A zebrafish embryo behaves both as a "cortical shell-liquid core" structure and a homogeneous solid when experiencing...

Area of Science:

• Cellular mechanics
• Biophysics
• Developmental biology

Background:

• Cellular mechanical properties are crucial for biological functions.
• A key debate exists on whether cells act as solid-like (cytoskeleton) or fluid-like (cortical shell-liquid core) under stress.
• Existing experimental methods often focus only on small-strain deformations.

Purpose of the Study:

• To investigate the mechanical behavior of zebrafish embryo cells under both small and large strain deformations.
• To resolve the debate on cellular mechanical models by examining responses across a wide range of forces.
• To analyze the role of F-actin filaments in cellular mechanical properties.

Main Methods:

• Microinjection experiments were performed on zebrafish embryo cells.
• Cellular response to varying injection forces and distances was measured.
• Mechanical properties were analyzed across small to large strain deformations.
• F-actin filament properties were examined to understand underlying mechanisms.

Main Results:

• A power law with an order of 1.5 was observed between injection force and distance, indicating homogeneous solid-like behavior at small strains.
• A linear relationship between rupture force and microinjector radius suggests membrane-like behavior at large strains.
• Analysis of F-actin filaments provided insights into the observed mechanical transitions.

Conclusions:

• Zebrafish embryo cells display a dual mechanical nature, behaving as a homogeneous solid under small deformations and a membrane-like structure under large deformations.
• The findings contribute to resolving the long-standing debate on cellular mechanical models.
• Understanding these mechanical properties is vital for cell biology and biophysics.