Required for organization of axonal microtubules, and axonal outgrowth and maintenance during peripheral and central nervous system development. Regulates mitochondrial transport by modulating KIF1B motor activity. Defects in KIAA1279 are the cause of Goldberg-Shprintzen megacolon syndrome (GOSHS). GOSHS is characterized by microcephaly, mental retardation and facial dysmorphism, as well as phenotypes related to Hirschsprung disease syndrome. Belongs to the KIF1-binding protein family. Note: This description may include information from UniProtKB.