Cells or signals: which moves to drive skin pattern formation?

During its development, the skin produces an array of evenly spaced hair follicles. How the location of each follicle is determined to produce this pattern has been the subject of study and speculation for several decades. A central unresolved issue is the extent to which movement of scattered, precommitted follicle cells might play a role in this process. Xavier et al. now report the identification of subpopulations of dermal cells in developing sheep skin which are positive for Delta1 expression, suggesting that these cells may represent precommitted dermal papilla cells and that dermal Notch pathway signalling plays a role in hair follicle patterning.