Ligand-specific endothelial Notch signaling coordinates brain pericyte specification and expansion

Pericyte specification and expansion must be coordinated with vascular growth to establish a functional cerebrovascular network, yet how endothelial signals control these distinct developmental transitions remains incompletely understood. Here, using genetic manipulation, single-cell transcriptomic analysis, and longitudinal in vivo imaging in zebrafish, we identify ligand-specific endothelial Notch signaling as a mechanism coordinating brain pericyte development. Endothelial Jag2b is required for efficient pericyte specification from pericerebral progenitor pools and subsequently promotes Notch-dependent pericyte proliferation and population expansion. By contrast, endothelial Dll4 restrains pericyte proliferation and functionally opposes Jag2b-dependent expansion, demonstrating that distinct endothelial Notch ligands generate different developmental outputs. Endothelial Notch activation increases jag2b expression, and genetic interaction analyses establish Jag2b as an important mediator of Notch-dependent pericyte expansion. Moreover, genetic disruption of piezo1 reduces brain pericyte abundance, whereas endothelial jag2b expression rescues this phenotype, placing Jag2b downstream of Piezo1-dependent hemodynamic signaling. Together, these findings reveal a ligand-specific endothelial Notch program that integrates hemodynamic cues with endothelial-pericyte communication to coordinate the specification and expansion of brain pericytes during cerebrovascular development.