Phosphoinositide switches in neurons: implications for membrane dynamics, axonal morphogenesis and the cortical actin cytoskeleton. During embryonic development phosphoinositides ( PI ) of the plasma membrane are instrumental in the establishment and maintenance of neuronal morphology. Of particular importance in this context are the specific distribution of PIs and the coupling of PIs to the organization of the cortical actin based cytoskeleton. In this project we will address to what extent the compositions of PIs, as well as their concentration and dynamic turnover in localized plasma membrane regions organize signal hubs and essential actin cytoskeleton dependent membrane remodeling.