Non-junctional E-Cadherin Clusters Regulate the Actomyosin Cortex in the C. elegans Zygote

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Cell Biology

Background:

• Classical cadherins mediate cell-cell adhesion via extracellular domains and intracellular actin connections.
• Adhesion-independent cadherin clusters exist, but their functions remain largely unknown.
• HMR-1 is the sole classical cadherin in C. elegans, crucial for early development.

Purpose of the Study:

• To investigate the physiological roles of non-junctional cadherin clusters.
• To analyze HMR-1 function in the C. elegans zygote, a cell without neighbors.

Main Methods:

• Analysis of HMR-1 in the C. elegans zygote.
• Observation of non-junctional HMR-1 cluster formation and association with F-actin.
• Measurement of RHO-1 activity and non-muscle myosin II (NMY-2) accumulation.
• Assessment of cortical flow dynamics and cytokinesis rates.

Main Results:

• Non-junctional HMR-1 clusters form during one-cell polarization and associate with F-actin during cortical flow.
• These clusters downregulate RHO-1 activity and inhibit NMY-2 accumulation at the anterior cortex.
• HMR-1 clusters impede cortical flows, preserve actomyosin cortex integrity, and show an inverse relationship with cytokinesis rate.

Conclusions:

• Non-junctional HMR-1 clusters regulate cell cortex stability and dynamics independently of cell-cell adhesion.
• HMR-1 clusters influence RHO-1 activity and NMY-2 levels, reinforcing the actomyosin cortex.
• These clusters play a role in cell shape regulation and cytokinesis, highlighting novel cadherin functions.