PI(4,5)P2forms dynamic cortical structures and directs actin distribution and cell polarity in C. elegans embryos

Abstract

AbstractAsymmetric division is crucial for embryonic development and stem cell lineages. In the one-cellC. elegansembryo, 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 inC. eleganszygotes, distributing in a polarized and PAR-dependent manner along the A-P axis. PIP2cortical structures overlap with F-actin and coincide with the actin regulators RHO-1, CDC-42 and ECT-2. Particle image velocimetry analysis revealed that PIP2and F-actin cortical movements are coupled, with PIP2structures moving slightly ahead. Importantly, we established that PIP2cortical structures form in an actin-dependent manner and, conversely, that decreasing or increasing the level of PIP2results in severe F-actin disorganization, revealing the interdependence between these components. Furthermore, we uncovered that PIP2regulates 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 inC. elegansembryos.Summary statementPI(4,5)P2is distributed in dynamic cortical structures and regulates asymmetric division by controlling actin organization and cell polarity in the one-cellC. elegansembryo.