Required for organization of axonal microtubules, and axonal outgrowth and maintenance during peripheral and central nervous system development. Interacts with KIF1B (PubMed:16225668). Interacts with STMN2 (PubMed:20621975). Highly expressed in heart, brain, ovary, testis, spinal cord and all specific brain regions examined. Moderate expressed at intermediate level in all other adult tissues examined, as well as in fetal liver and brain. Not expressed in blood leukocytes. The disease is caused by variants affecting the gene represented in this entry. Belongs to the KIF-binding protein family. Was originally shown to localize in the mitochondrion and to play a role in mitochondrial transport (PubMed:16225668). Recent articles, however, have shown that it does not localize to mitochondria, it interacts with the cytoskeleton and does not have a role in mitochondrial function (PubMed:20621975, PubMed:23427148).