Fig. 2

The mouse Flk1in10 enhancer directs arterial-restricted expression in transgenic zebrafish. A, Schematic representation of the Flk1in10:GFP transgene. B, The mouse Flk1in10:GFP transgene directs endothelial cell-specific expression in transgenic zebrafish line tg(Flk1in10:GFP) at 24 h post fertilization (hpf). C-E, Tg(Flk1in10:GFP;kdrl:HRAS:mCherry) zebrafish expresses GFP in most endothelial cells at 30 hpf (C). At 48 hpf, GFP expression in the axial vessels becomes restricted to the dorsal aorta and to a subset of intersegmental vessels, corresponding to the developing intersegmental arteries (ISA; D; see also Movie I in the online-only Data Supplement). At 72 hpf, little dorsal aorta expression could be detected, while GFP expression is maintained in the ISA and dorsal longitudinal anastomotic vessel (E). F, Bar chart detailing GFP expression pattern in the ISA and intersegmental veins (ISVe) at 72 hpf. Represents a total of 18 embryos, ISA and ISVe identity established by using kdrl:HRAS-mCherry expression to determine whether each vessel connected to dorsal aorta or posterior cardinal vein. Any detectable level of GFP expression constituted positive, and Figure III in the online-only Data Supplement details analysis methods. bc indicates blood cells; da, dorsal aorta; dlav, dorsal longitudinal anastomotic vessel; dv, dorsal vein; GFP, green fluorescent protein; isv, intersegmental vessels; ISVe, intersegmental vein; and vv, ventral vein.