The most effective plus-end-directed neuronal transporter is the kinesin-3 KIF1C, which transports large secretory vesicles and endosomes.1, 2, 3, 4 Mutations in KIF1C cause hereditary spastic paraplegia and cerebellar dysfunction in human patients.5, 6, 7, 8 In contrast to other kinesin-3s, KIF1C is a stable dimer and a highly processive motor in its native state.9 This evidence concerns the gene KIF1C and hereditary spastic paraplegia.