Topological defects in the nematic order of actin fibres as organization centres of Hydra morphogenesis

• Published in: Nature physics Vol. 17; no. 2; pp. 251 - 259
• Main Authors: Maroudas-Sacks, Yonit, Garion, Liora, Shani-Zerbib, Lital, Livshits, Anton, Braun, Erez, Keren, Kinneret
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2021; Nature Publishing Group
• Subjects: 631/57; 639/766/747; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Conjugation; Defects; Fibers; Mathematical and Computational Physics; Molecular; Morphogenesis; Optical and Plasma Physics; Physics; Physics and Astronomy; Robustness; Theoretical; Topology
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-020-01083-1

Animal morphogenesis arises from the complex interplay between multiple mechanical and biochemical processes with mutual feedback. Developing an effective, coarse-grained description of morphogenesis is essential for understanding how these processes are coordinated across scales to form robust, functional outcomes. Here we show that the nematic order of the supracellular actin fibres in regenerating Hydra defines a slowly varying field, whose dynamics provide an effective description of the morphogenesis process. We show that topological defects in this field, which are long-lived yet display rich dynamics, act as organization centres with morphological features developing at defect sites. These observations suggest that the nematic orientation field can be considered a ‘mechanical morphogen’ whose dynamics, in conjugation with various biochemical and mechanical signalling processes, result in the robust emergence of functional patterns during morphogenesis. Topological defects in the nematic order of actin fibres in a regenerating organism are shown to be tied to key feature formation. Fibre alignment sets the regenerated body axis and defect sites form organizing centres for the developing body plan.