Figure 2. Expression of arteriovenous markers. The expression of arterial, capillary, and venous markers, as defined by single-cell analysis of the brain vasculature [32], is shown on tSNE plots that display the retinal microvascular endothelial cells (RMECs) arranged by overall transcriptome similarity. The aim is to establish whether differences in gene expression between the cells might reflect their origin from different regions of the arteriovenous tree. The majority of cells express genes characteristic of capillaries with very few expressing two of three arterial or venous markers. The discrepant expression of Vegfc and Nr2f2 may be due to species differences, the retinal rather than brain origin of the vessels, or a change in phenotype in culture. The broad expression of most capillary markers, and lack of consistent expression of arterial or venous markers in a subset of cells, suggests that most of the cells originate from capillaries.