Four studies identify alternative origins for cells of the developing lymphatic system, challenging the long-standing view that they all come from veins.
For 10 years, Karina Yaniv has worked to find out just how much zebrafish have in common with mice—at least when it comes to their lymphatic systems, the open-ended networks of vessels best known for draining fluids from tissues and providing thoroughfares for immune cells throughout the body. Yet in doing so she ended up discovering something that had very little in common with the findings of numerous earlier studies on other animals’ lymphatic systems. Contrary to the widely held view in developmental biology, she found, lymphatics don’t always originate from veins.
“It was scary—I’m a young PI, so it’s not easy to stand up against the stream,” says Yaniv, who studies developmental biology at the Weizmann Institute of Science in Rehovot, Israel. But it turns out she isn’t the only one. Within three months of each other, two other independent groups published their unexpected findings supporting new roles for nonvenous progenitor cells in lymphatic development.