Fig. 3

Localised β-catenin expression demarks feather, scutate and reticulate scale development. Whole-mount ISH for β-cat was performed to examine patterning of avian epithelial appendages. Feather patterning begins at E7, with a bifurcating dorsolateral row of feathers developing within an initiatory tract, triggering RD patterning of adjacent feathers [8] (A–D). Scutate scales form along the anterior metatarsal shank and dorsal foot surface, beginning at E10 (E–H). Restricted circular domains of β-cat preceding individual reticulate scales are visible at E10.5 along the ventral surface of the footpad and digits (I–K). These domains appear to subsequently subdivide into smaller units at E12 (L), which then form individual reticulate scales. Scale bar lengths are as follows: A, E = 2000 µm, B, C, D, I, = 1000 µm, J, K, L = 500 µm, F, G, H = 400 µm