PI(4,5)P2 forms dynamic cortical structures and directs actin distribution and cell 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 anterior-posterior (A-P) polarity and asymmetric division by segregating PAR proteins to discrete cortical domains. Here, we discovered that the plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) forms dynamic structures in C. elegans zygotes, distributing in a polarized and PAR-dependent manner along the A-P axis. PIP2 cortical structures overlap with F-actin and coincide with the actin regulators RHO-1, CDC-42 and ECT-2. Particle image velocimetry analysis revealed that PIP2 and F-actin cortical movements are coupled, with PIP2 structures moving slightly ahead. Importantly, we established that PIP2 cortical structures form in an actin-dependent manner and, conversely, that decreasing or increasing the level of PIP2 results in severe F-actin disorganization, revealing the interdependence between these components. Furthermore, we uncovered that PIP2 regulates the sizing of PAR cortical domains. Overall, our work establishes for the first time that a lipid membrane component, PIP2, is a critical modulator of actin organization and cell polarity in C. elegans embryos.\n\nSummary statementPI(4,5)P2 is distributed in dynamic cortical structures and regulates asymmetric division by controlling actin organization and cell polarity in the one-cell C. elegans embryo.