Analysis of intraflagellar transport in the zebrafish model

摘要

The formation and function of cilia requires that proteinsare translocated by intraflageller transport (IFT) alongmicrotubules that support ciliary structure. Using tools ofgenetic analysis in zebrafish, we studied both motors thatdrive IFT and proteins that mediate the interaction ofthe IFT particle with presumptive cargo molecules. Ourstudies demonstrate that IFT particle components, and aMeckel-Gruber Syndrome 1 (MKS1)-related, B9 domainprotein, B9d2, bind each other and contribute to the ciliarylocalization of Inversin (Nephrocystin 2). B9d2, Inversin,and Nephrocystin 5 support, in turn, the transport of acargo protein, Opsin, but not another photoreceptor ciliarytransmembrane protein, Peripherin. In parallel, we studiedmotors that drive the movement of the IFT particle, andfound that kinesin 2 family motors, kif3 and kif17, displayvery different contributions to ciliogenesis. While kif17appears largely dispensable, the kif3b gene is necessary forcilia differentiation in most tissues, although exceptionsexist, and include photoreceptors and a subset of hair cells.Cilia of these cell types persist even in kif3b/kif17 doublemutants. In contrast to kif3b/kif17 double homozygotes,simultaneous interference with kif3b and kif3c leads to thecomplete loss of photoreceptor and hair cell cilia, revealingredundancy of function. Moreover, our data suggest thatthe repertoire of kinesin motors changes in photoreceptorsduring their differentiation. These studies reveal molecularmechanisms that mediate the transport of ciliary proteins,and are of fundamental importance for the formation andfunction of several vertebrate organs.