Morphology of the palate in <i>Fras1^+/+</i> (A,C,E and G) and <i>Fras1^bfb/bfb</i> (B,D,F and H) mice.

<p>At E18.5 the palate has fused completely in all wildtype foetuses (A) but a proportion of <i>Fras1^bfb/bfb</i> mice have an overt palatal cleft (B). The palatal shelves have elevated and become closely opposed in wildtype mice (C) while there is a significant delay in palatal shelf growth in <i>Fras1^bfb/bfb</i> embryos (D). At E15.5 there is a complete fusion between the palatal shelves and nasal septum in wildtype mice (E) while a subtle palatal blister is evident in 80% of E15.5 <i>Fras1^bfb/bfb</i> embryos (arrowhead, F). <i>TGFβ3</i> is strongly expressed in palatal shelf epithelium (arrow) of both wildtype (G) and <i>Fras1^bfb/bfb</i> mutants (H) but is aberrantly expressed in the nasal septum epithelium (arrowhead) in mutants. NC, nasal cavity; NS, nasal septum; VN, vomeronasal organ; T, tongue; MC, Meckel's cartilage, PS, palatal shelf.