Tensile forces govern germ-layer organization in zebrafish

Area of Science:

• Developmental biology
• Cell biology
• Biophysics

Background:

• Tissue organization and cell sorting are fundamental to embryonic development.
• Previous hypotheses focused on cell adhesion and mechanical properties, but lacked validation tools.
• Measuring individual cell properties during early development is challenging.

Purpose of the Study:

• To quantify the adhesive and mechanical properties of ectoderm, mesoderm, and endoderm progenitor cells.
• To investigate the role of these properties in cell sorting during zebrafish gastrulation.
• To identify molecular mechanisms regulating cell sorting and tissue organization.

Main Methods:

• Atomic Force Microscopy (AFM) to measure cell adhesion and mechanical properties.
• In vitro self-assembly assays of progenitor cells.
• In vivo analysis of progenitor cell sorting in zebrafish embryos.
• Investigation of Nodal/TGFbeta-signalling pathways.

Main Results:

• Differential actomyosin-dependent cell-cortex tension was quantified in progenitor cells.
• Cell-cortex tension, regulated by Nodal/TGFbeta-signalling, was identified as a key driver of cell sorting.
• These findings link molecular signaling to mechanical forces in tissue organization.
• Zebrafish embryos provided a model for studying early germ layer formation.

Conclusions:

• Actomyosin-dependent cell-cortex tension regulated by Nodal/TGFbeta-signalling is crucial for germ layer organization.
• This study reveals a novel mechanism for Nodal-controlled cell-cortex tension in directing cell sorting during gastrulation.
• The findings provide new insights into the biophysical mechanisms underlying embryonic tissue patterning.