Fig. 2.
Increased tip cell formation in dll4+/− retinal vessels. (A and B) Isolectin B4-stained P5 dll4+/− retinal vessels show a hyperfused plexus compared with wild-type (a, artery; v, vein). (C and D) dll4+/− vessels extend many more filopodia within the vascular plexus compared with wild-type (arterial zone shown; dots indicate filopodia extensions). (E–H) Quantification of filopodial bursts at the vascular front, branchpoints in the vascular plexus, percentage of retina covered by vessels, and BrdU-labeled retinal ECs in wild-type and dll4+/−. (I–P) Whole-mount ISH shows expanded expression of tip cell marker genes pdgfb and unc5b in dll4+/− compared with wild-type (arrowheads indicate tip cell expression at vascular front). (M–P) Corresponding isolectin B4 staining of retinal vessels. Error bars, SD; ∗∗, P < 0.001, Mann–Whitney U test. [Scale bars, 250 μm (A and B); 40 μm (C and D); and 100 μm (I–P).]