Sox7/Sox18 morphants display abnormal arterial–venous specification and arteriovenous shunts. Except in panels I,J, all embryos shown resulted of injection of regular doses of control or Sox7/Sox18 morpholinos (4 ng of each) and are fixed at 28 hpf. Pictures and sections are made at the trunk level. (A–D) In situ staining with the venous-specific marker Flt4 shows an ectopic expression in the dorsal aorta while the domain corresponding to the artery-specific marker EphrinB2a (panels E–H) is reduced. Panels C,D,G,H are confocal images of transverse sections of fluorescent embryos labeled by in situ. (I,J) Transverse sections of embryos injected with high doses of Sox7/Sox18 morpholinos (6 ng of each). As revealed by Flt4 expression, the vein is widely expanded, at the expense of the artery. (K) Expression of the artery markers Notch3, hRT and Dll4 is not affected in double morphants. (L) There is an abolition of Gridlock expression in the double morphants within the aorta while its expression in the brain was not affected. (M) White arrows mark the proximal aorta at the level where the paired lateral dorsal aortae normally fused into a single tube. 28 hpf Tg(fli1:EGFP)Y1 control fishes show well differentiated proximal aorta whereas morphants display strong dysmorphogenesis of the proximal aorta. (N) Hematoxylin–eosin stained sections reveal arteriovenous shunts in the trunk region in Sox7/Sox18 morphants. NC = notochord; DA = dorsal aorta; AV = axial vein.
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