PT - JOURNAL ARTICLE AU - Pelton, John C. AU - Wright, Catherine E. AU - Leitges, Michael AU - Bautch, Victoria L. TI - Multiple endothelial cells constitute the tip of developing blood vessels and polarize to promote lumen formation AID - 10.1242/dev.110296 DP - 2014 Nov 01 TA - Development PG - 4121--4126 VI - 141 IP - 21 4099 - http://dev.biologists.org/content/141/21/4121.short 4100 - http://dev.biologists.org/content/141/21/4121.full SO - Development2014 Nov 01; 141 AB - Blood vessel polarization in the apical-basal axis is important for directed secretion of proteins and lumen formation; yet, when and how polarization occurs in the context of angiogenic sprouting is not well understood. Here, we describe a novel topology for endothelial cells at the tip of angiogenic sprouts in several mammalian vascular beds. Two cells that extend filopodia and have significant overlap in space and time were present at vessel tips, both in vitro and in vivo. The cell overlap is more extensive than predicted for tip cell switching, and it sets up a longitudinal cell-cell border that is a site of apical polarization and lumen formation, presumably via a cord-hollowing mechanism. The extent of cell overlap at the tip is reduced in mice lacking aPKCĪ¶, and this is accompanied by reduced distal extension of both the apical border and patent lumens. Thus, at least two polarized cells occupy the distal tip of blood vessel sprouts, and topology, polarization and lumenization along the longitudinal border of these cells are influenced by aPKCĪ¶.