Endothelial Notch4 signaling induces hallmarks of brain arteriovenous malformations in mice

Abstract

Brain arteriovenous malformations (BAVMs) can cause devastating stroke in young people and contribute to half of all hemorrhagic stroke in children. Unfortunately, the pathogenesis of BAVMs is unknown. In this article we show that activation of Notch signaling in the endothelium during brain development causes BAVM in mice. We turned on constitutively active Notch4 (int3) expression in endothelial cells from birth by using the tetracycline-regulatable system. All mutants developed hallmarks of BAVMs, including cerebral arteriovenous shunting and vessel enlargement, by 3 weeks of age and died by 5 weeks of age. Twenty-five percent of the mutants showed signs of neurological dysfunction, including ataxia and seizure. Affected mice exhibited hemorrhage and neuronal cell death within the cerebral cortex and cerebellum. Strikingly, int3 repression resolved ataxia and reversed the disease progression, demonstrating that int3 is not only sufficient to induce, but also required to sustain the disease. We show that int3 expression results in widespread enlargement of the microvasculature, which coincided with a reduction in capillary density, linking vessel enlargement to Notch's known function of inhibiting vessel sprouting. Our data suggest that the Notch pathway is a molecular regulator of BAVM pathogenesis in mice, and offer hope that their regression might be possible by targeting the causal molecular lesion.angiogenesis ͉ cell signaling ͉ endothelial cell ͉ stroke ͉ cerebrovascular

Constitutively active Notch4 receptor elicits brain arteriovenous malformations through enlargement of capillary-like vessels

“…S5). We observed, as we have previously published (15)(16)(17), that advanced AVMs exhibited increased SMA staining. Thus, the absence of SMCs in the initial AV shunts is consistent with a capillary origin of AVMs in the Tie2-Notch4* mice.…”

“…ECs results in spontaneous AVMs in mice (15)(16)(17)21). Although this work has facilitated new research directions regarding the Notch pathway in AVMs, how aberrant Notch signaling leads to AVM remains unknown.…”

“…The Notch receptors are transmembrane proteins that promote arterial endothelial cell (EC) specification by enhancing expression of arterial molecular markers and suppressing the expression of venous markers (12)(13)(14)(15)(16)(17)(18)(19). Abnormal signaling induces enlarged AV connections and shunting in mouse and zebrafish embryos (12)(13)(14).…”

Reducing Jagged 1 and 2 levels prevents cerebral arteriovenous malformations in matrix Gla protein deficiency

“…Gene deletion of Dll4 and Hey1/Hey2 in mice leads to reduce expression of the arterial marker Ephrin B2 (22,27,28) and enhanced expression of the venous marker Eph B4 (29). Constitutively active Notch4 increases expression of Ephrin B2 in the brain vasculature and causes cerebral AVMs (10), and loss of function of Ephrin B2 and Eph B4 affects vascular remodeling and intercalation of arterial and venous vasculature (30). We showed that an increase in Ephrin B2 and a decrease in Eph B4 are associated with AVMs in the Mgp −/− mice, which is consistent with the previous studies.…”

“…Mutations in the genes for activin-like kinase receptor 1 (ALK1), a BMP type I receptor, and Endoglin, a coreceptor of ALK1, cause hereditary hemorrhagic telangiectasia (HHT) characterized by the presence of AVMs in multiple organs including the brain (6)(7)(8)(9). Enhanced endothelial Notch signaling, as mediated by constitutively active Notch4, also promotes the formation of brain AVMs, whereas normalization of Notch4 activity results in regression of arteriovenous (AV) shunts (10,11).…”