Fig. 7. Normal differentiation of odontoblasts and altered differentiation of ameloblasts in Smo mutant teeth. Parasagittal (A,B,K,L,O,P) and frontal (C-J,M,N,Q-T) sections at 1 dpp. Sections from control (ctrl; A,C,E,G,I,K,M,O,Q,S) and mutant (mut, B,D,F,H,J,L,N,P,R,T) teeth. von Kossa staining of mineralized dentin matrix (A,B). In situ hybridization for Bmp2 (C-F), Dlx7 (G-J), DSP (K-P) and Bmp5 (Q-T). Bmp2 and DSP are expressed normally in odontoblasts in Smo mutant teeth (C-F,K-P). Dlx7 expression is severely decreased in mutant ameloblasts (G-J). DSP is expressed in preameloblasts facing predentin matrix (arrows in K and M) and is downregulated in secretory ameloblasts (a in O) in control teeth. In mutants, DSP expression is severely decreased in preameloblasts facing predentin matrix (arrows in L and N). The arrowhead in L indicates the start of decline of DSP expression in preameloblasts. Bmp5 is expressed in secretory ameloblasts (Q) and in differentiating ameloblasts (S) in control teeth. At the anterior segment of mutant incisors, Bmp5 expression is severely decreased in ameloblasts (R) but is normal in the less-mature ameloblasts in molars (T). Signals outside the tooth are sometimes due to refractile structures such as erythrocytes, cellular fragments or tissue folding. Scale bar: 200 µm.