behaviors.
• Pathogenic mechanisms of L914F remain largely uncharacterized.

Purpose of the Study:

• To investigate the molecular mechanisms underlying TIE2 L914F-induced venous malformations.
• To compare the global gene expression effects of L914F and R849W mutations in ECs.
• To elucidate the role of PDGFB production in TIE2-mutant ECs.

Main Methods:

• Global gene expression profiling of ECs with L914F mutation.
• In vitro and ex vivo analysis of PDGFB production in TIE2-mutant ECs.
• Investigation of AKT signaling pathway activation.

Main Results:

• L914F mutation profoundly dysregulates genes in vascular development, cell migration, and extracellular matrix processing.
• R849W mutation demonstrates only minor effects on gene expression.
• TIE2-mutant ECs exhibit deficient PDGFB production, mediated by ligand-independent AKT activation.
• This PDGFB deficiency contributes to abnormal vascular channels and smooth muscle cell paucity.

Conclusions:

• The L914F TIE2 mutation drives venous malformations through significant gene dysregulation and impaired PDGFB secretion.
• Chronic AKT activation by mutant TIE2 receptors underlies the PDGFB production defect.
• Reduced PDGFB is a key factor in the pathogenesis of TIE2-related venous malformations.