Kinesin-3 drives the transport of synaptic vesicle precursors to axon terminals. Loss of the Caenorhabditis elegans protein Unc104, eqivalent to human KIF1A, results in decreased synaptic vesicles in axonal growth cones. In mice loss of KIF1A caused severe motor and sensory abnormalities associated with neuronal cell death (Yonekawa et al. 1998). Kinesin-3 is often described as monomeric, but has recently been shown to be functionally dimeric (Hammond et al. 2009).