Mechanical Coupling between Endoderm Invagination and Axis Extension in Drosophila

Area of Science:

• Developmental Biology
• Biophysics
• Cell Biology

Background:

• Understanding how genetic programs generate cell-intrinsic forces for embryonic shaping is key.
• Less is known about how tissue-scale physical forces influence morphogenesis, particularly during axis extension.

Purpose of the Study:

• To investigate the role of extrinsic physical forces in Drosophila germband extension (GBE).
• To identify the source of tensile forces driving anteroposterior (AP) cell elongation during GBE.

Main Methods:

• Cell tracking and apical deformation quantification to analyze AP cell elongation patterns.
• Light sheet microscopy to map gastrulation movements.
• Particle Image Velocimetry and laser ablation in acellular and cellular embryos to measure forces and flows.

Main Results:

• AP cell elongation forms a posterior-culminating gradient, indicating an AP-oriented tensile force.
• Endoderm invagination, but not mesoderm invagination, is essential for this AP cell elongation gradient.
• Acellular embryos show posteriorward Myosin II flows and increased AP tension in the posterior endoderm, driven by apical constriction.

Conclusions:

• Apical constriction leading to endoderm invagination is the source of extrinsic forces driving germband extension.
• This study highlights the critical role of physical interactions between tissues in embryonic morphogenesis.