Stress fiber contraction induces cell body rotation in single keratocytes

Abstract

Single epidermal keratocytes, which are responsible for wound repair in fish, migrate while maintaining their characteristic shape: a frontal crescent-shaped lamellipodium and a posterior rugby-ball-shaped cell body. These cells are widely used in cell migration studies, especially to examine the role of actin polymerization at the leading edge of the cell. In the posterior part of the cell, stress fibers, which are bundles of actomyosin, are aligned along the seam of the ‘rugby ball.’ The ball rotates with the stress fibers during migration. The linear contraction of stress fibers appears to drive the rotation of the cell body. This review describes a conversion mechanism from linear motion to rotation driven by stress fiber contraction and soft cell body deformation, which is not found in man-made machines. We also describe a unique research method that is able to demonstrate this machinery by creating robot models. Due to their high migration rate and ease of culturing, fish keratocytes appear to be one of the best materials for studying both single cell and collective cell migration. In this review, we will also give some recent research examples of collective migration using keratocytes.

Caption of Graphical Abstract

In a migrating fish epidermal keratocyte, the cell body rotates (red arrow) with the stress fibers, which consist of contractile actomyosin bundles. Linear contraction of the stress fibers (white arrows) deforms the cell body, causing it to push the substrate (blue arrow). The reaction force (magenta arrow) then causes rotation. This process can be considered a type of linear-to-rotary conversion mechanism. Such mechanisms are used in machines, including automobile cylinder engines, and require precise motion of complex rigid parts. However, migrating keratocytes appear to have achieved a simple conversion strategy that uses their own flexibility, a characteristic of living organisms.