Rectification of planar orientation angle switches behavior and replenishes contractile junctions

Area of Science:

• Developmental biology
• Cell biology
• Biophysics

Background:

• Germband elongation in early Drosophila embryos is crucial for development.
• This process relies on oriented cell intercalation via T1 transitions.
• Vertical interfaces contract and resolve into horizontal ones during T1 transitions.

Purpose of the Study:

• To investigate the mechanism of cell interface reorientation during germband elongation.
• To understand how cell interfaces acquire contractile properties.
• To elucidate how cells sustain multiple rounds of intercalation.

Main Methods:

• Live imaging of Drosophila embryos.
• Analysis of cell interface dynamics and orientation.
• Quantification of Myosin II localization.
• Perturbation of contractile molecular machinery.

Main Results:

• Cell interfaces undergo continuous angle rectification, rotating towards vertical orientations.
• Interface behavior shifts from elongating to contractile as they become more vertical.
• Vertical interfaces accumulate higher levels of Myosin II.
• Disrupting contractile machinery slows down interface rotation rates.

Conclusions:

• Angle rectification continuously replenishes the pool of contractile interfaces.
• This replenishment allows cells to participate in multiple, staggered intercalation events.
• The dynamic reinterpretation of interface identity based on orientation is key to sustained germband elongation.