Cortical instability drives periodic supracellular actin pattern formation in epithelial tubes

Area of Science:

• Cellular and Molecular Biology
• Developmental Biology
• Biophysics

Background:

• Morphogenesis patterns can arise without predefined positional information.
• Cytoskeletal flows in the cell cortex are implicated in subcellular molecular patterning.
• Self-organization of actomyosin gels is proposed but not fully demonstrated in vivo.

Purpose of the Study:

• To investigate the self-organizing principles governing supracellular actin ring spacing in Drosophila.
• To model pattern formation from actomyosin gel dynamics in vivo.
• To validate the model's predictions using experimental perturbations.

Main Methods:

• Development of a biophysical model of actin cortex dynamics.
• Photobleaching experiments to study actin turnover and dynamics.
• Genetic and pharmacological manipulation of actomyosin gel properties.
• Analysis of actin ring spacing and movement under varying conditions.

Main Results:

• Actin ring spacing in Drosophila is governed by a self-organizing principle.
• Pattern formation depends on the interplay of myosin contractility and actin turnover.
• Perturbations altering actomyosin gel properties modified ring spacing as predicted by the model.
• Reduced cortical friction (via ECM depletion) led to dynamic, chaotic actin patterns.

Conclusions:

• A hydrodynamical instability of the actin cortex drives regular pattern formation in vivo.
• Actomyosin self-organization provides a mechanism for morphogenesis.
• The study quantitatively demonstrates self-organization principles in a living system.