Iguchi, R.; Kita, T.; Watanabe, T.; Chiba, K.; Niwa, S.

The axonal transport of synaptic vesicle precursors relies on KIF1A and UNC-104 ortholog motors. In mammals, KIF1B{beta} is also responsible for the axonal transport of synaptic vesicle precursors. Mutations in KIF1A and KIF1B{beta} lead to a wide range of neuropathies. While previous studies have revealed the biochemical, biophysical and cell biological properties of KIF1A, and its defects in neurological disorders, the fundamental properties of KIF1B{beta} remain elusive. In this study, we determined the motile parameters of KIF1B{beta} through single-molecule motility assays. Additionally, we established simple methods for testing the axonal transport activity of human KIF1B{beta} using Caenorhabditis elegans genetics. Taking advantage of these methods, we demonstrated that these assays enable the detection of reduced KIF1B{beta} activities both in vitro and in vivo, that is caused by a disease-associated mutation.