Figure 3

Differences in the tooth development according to the dosages of Spry2 and Spry4 genes. Bright field images of dissociated epithelia combined with GFP visualization of Shh expression (upper lines) supplemented with GFP only panels (lower lines) show distinct patterns of Shh signaling domains during tooth development in mouse mandible. (A-D) In specimens with similar body weights (around 270 mg), it means at the same level of the development, the dissociated epithelia in the samples with higher Spry2;Spry4 gene dosages (in orange rectangle) already show merging of R2 (red arrow) and early M1 (yellow arrow) Shh signaling domains preceding the pEK formation of prospective functional M1. In contrast, samples with lower Spry2;Spry4 gene dosages exhibit only single R2 signaling domain (E-G in red rectangle) or separate Shh signaling domains of R2 (red arrow) and M1 (yellow arrow) (H-I in blue rectangle). (J-N) The persisting R2 rudiment in the genotypes with lower Spry2;Spry4 gene dosages gives rise to a supernumerary tooth primordium (S, black arrow) in front of M1 at later stages (in green rectangle). Anterior direction is on the left side (the scale bar is 100 μm).