Chemokine Signaling Directs Trunk Lymphatic Network Formation along the Preexisting Blood Vasculature

The lymphatic system is crucial for fluid homeostasis, immune responses, and numerous pathological processes. However, the molecular mechanisms responsible for establishing the anatomical form of the lymphatic vascular network remain largely unknown. Here, we show that chemokine signaling provides critical guidance cues directing early trunk lymphatic network assembly and patterning. The chemokine receptors Cxcr4a and Cxcr4b are expressed in lymphatic endothelium, whereas chemokine ligands Cxcl12a and Cxcl12b are expressed in adjacent tissues along which the developing lymphatics align. Loss- and gain-of-function studies in zebrafish demonstrate that chemokine signaling orchestrates the stepwise assembly of the trunk lymphatic network. In addition to providing evidence for a lymphatic vascular guidance mechanism, these results also suggest a molecular basis for the anatomical coalignment of lymphatic and blood vessels. ► Cxcr4a and Cxcr4b are expressed in lymphatic endothelium ► Cxcl12a and Cxcl12b are expressed in adjacent tissues along which lymphatics migrate ► Chemokine signaling coordinates the stepwise assembly of the trunk lymphatic network Cha et al. find that chemokine signaling guides the migration of lymphatic endothelial cells in developing zebrafish embryos. Chemokine signals are essential for the stereotypic assembly and patterning of the trunk lymphatic network and provide a molecular mechanism for the anatomical coalignment of lymphatic and blood vessels.