Component of the intraflagellar transport (IFT) complex B required for transport of proteins in the motile cilium. Required for transport of specific ciliary cargo proteins related to motility, while it is neither required for IFT complex B assembly or motion nor for cilium assembly. Required for efficient coupling between the accumulation of GLI2 and GLI3 at the ciliary tips and their dissociation from the negative regulator SUFU (PubMed:22718903, PubMed:25340710). Plays a key role in maintaining the integrity of the IFT complex B and the proper ciliary localization of the IFT complex B components. Not required for IFT complex A ciliary localization or function. Essential for maintaining proper microtubule organization within the ciliary axoneme (PubMed:28264835). Component of the IFT complex B. Interacts with IFT46; the interaction is direct. Localizes at the base to the ciliary transition zone. High expression detected in testis. Detected also retina, kidney, lung and brain tissue. The expression level is low in spleen (PubMed:22718903). Expressed in the developing liver (PubMed:31595528). Present in the airway epithelial cells and the testes (at protein level) (PubMed:25340710). Expressed during early development stages (12.5 dpc, 13.5 dpc, and 14.5 dpc). Partial embryonic lethality and patterning defects. Surviving mice show hopping gait, polydactyly, hydrocephalus, and male sterility. Impaired hedgehog signaling. Primary cilia are not reduced in number and their length is normal (PubMed:25340710). Mice exhibit defective cilia structure, including abnormal positioning and number of ciliary microtubule doublets, abnormal localization of IFT complex B components and significantly reduced ciliary tip accumulation of proteins GLI2 and GLI3 (PubMed:28264835). Belongs to the IFT56 family.