Identifying novel mutations driving the formation of stroke-causing brain vascular malformations.
Intracranial vascular malformations manifest on a continuum ranging from predominantly arterial to predominantly venous in pathology. Cerebral cavernous malformations (CCMs) are capillary malformations, which exist at the midpoint between the two ends of thise continuum. The axon guidance factor Ephrin B2 and its receptor EphB4 are critical regulators of vasculogenesis in the developing central nervous system and dysregulation of Eephrin B2 / EephB4 has been implicated in the pathogenesis of arterial-derived arteriovenous malformations (AVMs) and vein-based vein of Galen malformations (VOGMs). There is increasing evidence supporting the hypothesis that aberrant Ephrin B2/EphB4We signaling may be contributory to the development of vascular malformations, but the role of this pathways in CCMs remain largely uncharacterized. Evidence of Ephrin dysregulation in CCMs would be important as a common link hypothesized Ephrin B2/EphB4 dysregulation has that ephrin signaling would also be impaired in CCMs and that validation of this hypothesis would link the entire spectrum of structural cerebrovascular lesions to dysregulation of a shared common pathway. By studying patient-derived primary CCM endothelial cells (CCMECs), we established that CCMECs are functionally distinct from healthy endothelial cell controls and demonstrate altered patterns of migration and motility with impaired tube formation. CCMECs have an increased EphrinB2/EphB4 ratio and whole exome sequencing identified mutations in both EphrinB2 and EphB4. As a proof of concept, The identified mutation in the EPHB4 gene was introduced in endothelial HUVEC cells. We found that the identified mutation alters the EphrinB2/EphB4 binding, affects cellular morphology, and diminishes tube formation capacity. These findings identify functional alterations in the EphrinB2/ EphB4 ratio as a feature linking pathophysiology across the spectrum of arterial, capillary and venous structural malformations in the central nervous system while also revealing a putative therapeutic target.
Selected Publications:
Sesen J., Ghalali A., Driscoll J., Martinez T., Lupieri A., Zurakowski D., Alexandrescu S., Smith E.R., Fehnel K.P., Discovery and Characterization of Ephrin B2 and EphB4 Dysregulation and Novel Mutations in Cerebral Cavernous Malformations: In Vitro and Patient-Derived Evidence of Ephrin-Mediated Endothelial Cell Pathophysiology. Cell Mol Neurobiol. 2023 Dec 27;44(1):12.