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Fig. 6 Expression of putative Fgf signaling pathway components in Astyanax and zebrafish. (A-R) fgf8, dlx2b, pax9 and lhx6 expression. (A,D,G,J) Astyanax fgf8 is expressed in maxillary and mandibular epithelium of the developing mandibular arch (arrowheads), with expression domains moving medially between 42 and 48 hpf. (M) Medial limits of fgf8 expression (arrowheads) do not overlap with dlx2b expression (arrow) when detected simultaneously. (P) Zebrafish fgf8 expression resembles that in Astyanax. (B,E,H,K) Astyanax pax9 is expressed predominantly in the maxillary and mandibular mesenchyme (arrows), but is also found in patches in the oral epithelium (arrowheads). (N) Simultaneous detection of shh (arrowhead) and pax9 (arrow) indicates that pax9 mesenchymal expression is strongest lateral to the developing tooth germ (arrowhead). (Q) Zebrafish pax9 expression (arrows) resembles that in Astyanax. (C,F,I,L,O) Astyanax lhx6 is expressed in the maxillary and mandibular mesenchyme (arrows). (R) Zebrafish lhx6 expression (arrows) resembles that in Astyanax. (J-L) Sagittal sections of mandible; (N) transverse section. Abbreviations as in Fig. 1. f, forebrain; h, heart; mo, mouth opening; y, yolk. Scale bars: 100 μm.