Fig. 2.

TZ exposure changes the position of the mouth and induces oral tooth formation in zebrafish. TZ treatment starting at 24 hpf results in a posteriorly positioned mouth by 78 hpf (surface staining A and B; shh^KI reporter C and D). Tooth germs are seen surrounding the mouth as visualized by the sp7 dental mesenchyme marker (GFP reporter E and F; mRNA ISH G and H) and dental epithelium marker dlx2b (mRNA ISH I and J; GFP reporter K and L). By 128 hpf, compared with a control lacking oral tooth germs (M), a TZ-exposed larva exhibits oral dental epithelial reporter expression as well as partial mineralization seen with alizarin red S staining (N and N’). By 150 hpf, compared with a control lacking oral tooth germs (O and P), a TZ-exposed larva exhibits oral dental epithelial reporter expression in a more anteriorly positioned mouth (Q and R). However, at this stage, we detect no evidence of partial mineralization. Boxed region in N is zoomed in for N’. Abbreviations: cb: ceratobranchial, m = mouth, mc = Meckel’s cartilage, mx = maxilla, op = opercle, ot = oral tooth germs/teeth, pt = pharyngeal tooth germs/teeth.