Expression of mutant TIE2 p.L914F during mouse development causes embryonic lethality and defects in vascular remodeling.

Background: Sporadic venous malformation (VM) is associated with the hyperactivating p.L914F mutation in TIE2, a receptor tyrosine kinase essential for vascular development. This mutation is not found in hereditary VM, suggesting incompatibility with life when expressed during early vascular development. Therefore, we utilized a genetic mouse model that expresses TIE2 p.L914F to determine its phenotypical effects during development.

Results: B6-Tg(Rosa26-TIE2^L914F)^EBos (TIE2^L914F) mice were generated and then validated for the presence of the transgene. The constitutive endothelial-specific Tie2-Cre line was used to activate expression of the mutant gene during early embryonic development. Tie2-Cre;TIE2^L914F embryos experienced lethality at approximately embryonic day (E)9.5. Three-dimensional imaging of embryos and yolk sacs revealed impaired vascular remodeling in mutant animals, resulting in malformed vasculature with disorganized, dilated, and non-functional blood vessels. The abnormal yolk sac vascular phenotype was not associated with total loss of erythroid cells or increased cell proliferation.

Conclusions: The TIE2^L914F mice used in this study represent a novel genetic model of TIE2 p.L914F-driven vascular disease. This study provides the first experimental evidence that this mutation is incompatible with early prenatal development due to its deleterious effects on the vasculature, illustrating the vital role of balanced TIE2 signaling during vessel development and remodeling.