The principles underlying the biomechanics of morphogenesis are largely unknown. Epiboly is an essential embryonic event in which three tissues coordinate to direct the expansion of the blastoderm. How and where forces are generated during epiboly, and how these are globally coupled remains elusive. Here we developed a method, hydrodynamic regression (HR), to infer 3D pressure fields, mechanical power, and cortical surface tension profiles. HR is based on velocity measurements retrieved from 2D+T microscopy and their hydrodynamic modeling. We applied HR to identify biomechanically active structures and changes in cortex local tension during epiboly in zebrafish. Based on our results, we propose a novel physical description for epiboly, where tissue movements are directed by a polarized gradient of cortical tension. We found that this gradient relies on local contractile forces at the cortex, differences in elastic properties between cortex components and the passive transmission of forces within the yolk cell. All in all, our work identifies a novel way to physically regulate concerted cellular movements that might be instrumental for the mechanical control of many morphogenetic processes.
Hydrodynamic regression is used to infer mechanical parameters from microscopy data obtained during epiboly in zebrafish. This novel approach identifies a polarized gradient of cortical tension as the driver of tissue movements.
Hydrodynamic regression infers 3D pressure fields, mechanical poser, and cortical surface tension profiles during epiboly in zebrafish.
Epiboly tissue movements are directed by a polarized gradient of cortical tension.
This gradient relies on local contractile forces at the cortex, differences in elastic properties between cortex components and passive force transmission within the yolk cell.
- Received March 7, 2016.
- Revision received September 18, 2016.
- Accepted September 26, 2016.
- © 2016 The Authors