Hierarchical Patterning Modes Orchestrate Hair Follicle Morphogenesis

The study explored the mechanisms behind hair follicle patterning, focusing on two theories: the Turing reaction-diffusion system and mesenchymal self-organisation. Researchers identified a network of FGF, WNT, and BMP signalling interactions that could spontaneously create periodic patterns. Time-lapse imaging showed that mesenchymal cell condensation at hair follicles was directed by an epidermal prepattern. However, when high FGF and low BMP activity were applied across the skin, mesenchymal cells demonstrated a capacity for self-organisation without epithelial guidance. This self-organisation depended on restricted TGF β signalling, which facilitated chemotactic patterning when reaction-diffusion was suppressed. The study highlighted a hierarchy of patterning modes in organogenesis.