Cyclical Dermal Micro-Niche Switching Governs the Morphological Infradian Rhythm of Mouse Zigzag Hair

The study investigates the periodic morphological patterns in mouse zigzag hair, which has 3 bends, and reveals that a change in the combination of hair progenitors and their micro-niche occurs every 3 days, leading to bend formation. Chimeric loss-of-function and gain-of-function experiments on Ptn and Aff3, genes upregulated before bend formation, showed defects in the downward movement of the micro-niche and the rhythm of bend formation. This demonstrates that the periodic change between progenitors and micro-niche is crucial for the unique infradian rhythm of zigzag hair.