Fig. 1.
Mesenchymal-epithelial signal exchange during hair follicle induction. Developmental stages (A–E) are represented schematically. A. Epidermal Wnts activate dermal Wnt/β-catenin signaling. B. Unknown dermal signal(s) induce an epidermal response leading to placode formation. C. Activating (green) and inhibitory (red) signals from placodes and dermal condensates (DP precursors) consolidate pattern formation through reinforcing placode/DP fate and lateral inhibition on neighboring epidermis. The network diagram depicts known hierarchies and regulatory connections between signaling pathways (as described in text). D,E. Signals regulating hair downgrowth at hair germ and peg stages.