Endothelial GNAQ p.R183Q activates phospholipase-Cbeta3, increases angiopoietin-2 and drives formation of enlarged blood vessels

Introduction: Capillary malformation (CM) occurs sporadically and is associated with Sturge-Weber syndrome (SWS). The somatic mosaic mutation in GNAQ (c.548GàA, p.R183Q) is enriched in endothelial cells (EC) in skin CM and SWS brain CM. Our goal was to investigate how the mutant G-protein a-q subunit (Gaq) alters EC signaling and disrupts capillary morphogenesis. Approach and results: We used lentiviral constructs to express p.R183Q or wild-type GNAQ in normal human endothelial colony forming cells (EC-R183Q and EC-WT respectively). EC-R183Q constitutively activated phospholipase-C ß3 (PLCß3), a downstream effector of Gaq. Activated PLCß3 was also detected in human CM tissue sections. Bulk RNA-seq analyses of mutant versus wild-type EC indicated constitutive activation of protein kinase C (PKC), NF-?B and calcineurin signaling in EC-R183Q. Increased expression of downstream targets in these pathways, Angiopoetin-2 (ANGPT2), C-X-C Motif Chemokine Ligand 5 (CXCL5) and Down Syndrome Critical Region Protein 1.4 (DSCR1.4) were confirmed by qPCR and immunostaining of human CM tissue sections. The Gaq inhibitor YM-254890 reduced mRNA expression levels of these targets in EC-R183Q while the pan-PKC inhibitor AEB071 reduced ANGPT2 and CXCL5 but not DSCR1.4. EC-R183Q formed enlarged blood vessels in mice, reminiscent of those found in human CM, with robust endothelial ANGPT2. Conclusions: Gaq-R183Q, when expressed in ECs, establishes constitutively active PLCb3 signaling that leads to a pro-angiogenic, pro-inflammatory phenotype. EC-R183Q are sufficient to form CM-like vessels in mice which provides the first evidence that endothelial Gaq-R183Q is causative for CM. Overall design: Examination of the effects of the p.R183Q mutation in GNAQ on gene expression and blood vessel function in human endothelial colony-forming cells (ECs).