Generation of specialized blood vessels via lymphatic transdifferentiation

The lineage and developmental trajectory of a cell are key determinant s of cellular identity. In the vascular system, endothelial cells (ECs) of blood and lymphatic vessels (LVs) differentiate and diversify to cater the different physiological demands of each organ . While LVs are known to originate from multiple origins , lymphatic ECs (LECs) themselves are not known to generate other cell - types . Here, we u s e recurrent imaging and lineage - tracing of ECs in zebrafish anal fins (AF) from early development through adulthood , to uncover an unexpected mechanism of specialized blood vessel formation through transdifferentiation of LECs . Moreover, we demonstrate distinct functional implications for deriving AF vessels from either LECs or blood ECs, uncovering a link between cell ontogeny and functionality. We further use scRNA - seq to characterize the different cellular populations and transition states involved in the transdifferentiation process . Finally, we show that akin to its normal development, the vasculature is re - derived from lymphatics during AF regeneration, demonstr ating that LECs in adult fish retain both potency and plasticity for generating blood ECs . Overall, our work highlights a new innate mechanism of blood vess el formation through LEC trans differentiation, and provides in vivo evidence for a link between cell ontogeny and functionality in ECs Overall design: 80 anal fins from immature zebrafish were digested. Sorting and RNA extraction was performed on fli1a:dsRed positive cells