Myosin1D directs circumferential F-actin flow to define cell chirality

Eukaryotic cells possess intrinsic chirality in their structure, motility, and intracellular dynamics, known as cell chirality, which contributes to left–right asymmetric morphogenesis. However, the mechanisms underlying its formation remain elusive. In Drosophila, Myosin1D (Myo1D) and Myosin1C (Myo1C), respectively, dictate right-handed or left-handed chirality of the cell shape and body. Here, we report that Myo1D and Myo1C, respectively, directed clockwise and counterclockwise circumferential F-actin flows in Drosophila macrophages collaborating with Myosin2 (Myo2). Furthermore, Myo1C induced a random F-actin flow in an in vitro motility assay, whereas Myo1D triggered the self-organization of the F-actin ring rotating clockwise in the same conditions, implying that Myo1D assembles F-actin into a circular arrangement with barbed-end-to-pointed-end polarity aligned in a specific direction. We propose a model in which Myo1D induces the formation of F-actin structures aligned in such a polarized fashion within macrophages, and Myo2 rotates them clockwise. This model provides a molecular basis for the formation of cell and organ chirality.