a, mVISTA sequence conservation plot of the mouse Hoxa11 intron (red) with tetrapod (rat, human, chicken and frog) and fish representatives (coelacanth and zebrafish). Ex1, exon 1; Ex2, exon 2. Note that zebrafish has two Hoxa11 genes expressed in developing fins, Hoxa11a and Hoxa11b.
b, c, GFP expression in fin buds of Tg(m-Inta11-eGFP) transgenic zebrafish embryos at 60 hpf (b) and 72 hpf (c), revealing the enhancer activity of the mouse Hoxa11 intron in fish. Note the filopodia-like protrusions in GFP+ mesenchymal cells suggestive of a migration towards the fin fold. d, e,
Hoxa13a expression in developing fins at 60 hpf (d) and 72 hpf (e). Original magnification, ×400.