Genetic dysregulation of an endothelial Ras signaling network in vein of Galen malformations

Abstract

To elucidate the pathogenesis of vein of Galen malformations (VOGMs), the most common and severe congenital brain arteriovenous malformation, we performed an integrated analysis of 310 VOGM proband-family exomes and 336,326 human cerebrovasculature single-cell transcriptomes. We found the Ras suppressor p120 RasGAP (RASA1) harbored a genome-wide significant burden of loss-of-function de novo variants (p=4.79x10-7). Rare, damaging transmitted variants were enriched in Ephrin receptor-B4 (EPHB4) (p=1.22x10-5), which cooperates with p120 RasGAP to limit Ras activation. Other probands had pathogenic variants in ACVRL1, NOTCH1, ITGB1, and PTPN11. ACVRL1 variants were also identified in a multi-generational VOGM pedigree. Integrative genomics defined developing endothelial cells as a key spatio-temporal locus of VOGM pathophysiology. Mice expressing a VOGM-specific EPHB4 kinase-domain missense variant exhibited constitutive endothelial Ras/ERK/MAPK activation and impaired hierarchical development of angiogenesis-regulated arterial-capillary-venous networks, but only when carrying a second-hit allele. These results illuminate human arterio-venous development and VOGM pathobiology and have clinical implications.

Pediatric Cerebral Vascular Malformations : Current and Future Perspectives

“…It is becoming increasingly apparent that many AVMs and VOGMs are vein-based lesions, arising in association with mutations affecting one of two canonical pathways – ephrins ( EPHB4 ) and HHT ( HHT1 , also called ENG ; and HHT2 , also called ACVRL1 ) – that direct endothelial differentiation in development [ 6 , 16 , 25 , 67 , 68 ]. In contrast, while CMs also have dysfunctional endothelial cells, there is a distinct family of genes related to capillary formation that drive their growth, including the related CCM genes ( CCM1 , CCM2 , and CCM3 ), with only limited overlap with the ephrin pathway [ 12 , 25 , 53 ].…”

“…However, many of the sporadic lesions – the most common in pediatric neurosurgical practice – arise from somatic mutations in the ephrin pathway, usually KRAS or BRAF ; downstream drivers of cell invasion and proliferation [ 25 ]. Given that ephrin is the cell surface-based receptor upstream of a pathway that subsequently controls the downstream intracellular molecules RASA1 , KRAS , BRAF , and RAS , there is now basis for a biological connection between ephrin and RAS mutations in VOGM, RASA1 mutations in AVM and AV fistulas and the aforementioned KRAS and BRAF mutated nidal AVMs – demonstrating how mutations in interrelated molecules in a specific pathway can manifest similar phenotypes [ 7 , 16 , 25 , 67 , 68 ].…”

Endothelial samplingin situenables genetic characterization of vein of Galen Malformation

“…7,8 Functional genomics approaches such as single-cell RNA sequencing (scRNA seq) delineate molecular mechanisms underlying diseases with a genetic or shared molecular component. [9][10][11][12][13][14][15][16] Collectively, these approaches may enable (1) detection of potential causative or risk-conferring mutations; (2) elucidation of cellular composition in situ; and (3) identification of convergent molecular mechanisms amenable to pharmacologic or even gene therapy based approaches.…”