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

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