Fig. 4. Shox2^-/- mice exhibit impaired palatal growth in the anterior domain. Coronal sections were made in all panels. Those anterior (A,B,E,F,I,J) and posterior (C,D,G,H) to the first molar are indicated. (K and L) Sections were made through mid-level of the first molar. (A-D) At E13.5, the palatal shelves are vertically oriented in the wild type (A,C). The anterior palatal shelves (arrows) in the Shox2 mutants appear shorter and more rounded (B), but the posterior palatal shelves appear indistinguishable from the wild type (D). (E-H) At E14.5, the wild-type palatal shelves have elevated to the horizontal position above the tongue, closed and begun to fuse (E,G). The mutant palatal shelves have also elevated to the dorsum of the tongue, but have only made contact and fused in the posterior region (H). The anterior palatal shelves of the mutants appear too small to make contact at the midline, leaving an opening as indicated by a star (F). (I-L) At E15.0, palate fusion is still ongoing along the AP length in the wild-type embryo (I,K). A cleft (star) remains in the anterior palate of Shox2 mutants (J). A section through the mid-level of the first molar of the mutant shows the anterior contact point (arrow) of the palatal shelves (L). Inset in L shows disruption of the midline seam (arrowheads) in the posterior palate of the mutant at E15.0. T, tongue; PS, palatal shelves; th, tooth. Scale bar: 300 µm.