Superresolution microscopy reveals actomyosin dynamics in medioapical arrays

Area of Science:

• Cell Biology
• Developmental Biology
• Biophysics

Background:

• Medioapical actin filament (F-actin) arrays are crucial for epithelial cell constriction and morphogenesis across species.
• Understanding the dynamic behavior and structural organization of these arrays at the molecular level is essential for deciphering developmental processes.

Purpose of the Study:

• To visualize and characterize the behavior of individual F-actin and myosin filaments within medioapical arrays during epithelial cell shape changes in Drosophila embryos.
• To elucidate the structural organization and dynamics of actomyosin networks driving morphogenesis.

Main Methods:

• Superresolution microscopy techniques, including grazing incidence structured illumination (GI-SIM) and lattice light sheet (LLSM) microscopy.
• Fluorescent labeling of F-actin and myosin filaments in live Drosophila embryos.
• Analysis of cellular morphology and actomyosin organization during dorsal closure.

Main Results:

• Actomyosin arrays form loose, apically domed meshworks in expanded cells and condense into junctional belts during contraction.
• In anisotropic cells, actin filaments align and draw closer during contraction, while in isotropic cells, they remain randomly oriented.
• Medioapical arrays are closely associated with the plasma membrane and continuous with lamellar F-actin, functioning as modified cell cortices.

Conclusions:

• Superresolution imaging provides unprecedented resolution of F-actin dynamics in embryonic tissues.
• Medioapical actomyosin arrays are dynamic structures that undergo significant rearrangement and condensation to drive cell shape changes and morphogenesis.
• These findings offer new insights into cortical architecture and the mechanisms underlying developmental tissue remodeling.