Cell ratcheting through the Sbf RabGEF directs force balancing and stepped apical constriction

Area of Science:

• Cell Biology
• Developmental Biology
• Biophysics

Background:

• Drosophila gastrulation involves pulsed apical constriction for mesoderm invagination.
• Maintaining uniform epithelial behavior during pulsed events is crucial for development.

Purpose of the Study:

• To elucidate the mechanisms ensuring irreversibility of pulsed cellular events during Drosophila gastrulation.
• To identify the molecular players involved in organizing the apical surface for efficient cell shape changes.

Main Methods:

• Mean Squared Displacement (MSD)-based analyses to identify contractile steps.
• Genetic disruption of the Sbf/Rab35 trafficking pathway.
• Microscopy to observe apical plasma membrane morphology and cell behaviors.
• Endosomal pathway analysis involving Rab5 and Rab11.

Main Results:

• Disruption of the Sbf/Rab35 pathway leads to reversible contractile steps and abnormal apical membrane convolution.
• Sbf/Rab35 is essential for organizing the apical surface and facilitating Myosin function.
• Sbf/Rab35/CME directs plasma membrane to Rab11 endosomes via Rab5 endosomes.

Conclusions:

• Sbf/Rab35 and CME act as a ratcheting mechanism, moving excess membrane into endosomal pathways.
• This process allows for actomyosin network and apical surface reshaping, ensuring developmental progression.