Epidermal growth factor-like domain 7 drives brain lymphatic endothelial cell development through integrin αvβ3.

In zebrafish, brain lymphatic endothelial cells (BLECs) are essential for meningeal angiogenesis and cerebrovascular regeneration. Although epidermal growth factor-like domain 7 (Egfl7) has been reported to act as a pro-angiogenic factor, its roles in lymphangiogenesis remain unclear. Here, we show that Egfl7 is expressed in both blood and lymphatic endothelial cells. We generate an egfl7 mutant with a 13-bp-deletion in exon 3 leading to reduced expression of Egfl7. The egfl7 mutant zebrafish exhibit defective formation of BLEC bilateral loop-like structures, although trunk and facial lymphatic development remains unaffected. Moreover, while the egfl7 mutant displays normal BLEC lineage specification, the migration and proliferation of these cells are impaired. Additionally, we identify integrin αvβ3 as the receptor for Egfl7. αvβ3 is expressed in the CVP and sprouting BLECs, and blocking this integrin inhibits the formation of BLEC bilateral loop-like structures. Thus, this study identifies a role for Egfl7 in BLEC development that is mediated through the integrin αvβ3.