An essential role for Rac1 in endothelial cell function and vascular development.

Area of Science:

• Endothelial cell biology
• Vascular development
• Small GTPase signaling

Background:

• Cell surface receptors regulate endothelial cell function and vascular development.
• Intracellular signaling pathways, including Ras and Rho GTPases, are activated by these receptors.
• The precise role of these signaling molecules in endothelial cell activities remains unclear.

Purpose of the Study:

• To investigate the role of the Rho-related GTPase Rac1 in endothelial cell function and vascular development.
• To examine Rac1's contribution to endothelial cell migration, tubulogenesis, adhesion, and permeability.
• To determine the in vivo consequences of endothelial Rac1 deletion on embryonic vascular development.

Main Methods:

• Utilized a conditional Cre/Flox system for endothelial-specific deletion of the Rac1 gene.
• Assessed Rac1 function in primary endothelial cells in vitro.
• Analyzed vascular development in Rac1-deficient embryos and yolk sacs.

Main Results:

• Rac1 deficiency in endothelial cells impaired migration, tubulogenesis, adhesion, and permeability in response to VEGF and S1P.
• Rac1-deficient endothelial cells failed to form lamellipodia, focal adhesions, and remodel cell-cell contacts.
• Endothelial-specific Rac1 deletion caused mid-gestation embryonic lethality (around E9.5).
• Defective development of major vessels and absence of small branched vessels were observed in deficient embryos and yolk sacs.

Conclusions:

• Rac1 activity is crucial for endothelial cell function, including migration and tubulogenesis.
• Endothelial Rac1 is essential for embryonic vascular development, encompassing both major and branched vessel formation.
• Rac1 and its downstream effectors are potential therapeutic targets for diseases involving abnormal neovascularization.