Fig. 2. Effects of Dll4 knockdown on circulation and vascular pattern.
(A) Blood flow in intersegmental vessels (ISVs) of wild-type living
embryos at 3 dpf. Each line represents a set of ISVs on one side of one
embryo, scored for direction of blood flow: upward arrows (red) denote flow
from ventral to dorsal; downward arrows (blue), denote flow from dorsal to
ventral; dots represent vessels carrying no flow. (B,C) Blood
flow in intersegmental vessels of living embryos at 3 dpf injected with either
10 ng MO[Dll4] to knockdown Dll4 (B) or with 10 ng of a 5-base mismatch
control morpholino (C). (D-G) fli1:EGFP embryos at 2.5 dpf
(D,E) or 5 dpf (F,G) either uninjected (D,F) or injected with 10 ng MO[Dll4]
(E,G). White blobs (arrows in D,E) are endothelial cell nuclei. (H)
Similar region of a 2.5-dpf dll4-homozygous-mutant embryo (carrying
the fli1:EGFP transgene). (I) Endothelial cell counts in the
DAs, ISVs and DLAVs of embryos at 3 dpf. Embryos lacking Dll4 or treated with
100 µm DAPT have more cells than uninjected or DMSO-treated control
siblings. Both effects are significant at the P=0.001 level
(t-test; n
6 specimens for each treatment; error bars
represent s.e.m.). (J) fli1:EGFP embryo at 2.5 dpf injected
with 10 ng of a morpholino targeted against casanova (sox32)
to block circulation in the trunk. (K) fli1:EGFP-positive
dll4-mutant embryo at 2.5 dpf treated from 48 hpf with 2 µM SU5416
to block Vegf signalling. (L) The gut and pectoral fin vasculature of
an fli1:EGFP-positive dll4 mutant and a wild-type (normal)
sibling embryo, both at 11 dpf. Scale bar: 50 µm in D-H,J,K; 40 µm in
L.