Cilia and flagella play roles in many physiological processes, including cell and fluid motility, sensory perception and development. Cilia dysfunction is linked to several human ailments, including cystic kidneys, retinal dystrophy, skeletal defects and Bardet-Biedl syndrome (BBS), which is further characterized by neurosensory impairment and obesity. The biogenesis and maintenance of cilia is driven by a conserved process termed intraflagellar transport (IFT), which is a kinesin and dynein dependent motility that occurs bidirectionally along ciliary axonemes.To identify novel ciliary components in C. elegans,, we performed serial analysis of gene expression (SAGE) from isolated ciliated cells and conducted a bioinformatics screen for nematode genes that possess the X-box promoter element, which binds the ciliogenic RFX transcription factor, DAF-19. Using these complementary approaches, we identified many candidate ciliary genes and confirmed the ciliated cell-specific expression of 14 novel genes. Analysis of the cellular distribution of three GFP-tagged putative ciliary proteins, including a retinitis pigmentosa 2 homolog, a small GTP-binding protein, and a previously uncharacterized protein (C27H5.7a), revealed localization patterns consistent with cilia-specific functions.Of particular interest is that C27H5.7a accumulates at the transition zone and undergoes IFT-like motility along the ciliary axonemes. Using a translational GFP reporter for C27H5.7a, we show that: (1) the transport rates of C27H5.7a along the ciliary axoneme are comparable to that of known IFT particle components, (2) the IFT-like motility of C27H5.7a is abrogated in IFT mutant backgrounds, and (3) C27H5.7a mislocalizes along bbs mutant cilia in a manner that is almost identical to that of known IFT components. Furthermore, we found that the Dyf and short cilia phenotype of
dyf-13(
mn396) mutants is caused by mutation in C27H5.7a. Taken together, these findings demonstrate that
dyf-13/C27H5.7a interacts genetically with the IFT and BBS pathways and is required for building an intact cilium structure. Overall, our data helps to define a ciliary transcriptome and suggests that DYF-13, an evolutionarily conserved protein, is a novel IFT component required for normal cilia function.