Piezo1-Mediated Ca²⁺ Activities Regulate Brain Vascular Pathfinding during Development

During development, endothelial tip cells (ETCs) located at the leading edge of growing vascular plexus guide angiogenic sprouts to target vessels, and thus, ETC pathfinding is fundamental for vascular pattern formation in organs, including the brain. However, mechanisms of ETC pathfinding remain largely unknown. Here, we report that Piezo1-mediated Ca²⁺ activities at primary branches of ETCs regulate branch dynamics to accomplish ETC pathfinding during zebrafish brain vascular development. ETC branches display spontaneous local Ca²⁺ transients, and high- and low-frequency Ca²⁺ transients cause branch retraction through calpain and branch extension through nitric oxide synthase, respectively. These Ca²⁺ transients are mainly mediated by Ca²⁺-permeable Piezo1 channels, which can be activated by mechanical force, and mutating piezo1 largely impairs ETC pathfinding and brain vascular patterning. These findings reveal that Piezo1 and downstream Ca²⁺ signaling act as molecular bases for ETC pathfinding and highlight a novel function of Piezo1 and Ca²⁺ in vascular development.