PI(4,5)P₂ forms dynamic cortical structures and directs actin distribution as well as polarity in Caenorhabditis...

Asymmetric division is crucial for embryonic development and stem cell lineages. In the one-cell Caenorhabditis elegans embryo, a contractile cortical actomyosin network contributes to asymmetric division by segregating partitioning-defective (PAR) proteins to discrete cortical domains. In the current study, we found that the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP₂) localizes to polarized dynamic structures in C. elegans zygotes, distributing in a PAR-dependent manner along the anterior-posterior (A-P) embryonic axis. PIP₂ cortical structures overlap with F-actin, and coincide with the actin regulators RHO-1 and CDC-42, as well as ECT-2. Particle image velocimetry analysis revealed that PIP₂ and F-actin cortical movements are coupled, with PIP₂ structures moving slightly ahead of F-actin. Importantly, we established that PIP₂ cortical structure formation and movement is actin dependent. Moreover, we found that decreasing or increasing the level of PIP₂ resulted in severe F-actin disorganization, revealing interdependence between these components. Furthermore, we determined that PIP₂ and F-actin regulate the sizing of PAR cortical domains, including during the maintenance phase of polarization. Overall, our work establishes that a lipid membrane component, PIP₂, modulates actin organization and cell polarity in C. elegans embryos.