Mechanism of spiral waves formation in living excitable system revealed by trans-scale imaging

Abstract

Rotating spirals are typical dynamics in signal relaying systems such as neuronal seizures and cardiac fibrillations. Although properties of generated spirals have been well studied, mechanisms in their spontaneous formation have been long elusive. We here investigated the development of social amoeba, Dictyostelium discoideum, that self-organizes spiral waves of intercellular communications from a non-signaling initial state. Imaging of signaling dynamics in ~130,000 cells identified essential features to initiate, select, and maintain the spiral wave where so-called reentry, a classical concept for the spiral formation in cardiac fibrillation, played a role. Experimental and computational analysis revealed that the initiation of reentry and transition to spiral was collectively driven by anisotropic and graded growth of the signaling ability developed by repeated activities of a few pacemakers.