Fig. S1

foxc1b expression is faithfully reported by the foxc1b:EGFP transgenic line in the zebrafish ventral head. A-F) 2 dpf and G-N) 4 dpf images of foxc1b expression in lateral (A-D, G-L) and ventral views (E, F, L-N). A) foxc1b mRNA (purple) is expressed in the aortic arches, jaw, ceratohyal, and periocular mesenchyme of the ventral head of the zebrafish embryo. B) foxc1b mRNA and foxc1b:EGFP transgene expression (brown) overlap (arrows) in the ceratohyal. C) foxc1b:EGFP transgene (green) is strongly expressed in the aortic arches and mesenchyme of the ventral head. D) foxc1b mRNA expression (green) overlaps with foxc1b:EGFP antibody stain (red) in the aortic arch arteries (arrows). E) Strong expression of foxc1b:EGFP in the ventral head including the ceratohyal. F) foxc1b mRNA expression overlaps with foxc1b:EGFP antibody stain in the ceratohyal. G) At 4 dpf, foxc1b mRNA is present in the aortic arch arteries, the epibranchial region of the ventral brain, ceratohyal, swim bladder, and intestine. H) foxc1b mRNA and foxc1b:EGFP overlap in cells surrounding the aortic arch arteries. I) foxc1b:EGFP is expressed in aortic arch arteries. J) foxc1b mRNA expression overlaps with foxc1b:EGFP antibody stain in the aortic arch arteries (arrows). K) egfp mRNA and foxc1b:EGFP overlap in cells surrounding the aortic arch arteries (arrows). L) foxc1b:EGFP is expressed around the ventral aorta and ceratohyal. M) foxc1b mRNA expression overlaps with foxc1b:EGFP antibody stain in the ventral aorta (arrows) and ceratohyal. N) egfp mRNA and foxc1b:EGFP overlap in cells surrounding the ventral aorta (arrows) and ceratohyal. Scale bars in A and G represent 200 µm. Scale bars in B and H represent 20 µm. Scale bars in C-F and I-N represent 50 µm.­ Insets in D, F, J, K, M and N show merged, foxc1b or egfp F-ISH (green), and foxc1b:EGFP (shown in red) antibody stain. AAA = aortic arch arteries, CH = ceratohyal, VA = ventral aorta.