Emergence of chiral multi-armed spirals in an open system of migrating cells under continuous cell supply.

Chemotaxis-deficient Dictyostelium discoideum KI cells form centimeter-scale clockwise multi-armed spirals, with each arm as a traveling band around a polar-ordered rotating core.

• Why it matters: Weak microscopic chiral cues in motion and interaction can bias collective coordination, but how chiral ordering emerges in open systems with continuous supply and removal is unclear.
• What they did: The authors observed KI mutants forming spirals and developed an open chiral Vicsek model, identifying intrinsic chirality, polar alignment, and continuous cell supply as key factors.
• The result: A subtle clockwise bias in single-cell migration is amplified by collective ordering into tissue-scale chirality, providing a general route for macroscopic chiral order under sustained flux.