Fig. 8

Gene expression analysis of putative placode GRN members, during general body denticle development. Section in situ hybridisation (SISH) was undertaken during early development of body denticles. Expression of shh was epithelial throughout development (a–c), whereas fgf3 was observed in both the epithelium and mesenchyme (d–f). bmp4 was mesenchymal throughout early morphogenesis (g–i). PCNA immunoreactivity was observed in the epithelial cells and condensing mesenchyme of emerging denticles (j–l). Reduced immunoreactivity was noted in columnar cells of the basal epithelium during placode formation (j) (white arrowed). fgf3 and shh expression marks enameloid knot-like cells of the epithelium associated with denticle morphogenesis (c, f), which also show reduced PCNA immunoreactivity (l), characteristic of this signalling centre (black arrowheads). The dashed line separates the epithelium from the underlying mesenchyme (a–i), as well as the basal epithelium and squamous epithelium (j–l). All scale bars are 50 µm in length except for image i for which the scale bar is 100 µm