Mapping Single-Cell Mechanics in the Early Embryogenesis of Xenopus laevis Using Atomic Force Microscopy

Area of Science:

• Developmental Biology
• Biophysics
• Cell Mechanics

Background:

• Early embryonic development involves cell divisions and morphological changes influenced by mechanical cues.
• The spatiotemporal mechanics of regulative embryonic cells are not well understood.

Purpose of the Study:

• To map single-cell stiffness in Xenopus laevis embryos using atomic force microscopy (AFM) from early cleavage to gastrulation.
• To investigate the mechanical heterogeneity and regional asymmetries in developing embryos.

Main Methods:

• Utilized atomic force microscopy (AFM) to measure single-cell stiffness in Xenopus laevis embryos.
• Immobilized embryos in custom grooved agarose wells after removing the vitelline membrane.
• Gently held embryos with a dulled glass pipette for stable AFM mapping.

Main Results:

• Observed significant mechanical heterogeneity in the animal hemisphere, with intrinsic stiffness variability among cells.
• Found high stiffness at cell-cell boundaries in the animal hemisphere, typical of epithelial monolayers.
• Noted lower stiffness at cell-cell boundaries in the vegetal hemisphere during gastrulation compared to cytoplasmic regions.
• Detected microscale stiff inclusions in the apical vegetal cytoplasm, comparable in size to yolk platelets.

Conclusions:

• AFM effectively probes the microscale mechanical architecture of developing regulative embryos.
• Uncovered regional mechanical asymmetries between the animal and vegetal hemispheres.
• These mechanical asymmetries likely play a role in key morphogenetic processes during early vertebrate development.