Heterotrimeric Kinesin-2 (KIF3) Mediates Transition Zone and Axoneme Formation of Mouse Photoreceptors

Abstract Anterograde intraflagellar transport (IFT) employing kinesin-2 molecular motors has been implicated in trafficking of photoreceptor outer segment proteins. We generated embryonic retina-specific (prefix emb) and tamoxifen-induced (prefix tam) deletions of KIF3a and IFT88 in adult mice to study photoreceptor ciliogenesis and protein trafficking. In embKif3a-/- and in embIft88-/- mice, basal bodies failed to extend transition zones (connecting cilia) with outer segments (OS), and visual pigments mistrafficked. In contrast, tamKif3a-/- and tamIft88-/- photoreceptor axonemes disintegrated slowly post-induction, starting distally, but rhodopsin and cone pigments trafficked normally for more than two weeks, a time interval during which the OS is completely renewed. The results demonstrate that visual pigments transport to the ROS despite removal of KIF3 and IFT88, and KIF3-mediated anterograde IFT is responsible for photoreceptor transition zone (PTZ) and axoneme formation.