Plays an important role in the reorganization of the actin cytoskeleton. Binds to and sequesters actin monomers (G actin). Nucleates actin polymerization by assembling three actin monomers in cross-filament orientation and thereby promotes growth of actin filaments at the barbed end. Can also mediate actin depolymerization at barbed ends and severing of actin filaments. Promotes formation of cell ruffles. Regulates neuron morphogenesis and increases branching of axons and dendrites (By similarity). Required for normal embryonic development, including normal development of laterality, normal body size and shape, as well as normal brain, heart and kidney development. Required for normal development of stereocilia and kinocilia in sensory hair cells of neuromasts in the posterior lateral line organ, and thus also for balance keeping and normal swimming behavior. Interacts with pacsin1. Detected throughout the neuron cell body, as well as in axons and dendrites (By similarity). Colocalizes with the actin cytoskeleton. Recruited to the cell membrane via interaction with pacsin1. Detected at the apical surface of cells at the basis of forming cilia, but not in the cilia themselves. Detected in early zygote. Detected in neural keel and in Kupffer's vesicle at the eight somite stage. Detected in developing pronephric tubules, the otic vesicle and nasal placodes at 24 hpf. At 24 to 72 hpf, detected in ciliated epithelium cells of the neural tube, nasal pits and pronephric tubules. Detected in embryonic neuronal tissues, including forebrain, hindbrain, spinal cord and retina.