Fig. 1

Overview on transgenic construct designs and expression patterns: (A) Constructs c1-c6 contained different fragments of the etv2 locus on chromosome 16 ranging from inclusion of the whole non-coding 4164 bp etv2-fli1b intergenic region (blue) plus the first and second exon-intron pair (purple) downstream of the transcription start site (TSS) fused to cDNA of fluorescent reporter protein mCherry in c1, a shorter 2170 bp upstream fragment plus the downstream region fused to egfp cDNA in c2, and a 2170 bp upstream fragment without the downstream exon-intron pair fused to kaede coding sequence in c3. Construct c4 contained a 100 bp more upstream sequence than c2 including the FOXC binding site (black asterisks) described by Veldman and Lin (2012), and c5 and c6 contained 3108 bp and 602 bp upstream sequences, respectively. c4-c6 also included the downstream region (equivalent to c1 and c2), and was fused to the egfp reporter. All constructs c1-c6 contained a polyadenylation signal (pA) at the 3′ end. (B) Expression patterns of c1-c6 in stable transgenic embryos around 1 dpf (25 som to prim 8 stages) were revealed by ISH. Representative embryos are oriented laterally with the head to the left. All transgenes showed robust vascular expression in head and axial vessels and the vascular plexus region recapitulating the endogenous etv2 expression pattern except for c3, which showed vascular plexus expression but reduced axial and head vessel expression. (C) At 20-22 som, endogenous etv2 expression is present in the endocardial domain of the developing cardiac disc, which was recapitulated by the c2 egfp reporter (white arrows). In contrast, the c3 kaede reporter was expressed in the myocardial domain of the early heart (white dashed circle). Embryo views are dorsal with the head to the top.