Arteries and veins are structurally and functionally distinct vessels that circulate blood away from and towards the heart, respectively. Notch signalling determines arterial specification during development whereas the orphan nuclear receptor COUP-TFII (also known as NR2F2) promotes venous specification by inhibiting Notch signalling in a subset of endothelial cells. But what regulates COUP-TFII expression in veins? Courtney Griffin and co-workers now report () that the chromatin remodelling enzyme BRG1 promotes COUP-TFII expression and venous specification during mouse embryogenesis. The researchers show that genetic depletion of Brg1 downregulates COUP-TFII expression and leads to aberrant expression of arterial markers in developing veins. BRG1 promotes the expression of COUP-TFII, they report, by binding to regulatory elements within the COUP-TFII promoter and remodelling the chromatin to increase the promoter’s accessibility to the transcriptional machinery. These data describe for the first time a factor that promotes COUP-TFII expression in developing veins and broaden our understanding of how epigenetic processes influence vascular development.
