The stroke risk gene Foxf2 maintains brain endothelial cell function via Tie2 signaling

Stroke is a leading cause of death and long-term disability. In up to 30% of cases the underlying etiology is cerebral small vessel disease (SVD), the mechanisms of which are insufficiently understood. Genome-wide association studies have identified FOXF2 as a major risk gene for SVD and stroke. Foxf2 encodes a transcription factor that in the brain is primarily expressed in endothelial cells (ECs) and pericytes but the mechanisms linking Foxf2 to cerebrovascular disease are unknown. Here we show that Foxf2 maintains EC function via Tie2 signaling and limits infarct size in mice after middle cerebral artery occlusion. EC-specific inactivation of Foxf2 in adult mice resulted in blood-brain barrier leakage, which was exacerbated after experimental stroke compared to controls. Proteomic analyses of brain ECs from Foxf2 deficient mice as well as human pluripotent stem cell (iPSC) derived ECs lacking FOXF2 revealed a downregulation of multiple proteins involved in Tie2 signaling. We further found that endothelial Foxf2 deficiency compromises functional hyperemia, reduces endothelial NO production, and increases the size of experimentally induced infarcts via Tie2 signaling. Pharmacological treatment with the Tie2 activator AKB-9778 rescued the effects of Foxf2 deficiency on key outcomes. Moreover, RNA sequencing in combination with chromatin immunoprecipitation sequencing (ChIP-seq) in ECs revealed that FOXF2 functions as a transcriptional activator of Tie2 and other endothelial lineage-specific genes. Collectively, our results highlight the role of endothelial dysfunction and of reduced Tie2 signaling in SVD and stroke, thus offering new perspectives for therapeutic interventions.