R183Q GNAQ Sturge–Weber Syndrome Leptomeningeal and Cerebrovascular Developmental Mouse Model

Abstract

Objective(s): Sturge–Weber syndrome (SWS), a rare neurovascular malformation disorder, is usually caused by the R183Q GNAQ somatic mosaic mutation enriched in brain endothelial cells. A developmental mouse model of SWS brain involvement is needed to investigate mutation impact upon brain vascular development and to facilitate preclinical drug studies. Methods: A new Tet-ON R183Q GNAQ transgenic mouse line was paired with rtTA tet transactivator mice under the Tie2 promoter to generate mice expressing endothelial R183Q GNAQ in the presence of doxycycline. Litters were perfused at P14-17; half received a subseizure dose (1.5 mg/kg; intraperitoneal) of kainate an hour before perfusion. A subset was perfused with Evans blue. Fixed mouse brains were stained with X-gal, DAPI, and antibodies for Gαq, Tie2, phosphorylated-S6, and claudin-5. Images were scored for vessel staining intensity. Results: X-gal staining was seen only in mutant mice; leptomeningeal endothelial X-gal staining was more frequent in kainate-treated mice (P < 0.001). When perfused with Evans blue, only mutant brains showed severe staining (P = 0.028). Median phosphorylated-S6 vessel scores were significantly higher in the leptomeninges of mutant mice (P = 0.035). Mutant cortical microvessels demonstrated discontinuous claudin-5 and phosphorylated-S6 staining as well as increased vessel length in kainate-treated mice (P = 0.024). Conclusions: The new R183Q GNAQ Tet-ON developmental mouse brain model of SWS demonstrates endothelial expression of mutant Gαq associated with blood–brain barrier breakdown, altered vascular mammalian target of rapamycin activity, and abnormal cortical microvessel structure. This new translational model can be used to develop new drug targets and treatments for SWS.