Fig. 6

Gene expression/PCNA analysis of early caudal denticle morphogenesis. Gene expression is shown in 30-µm transverse sections of wild-type S. canicula embryo tails post-WMISH, to highlight progressive stages of caudal denticle morphogenesis from the initial epithelial thickening. bmp4 and dlx2 expression is restricted to the mesenchyme throughout morphogenesis (Me) (a–f). shh and fgf8 are first observed in the squamous epithelium (SE) before becoming restricted to the basal epithelium (BE) (m–o, j–l). Expression of fgf3 begins in the squamous and basal epithelium and is subsequently observed throughout the epithelium and mesenchyme (g–i). PCNA immunofluorescence is observed in the epithelium and mesenchyme throughout morphogenesis (p–r). Reduced activity (marked with an arrowhead) was noted in columnar cells of the epithelium during early morphogenesis (p) and in a central region of columnar cells of the basal epithelium during later morphogenesis (q–r). This region (q) overlaps with fgf3 and shh expression in the basal epithelium (k, n) (marked with an arrowhead) and may be indicative of a basic primary enameloid knot. a is anterior, and p is posterior. Dashed lines separate the squamous epithelium (SE), basal epithelium (BE) and mesenchyme (Me). All scale bars are 50 µm in length