Cortical microtubules oppose actomyosin-driven membrane ingression during

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Biology

Background:

• During C. elegans oocyte meiosis I, a contractile ring assembles within a larger cortical actomyosin network.
• This network mediates ring dynamics and controls membrane ingression during polar body extrusion.
• CLS-2, a microtubule-stabilizing protein, was previously proposed to balance actomyosin tension and microtubule stiffness for ring assembly.

Approach:

• Live cell imaging and fluorescent protein fusions were used to study CLS-2 and associated proteins.
• The functions of CLS-2, KNL-1, and BUB-1 were investigated by reducing their activity.
• Microtubule stability was manipulated using nocodazole and taxol treatments.

Key Points:

• CLS-2, KNL-1, and BUB-1 are part of a kinetochore protein complex co-localizing to cortical patches during oocyte meiosis I.
• These proteins are essential for cortical microtubule stability, limiting membrane ingression, and facilitating polar body extrusion.
• Altering microtubule stability (destabilization or stabilization) directly impacts membrane ingression and polar body extrusion success.

Conclusions:

• CLS-2, as part of a kinetochore sub-complex, stabilizes microtubules to stiffen the oocyte cortex.
• This cortical stiffening limits overall membrane ingression, crucial for contractile ring function.
• Successful polar body extrusion during meiosis I relies on this balance of microtubule-mediated stiffness and actomyosin dynamics.