Capillary malformations (CMs) are congenital vascular lesions caused by somatic mutations in the GNAQ gene, most frequently resulting in a p.R183Q substitution in the Gαq protein in endothelial cells. However, the downstream signaling pathways by which Gαq-R183Q impairs vascular function remain poorly defined. To address this, we generated human dermal endothelial cells lacking endogenous Gαq and expressing the Gαq-R183Q mutan...