FIGURE 3.

Expression pattern of Pitx2 at later stages of axolotl odontogenesis. Pitx2 expression becomes gradually restricted to individual tooth germs (arrows mark initiator-tooth germs of respective tooth fields and arrowheads mark sequentially added tooth germs). (A,C,E) Within the mouth roof epithelium, the initial Pitx2 expression delineating individual tooth fields (black broken lines in A) becomes focused into individual tooth germs, inter-germ regions, and the forming successional dental laminae of vomerine (vom) and palatine (pal) tooth fields (C,E). Pitx2 expression is further associated with the developing premaxillary tooth field (pmx), although individual tooth germs cannot be discerned. (B,D,F) Within the mouth floor epithelium, strong Pitx2 expression is visible in the developing tooth germs of dentary (den) and coronoid (cor) tooth fields. cor, coronoid tooth field; den, dentary tooth field; pal, palatine tooth field; pmx, premaxillary tooth field; vom, vomerine tooth field. Scale bars equal 500 μm (scale bar in B is valid for A,B, scale bar in F is valid for C–F).