Expression of URE2-GFP reporter transgenes in zebrafish. The Tg-DrURE2 drives GFP expression in the forebrain starting at 24 hpf until at least 96 hpf (A-F). At 96 hpf GFP expression is also observed in the pharyngeal arches (E, F). The Tg-CmURE2 drives GFP expression in the forebrain at 24 hpf until at least 96 hpf (G-L). GFP expression is also first noticed in the somites and pharyngeal arches at 48 hpf (H) and 96 hpf (K, L), respectively. Panels A, B, F, G, H, L are lateral views, anterior to the left and dorsal to the top; panels C, D, E, I, J and K are ventral views. t: telencephalon; d: diencephalon. White arrowheads indicate pharyngeal arch expression and the black arrowhead indicates somite expression. Scale bar: 250 μm.