A hair-raising tale

摘要

When you are angry, cold or scared, your hairs stand up. This response is mediated by the arrector pili muscle, which runs from the bulge - the permanent portion of the hair follicle - to the skin surface. The muscle's contraction shifts the angle of the hair relative to the skin. Pilo-erection, or goosebumps, makes the hair a better insulator, and alters its appearance to send a message, gruff or bluff. Writing in Cell, Fujiwara et al.' describe how the stem cells of the bulge act as a niche for these smooth muscle cells, coordinating their differentiation and ensuring their correct localization with high reproducibility. Although piloerection still seems to occur even when the muscle cells are not attached in precisely the right position, these data provide valuable insight into stem-cell biology.