Active torque generation by the actomyosin cell cortex drives left–right symmetry breaking

• Main Authors: Sundar Ram Naganathan, Sebastian Fürthauer, Masatoshi Nishikawa, Frank Jülicher, Stephan W Grill
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2014-12-01
• Series: eLife
• Subjects: actomyosin cortex; active torque; L/R symmetry breaking; hydrodynamics; Wnt signaling
• Online Access: https://elifesciences.org/articles/04165

Many developmental processes break left–right (LR) symmetry with a consistent handedness. LR asymmetry emerges early in development, and in many species the primary determinant of this asymmetry has been linked to the cytoskeleton. However, the nature of the underlying chirally asymmetric cytoskeletal processes has remained elusive. In this study, we combine thin-film active chiral fluid theory with experimental analysis of the C. elegans embryo to show that the actomyosin cortex generates active chiral torques to facilitate chiral symmetry breaking. Active torques drive chiral counter-rotating cortical flow in the zygote, depend on myosin activity, and can be altered through mild changes in Rho signaling. Notably, they also execute the chiral skew event at the 4-cell stage to establish the C. elegans LR body axis. Taken together, our results uncover a novel, large-scale physical activity of the actomyosin cytoskeleton that provides a fundamental mechanism for chiral morphogenesis in development.