This entry includes tetratricopeptide repeat proteins 21A (TTC21A) and 21B (TTC21B), and other homologues with numerous tetratricopeptide repeats. TTC21B is a component of the IFT complex A (IFT-A), which is required for retrograde ciliary transport. Intraflagellar transport (IFT) is required for cilium assembly and trafficking within cilia []. Several diseases results from mutations in the TTC21B gene including nephronophthisis 12, short-rib thoracic dysplasia 4 with or without polydactyly, and Joubert syndrome 11 [].
