Zouine, k.; Sarhrout, W. M.; Megne, A. V.; OUBAHA, M.

Arteriovenous endothelial identity coordinates vascular growth and patterning, but whether it is remodeled during developmental vessel regression remains unknown. The mouse hyaloid vasculature is a transient ocular network considered predominantly arterial; its timely regression is required for normal vision, yet the identity of its regressing endothelium has remained largely unexplored. Here, we show that postnatal regression is accompanied by a shift from ephrin-B2-enriched to EphB4-enriched endothelium. Residual ephrin-B2-positive endothelial cells increasingly displayed cleaved caspase-3 labeling, whereas Ki67 positivity increased among EphB4-positive cells. Endothelial-specific Notch1 deletion, which causes persistent hyaloid vessels, accentuated this ephrin-B2-low/EphB4-high profile while reducing apoptotic labeling within residual ephrin-B2-positive cells and increasing proliferation within the EphB4-positive population. Mosaic recombination further showed that recombined endothelial cells preferentially expressed EphB4, whereas neighboring unrecombined cells more frequently retained ephrin-B2, supporting a cell-autonomous contribution of Notch1. Thus, arteriovenous-associated endothelial features remain dynamic during developmental vessel regression, linking endothelial identity to the cellular behaviors accompanying hyaloid remodeling.