Rationale:
Sturge-Weber syndrome is a rare, congenital, neurovascular malformation disorder; children have a somatic mosaic mutation enriched in endothelial cells, a leptomeningeal and cortical vascular malformation that enhances with gadolinium on MRI, and early onset of seizures accompanied by neurologic deterioration. Newly published data (Valery et al. 2024 ACNS) suggests that neurologic outcome may be modifiable; presymptomatic treatment initiated prior to seizure onset can prevent or delay early-onset seizures< 2 years old and improve 2-year-old neurologic function. Previously published (Solomon et al. 2024 JOVA) tetO-GNAQ*R183Q X Tie2-rtTA/TRE-βGal developmental mouse model demonstrates impaired blood-brain-barrier function at P15, malformed cortical vessels, and increased leptomeningeal vascular mTOR expression. We assessed seizure susceptibility in this model, seizure mortality, and the impact of early seizures upon mutant protein expression and the vascular malformation.
Methods:
Kainate (2 or 2.5 mg/kg/dose i.p.) was administered at P15 and mice observed in a 35° C incubator. Seizure severity was scored every 5 minutes for 2.5 hours (utilizing published modified Racine scale for immature mice). Seizures were scored prior to genotyping the mice. Mice were perfused 48 hours later, and brains collected, flash frozen, post-fixed, sectioned and stained for X-gal (marker for mutant Gαq expression), dapi, TIE2, p-S6, and claudin-5. Brain images were quantified, by an observer blinded to mouse genotype, with a previously published scale, ImageJ and AngioTool.
Results:
Immature mutant mice demonstrated greater mortality compared to littermate controls after 2.5 mg/kg kainate (Figure 1, panel A; p< 0.005) and more severe seizures after either (Figure1, panels B-D; p< 0.05 each, one-way for the ANOVAs). After 2 mg/kg kainate, mutant mice displayed an increased and more frequent endothelial X-gal expression (Figure 2, panel A; p< 0.001), and greater cortical micro-vessel length and density, compared to both previously published mutants at P15 (Figure 2, panel A; p< 0.01 each) and to littermate controls (p< 0.05 each). Decreased, more discontinuous claudin-5 expression (Figure 2, panel B; p< 0.005) was also noted, but no difference in leptomeningeal endothelial p-S6 expression, in mutants versus littermate controls.